From 216bf58f4092df33262bea498f0460657f4842a4 Mon Sep 17 00:00:00 2001 From: FUJITA Tomonori Date: Wed, 10 Mar 2010 15:23:42 -0800 Subject: Documentation: convert PCI-DMA-mapping.txt to use the generic DMA API - replace the PCI DMA API (i.e. pci_dma_*) with the generic DMA API. - make the document more generic (use the PCI specific explanation as an example). [akpm@linux-foundation.org: fix things Randy noticed] Signed-off-by: FUJITA Tomonori Cc: James Bottomley Cc: "David S. Miller" Reviewed-by: Randy Dunlap Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- Documentation/PCI/PCI-DMA-mapping.txt | 352 +++++++++++++++++----------------- 1 file changed, 172 insertions(+), 180 deletions(-) (limited to 'Documentation/PCI') diff --git a/Documentation/PCI/PCI-DMA-mapping.txt b/Documentation/PCI/PCI-DMA-mapping.txt index ecad88d9fe59..52618ab069ad 100644 --- a/Documentation/PCI/PCI-DMA-mapping.txt +++ b/Documentation/PCI/PCI-DMA-mapping.txt @@ -1,12 +1,12 @@ - Dynamic DMA mapping - =================== + Dynamic DMA mapping Guide + ========================= David S. Miller Richard Henderson Jakub Jelinek -This document describes the DMA mapping system in terms of the pci_ -API. For a similar API that works for generic devices, see +This is a guide to device driver writers on how to use the DMA API +with example pseudo-code. For a concise description of the API, see DMA-API.txt. Most of the 64bit platforms have special hardware that translates bus @@ -26,12 +26,15 @@ mapped only for the time they are actually used and unmapped after the DMA transfer. The following API will work of course even on platforms where no such -hardware exists, see e.g. arch/x86/include/asm/pci.h for how it is implemented on -top of the virt_to_bus interface. +hardware exists. + +Note that the DMA API works with any bus independent of the underlying +microprocessor architecture. You should use the DMA API rather than +the bus specific DMA API (e.g. pci_dma_*). First of all, you should make sure -#include +#include is in your driver. This file will obtain for you the definition of the dma_addr_t (which can hold any valid DMA address for the platform) @@ -78,44 +81,43 @@ for you to DMA from/to. DMA addressing limitations Does your device have any DMA addressing limitations? For example, is -your device only capable of driving the low order 24-bits of address -on the PCI bus for SAC DMA transfers? If so, you need to inform the -PCI layer of this fact. +your device only capable of driving the low order 24-bits of address? +If so, you need to inform the kernel of this fact. By default, the kernel assumes that your device can address the full -32-bits in a SAC cycle. For a 64-bit DAC capable device, this needs -to be increased. And for a device with limitations, as discussed in -the previous paragraph, it needs to be decreased. - -pci_alloc_consistent() by default will return 32-bit DMA addresses. -PCI-X specification requires PCI-X devices to support 64-bit -addressing (DAC) for all transactions. And at least one platform (SGI -SN2) requires 64-bit consistent allocations to operate correctly when -the IO bus is in PCI-X mode. Therefore, like with pci_set_dma_mask(), -it's good practice to call pci_set_consistent_dma_mask() to set the -appropriate mask even if your device only supports 32-bit DMA -(default) and especially if it's a PCI-X device. - -For correct operation, you must interrogate the PCI layer in your -device probe routine to see if the PCI controller on the machine can -properly support the DMA addressing limitation your device has. It is -good style to do this even if your device holds the default setting, +32-bits. For a 64-bit capable device, this needs to be increased. +And for a device with limitations, as discussed in the previous +paragraph, it needs to be decreased. + +Special note about PCI: PCI-X specification requires PCI-X devices to +support 64-bit addressing (DAC) for all transactions. And at least +one platform (SGI SN2) requires 64-bit consistent allocations to +operate correctly when the IO bus is in PCI-X mode. + +For correct operation, you must interrogate the kernel in your device +probe routine to see if the DMA controller on the machine can properly +support the DMA addressing limitation your device has. It is good +style to do this even if your device holds the default setting, because this shows that you did think about these issues wrt. your device. -The query is performed via a call to pci_set_dma_mask(): +The query is performed via a call to dma_set_mask(): - int pci_set_dma_mask(struct pci_dev *pdev, u64 device_mask); + int dma_set_mask(struct device *dev, u64 mask); The query for consistent allocations is performed via a call to -pci_set_consistent_dma_mask(): +dma_set_coherent_mask(): - int pci_set_consistent_dma_mask(struct pci_dev *pdev, u64 device_mask); + int dma_set_coherent_mask(struct device *dev, u64 mask); -Here, pdev is a pointer to the PCI device struct of your device, and -device_mask is a bit mask describing which bits of a PCI address your -device supports. It returns zero if your card can perform DMA -properly on the machine given the address mask you provided. +Here, dev is a pointer to the device struct of your device, and mask +is a bit mask describing which bits of an address your device +supports. It returns zero if your card can perform DMA properly on +the machine given the address mask you provided. In general, the +device struct of your device is embedded in the bus specific device +struct of your device. For example, a pointer to the device struct of +your PCI device is pdev->dev (pdev is a pointer to the PCI device +struct of your device). If it returns non-zero, your device cannot perform DMA properly on this platform, and attempting to do so will result in undefined @@ -133,31 +135,30 @@ of your driver reports that performance is bad or that the device is not even detected, you can ask them for the kernel messages to find out exactly why. -The standard 32-bit addressing PCI device would do something like -this: +The standard 32-bit addressing device would do something like this: - if (pci_set_dma_mask(pdev, DMA_BIT_MASK(32))) { + if (dma_set_mask(dev, DMA_BIT_MASK(32))) { printk(KERN_WARNING "mydev: No suitable DMA available.\n"); goto ignore_this_device; } -Another common scenario is a 64-bit capable device. The approach -here is to try for 64-bit DAC addressing, but back down to a -32-bit mask should that fail. The PCI platform code may fail the -64-bit mask not because the platform is not capable of 64-bit -addressing. Rather, it may fail in this case simply because -32-bit SAC addressing is done more efficiently than DAC addressing. -Sparc64 is one platform which behaves in this way. +Another common scenario is a 64-bit capable device. The approach here +is to try for 64-bit addressing, but back down to a 32-bit mask that +should not fail. The kernel may fail the 64-bit mask not because the +platform is not capable of 64-bit addressing. Rather, it may fail in +this case simply because 32-bit addressing is done more efficiently +than 64-bit addressing. For example, Sparc64 PCI SAC addressing is +more efficient than DAC addressing. Here is how you would handle a 64-bit capable device which can drive all 64-bits when accessing streaming DMA: int using_dac; - if (!pci_set_dma_mask(pdev, DMA_BIT_MASK(64))) { + if (!dma_set_mask(dev, DMA_BIT_MASK(64))) { using_dac = 1; - } else if (!pci_set_dma_mask(pdev, DMA_BIT_MASK(32))) { + } else if (!dma_set_mask(dev, DMA_BIT_MASK(32))) { using_dac = 0; } else { printk(KERN_WARNING @@ -170,36 +171,36 @@ the case would look like this: int using_dac, consistent_using_dac; - if (!pci_set_dma_mask(pdev, DMA_BIT_MASK(64))) { + if (!dma_set_mask(dev, DMA_BIT_MASK(64))) { using_dac = 1; consistent_using_dac = 1; - pci_set_consistent_dma_mask(pdev, DMA_BIT_MASK(64)); - } else if (!pci_set_dma_mask(pdev, DMA_BIT_MASK(32))) { + dma_set_coherent_mask(dev, DMA_BIT_MASK(64)); + } else if (!dma_set_mask(dev, DMA_BIT_MASK(32))) { using_dac = 0; consistent_using_dac = 0; - pci_set_consistent_dma_mask(pdev, DMA_BIT_MASK(32)); + dma_set_coherent_mask(dev, DMA_BIT_MASK(32)); } else { printk(KERN_WARNING "mydev: No suitable DMA available.\n"); goto ignore_this_device; } -pci_set_consistent_dma_mask() will always be able to set the same or a -smaller mask as pci_set_dma_mask(). However for the rare case that a +dma_set_coherent_mask() will always be able to set the same or a +smaller mask as dma_set_mask(). However for the rare case that a device driver only uses consistent allocations, one would have to -check the return value from pci_set_consistent_dma_mask(). +check the return value from dma_set_coherent_mask(). Finally, if your device can only drive the low 24-bits of -address during PCI bus mastering you might do something like: +address you might do something like: - if (pci_set_dma_mask(pdev, DMA_BIT_MASK(24))) { + if (dma_set_mask(dev, DMA_BIT_MASK(24))) { printk(KERN_WARNING "mydev: 24-bit DMA addressing not available.\n"); goto ignore_this_device; } -When pci_set_dma_mask() is successful, and returns zero, the PCI layer -saves away this mask you have provided. The PCI layer will use this +When dma_set_mask() is successful, and returns zero, the kernel saves +away this mask you have provided. The kernel will use this information later when you make DMA mappings. There is a case which we are aware of at this time, which is worth @@ -208,7 +209,7 @@ functions (for example a sound card provides playback and record functions) and the various different functions have _different_ DMA addressing limitations, you may wish to probe each mask and only provide the functionality which the machine can handle. It -is important that the last call to pci_set_dma_mask() be for the +is important that the last call to dma_set_mask() be for the most specific mask. Here is pseudo-code showing how this might be done: @@ -217,17 +218,17 @@ Here is pseudo-code showing how this might be done: #define RECORD_ADDRESS_BITS DMA_BIT_MASK(24) struct my_sound_card *card; - struct pci_dev *pdev; + struct device *dev; ... - if (!pci_set_dma_mask(pdev, PLAYBACK_ADDRESS_BITS)) { + if (!dma_set_mask(dev, PLAYBACK_ADDRESS_BITS)) { card->playback_enabled = 1; } else { card->playback_enabled = 0; printk(KERN_WARNING "%s: Playback disabled due to DMA limitations.\n", card->name); } - if (!pci_set_dma_mask(pdev, RECORD_ADDRESS_BITS)) { + if (!dma_set_mask(dev, RECORD_ADDRESS_BITS)) { card->record_enabled = 1; } else { card->record_enabled = 0; @@ -252,8 +253,8 @@ There are two types of DMA mappings: Think of "consistent" as "synchronous" or "coherent". The current default is to return consistent memory in the low 32 - bits of the PCI bus space. However, for future compatibility you - should set the consistent mask even if this default is fine for your + bits of the bus space. However, for future compatibility you should + set the consistent mask even if this default is fine for your driver. Good examples of what to use consistent mappings for are: @@ -285,9 +286,9 @@ There are two types of DMA mappings: found in PCI bridges (such as by reading a register's value after writing it). -- Streaming DMA mappings which are usually mapped for one DMA transfer, - unmapped right after it (unless you use pci_dma_sync_* below) and for which - hardware can optimize for sequential accesses. +- Streaming DMA mappings which are usually mapped for one DMA + transfer, unmapped right after it (unless you use dma_sync_* below) + and for which hardware can optimize for sequential accesses. This of "streaming" as "asynchronous" or "outside the coherency domain". @@ -302,8 +303,8 @@ There are two types of DMA mappings: optimizations the hardware allows. To this end, when using such mappings you must be explicit about what you want to happen. -Neither type of DMA mapping has alignment restrictions that come -from PCI, although some devices may have such restrictions. +Neither type of DMA mapping has alignment restrictions that come from +the underlying bus, although some devices may have such restrictions. Also, systems with caches that aren't DMA-coherent will work better when the underlying buffers don't share cache lines with other data. @@ -315,33 +316,27 @@ you should do: dma_addr_t dma_handle; - cpu_addr = pci_alloc_consistent(pdev, size, &dma_handle); - -where pdev is a struct pci_dev *. This may be called in interrupt context. -You should use dma_alloc_coherent (see DMA-API.txt) for buses -where devices don't have struct pci_dev (like ISA, EISA). + cpu_addr = dma_alloc_coherent(dev, size, &dma_handle, gfp); -This argument is needed because the DMA translations may be bus -specific (and often is private to the bus which the device is attached -to). +where device is a struct device *. This may be called in interrupt +context with the GFP_ATOMIC flag. Size is the length of the region you want to allocate, in bytes. This routine will allocate RAM for that region, so it acts similarly to __get_free_pages (but takes size instead of a page order). If your driver needs regions sized smaller than a page, you may prefer using -the pci_pool interface, described below. - -The consistent DMA mapping interfaces, for non-NULL pdev, will by -default return a DMA address which is SAC (Single Address Cycle) -addressable. Even if the device indicates (via PCI dma mask) that it -may address the upper 32-bits and thus perform DAC cycles, consistent -allocation will only return > 32-bit PCI addresses for DMA if the -consistent dma mask has been explicitly changed via -pci_set_consistent_dma_mask(). This is true of the pci_pool interface -as well. - -pci_alloc_consistent returns two values: the virtual address which you +the dma_pool interface, described below. + +The consistent DMA mapping interfaces, for non-NULL dev, will by +default return a DMA address which is 32-bit addressable. Even if the +device indicates (via DMA mask) that it may address the upper 32-bits, +consistent allocation will only return > 32-bit addresses for DMA if +the consistent DMA mask has been explicitly changed via +dma_set_coherent_mask(). This is true of the dma_pool interface as +well. + +dma_alloc_coherent returns two values: the virtual address which you can use to access it from the CPU and dma_handle which you pass to the card. @@ -354,54 +349,54 @@ buffer you receive will not cross a 64K boundary. To unmap and free such a DMA region, you call: - pci_free_consistent(pdev, size, cpu_addr, dma_handle); + dma_free_coherent(dev, size, cpu_addr, dma_handle); -where pdev, size are the same as in the above call and cpu_addr and -dma_handle are the values pci_alloc_consistent returned to you. +where dev, size are the same as in the above call and cpu_addr and +dma_handle are the values dma_alloc_coherent returned to you. This function may not be called in interrupt context. If your driver needs lots of smaller memory regions, you can write -custom code to subdivide pages returned by pci_alloc_consistent, -or you can use the pci_pool API to do that. A pci_pool is like -a kmem_cache, but it uses pci_alloc_consistent not __get_free_pages. +custom code to subdivide pages returned by dma_alloc_coherent, +or you can use the dma_pool API to do that. A dma_pool is like +a kmem_cache, but it uses dma_alloc_coherent not __get_free_pages. Also, it understands common hardware constraints for alignment, like queue heads needing to be aligned on N byte boundaries. -Create a pci_pool like this: +Create a dma_pool like this: - struct pci_pool *pool; + struct dma_pool *pool; - pool = pci_pool_create(name, pdev, size, align, alloc); + pool = dma_pool_create(name, dev, size, align, alloc); -The "name" is for diagnostics (like a kmem_cache name); pdev and size +The "name" is for diagnostics (like a kmem_cache name); dev and size are as above. The device's hardware alignment requirement for this type of data is "align" (which is expressed in bytes, and must be a power of two). If your device has no boundary crossing restrictions, pass 0 for alloc; passing 4096 says memory allocated from this pool must not cross 4KByte boundaries (but at that time it may be better to -go for pci_alloc_consistent directly instead). +go for dma_alloc_coherent directly instead). -Allocate memory from a pci pool like this: +Allocate memory from a dma pool like this: - cpu_addr = pci_pool_alloc(pool, flags, &dma_handle); + cpu_addr = dma_pool_alloc(pool, flags, &dma_handle); flags are SLAB_KERNEL if blocking is permitted (not in_interrupt nor -holding SMP locks), SLAB_ATOMIC otherwise. Like pci_alloc_consistent, +holding SMP locks), SLAB_ATOMIC otherwise. Like dma_alloc_coherent, this returns two values, cpu_addr and dma_handle. -Free memory that was allocated from a pci_pool like this: +Free memory that was allocated from a dma_pool like this: - pci_pool_free(pool, cpu_addr, dma_handle); + dma_pool_free(pool, cpu_addr, dma_handle); -where pool is what you passed to pci_pool_alloc, and cpu_addr and -dma_handle are the values pci_pool_alloc returned. This function +where pool is what you passed to dma_pool_alloc, and cpu_addr and +dma_handle are the values dma_pool_alloc returned. This function may be called in interrupt context. -Destroy a pci_pool by calling: +Destroy a dma_pool by calling: - pci_pool_destroy(pool); + dma_pool_destroy(pool); -Make sure you've called pci_pool_free for all memory allocated +Make sure you've called dma_pool_free for all memory allocated from a pool before you destroy the pool. This function may not be called in interrupt context. @@ -411,15 +406,15 @@ The interfaces described in subsequent portions of this document take a DMA direction argument, which is an integer and takes on one of the following values: - PCI_DMA_BIDIRECTIONAL - PCI_DMA_TODEVICE - PCI_DMA_FROMDEVICE - PCI_DMA_NONE + DMA_BIDIRECTIONAL + DMA_TO_DEVICE + DMA_FROM_DEVICE + DMA_NONE One should provide the exact DMA direction if you know it. -PCI_DMA_TODEVICE means "from main memory to the PCI device" -PCI_DMA_FROMDEVICE means "from the PCI device to main memory" +DMA_TO_DEVICE means "from main memory to the device" +DMA_FROM_DEVICE means "from the device to main memory" It is the direction in which the data moves during the DMA transfer. @@ -427,12 +422,12 @@ You are _strongly_ encouraged to specify this as precisely as you possibly can. If you absolutely cannot know the direction of the DMA transfer, -specify PCI_DMA_BIDIRECTIONAL. It means that the DMA can go in +specify DMA_BIDIRECTIONAL. It means that the DMA can go in either direction. The platform guarantees that you may legally specify this, and that it will work, but this may be at the cost of performance for example. -The value PCI_DMA_NONE is to be used for debugging. One can +The value DMA_NONE is to be used for debugging. One can hold this in a data structure before you come to know the precise direction, and this will help catch cases where your direction tracking logic has failed to set things up properly. @@ -442,21 +437,21 @@ potential platform-specific optimizations of such) is for debugging. Some platforms actually have a write permission boolean which DMA mappings can be marked with, much like page protections in the user program address space. Such platforms can and do report errors in the -kernel logs when the PCI controller hardware detects violation of the +kernel logs when the DMA controller hardware detects violation of the permission setting. Only streaming mappings specify a direction, consistent mappings implicitly have a direction attribute setting of -PCI_DMA_BIDIRECTIONAL. +DMA_BIDIRECTIONAL. The SCSI subsystem tells you the direction to use in the 'sc_data_direction' member of the SCSI command your driver is working on. For Networking drivers, it's a rather simple affair. For transmit -packets, map/unmap them with the PCI_DMA_TODEVICE direction +packets, map/unmap them with the DMA_TO_DEVICE direction specifier. For receive packets, just the opposite, map/unmap them -with the PCI_DMA_FROMDEVICE direction specifier. +with the DMA_FROM_DEVICE direction specifier. Using Streaming DMA mappings @@ -467,43 +462,43 @@ scatterlist. To map a single region, you do: - struct pci_dev *pdev = mydev->pdev; + struct device *dev = &my_dev->dev; dma_addr_t dma_handle; void *addr = buffer->ptr; size_t size = buffer->len; - dma_handle = pci_map_single(pdev, addr, size, direction); + dma_handle = dma_map_single(dev, addr, size, direction); and to unmap it: - pci_unmap_single(pdev, dma_handle, size, direction); + dma_unmap_single(dev, dma_handle, size, direction); -You should call pci_unmap_single when the DMA activity is finished, e.g. +You should call dma_unmap_single when the DMA activity is finished, e.g. from the interrupt which told you that the DMA transfer is done. Using cpu pointers like this for single mappings has a disadvantage, you cannot reference HIGHMEM memory in this way. Thus, there is a -map/unmap interface pair akin to pci_{map,unmap}_single. These +map/unmap interface pair akin to dma_{map,unmap}_single. These interfaces deal with page/offset pairs instead of cpu pointers. Specifically: - struct pci_dev *pdev = mydev->pdev; + struct device *dev = &my_dev->dev; dma_addr_t dma_handle; struct page *page = buffer->page; unsigned long offset = buffer->offset; size_t size = buffer->len; - dma_handle = pci_map_page(pdev, page, offset, size, direction); + dma_handle = dma_map_page(dev, page, offset, size, direction); ... - pci_unmap_page(pdev, dma_handle, size, direction); + dma_unmap_page(dev, dma_handle, size, direction); Here, "offset" means byte offset within the given page. With scatterlists, you map a region gathered from several regions by: - int i, count = pci_map_sg(pdev, sglist, nents, direction); + int i, count = dma_map_sg(dev, sglist, nents, direction); struct scatterlist *sg; for_each_sg(sglist, sg, count, i) { @@ -527,16 +522,16 @@ accessed sg->address and sg->length as shown above. To unmap a scatterlist, just call: - pci_unmap_sg(pdev, sglist, nents, direction); + dma_unmap_sg(dev, sglist, nents, direction); Again, make sure DMA activity has already finished. -PLEASE NOTE: The 'nents' argument to the pci_unmap_sg call must be - the _same_ one you passed into the pci_map_sg call, +PLEASE NOTE: The 'nents' argument to the dma_unmap_sg call must be + the _same_ one you passed into the dma_map_sg call, it should _NOT_ be the 'count' value _returned_ from the - pci_map_sg call. + dma_map_sg call. -Every pci_map_{single,sg} call should have its pci_unmap_{single,sg} +Every dma_map_{single,sg} call should have its dma_unmap_{single,sg} counterpart, because the bus address space is a shared resource (although in some ports the mapping is per each BUS so less devices contend for the same bus address space) and you could render the machine unusable by eating @@ -547,14 +542,14 @@ the data in between the DMA transfers, the buffer needs to be synced properly in order for the cpu and device to see the most uptodate and correct copy of the DMA buffer. -So, firstly, just map it with pci_map_{single,sg}, and after each DMA +So, firstly, just map it with dma_map_{single,sg}, and after each DMA transfer call either: - pci_dma_sync_single_for_cpu(pdev, dma_handle, size, direction); + dma_sync_single_for_cpu(dev, dma_handle, size, direction); or: - pci_dma_sync_sg_for_cpu(pdev, sglist, nents, direction); + dma_sync_sg_for_cpu(dev, sglist, nents, direction); as appropriate. @@ -562,27 +557,27 @@ Then, if you wish to let the device get at the DMA area again, finish accessing the data with the cpu, and then before actually giving the buffer to the hardware call either: - pci_dma_sync_single_for_device(pdev, dma_handle, size, direction); + dma_sync_single_for_device(dev, dma_handle, size, direction); or: - pci_dma_sync_sg_for_device(dev, sglist, nents, direction); + dma_sync_sg_for_device(dev, sglist, nents, direction); as appropriate. After the last DMA transfer call one of the DMA unmap routines -pci_unmap_{single,sg}. If you don't touch the data from the first pci_map_* -call till pci_unmap_*, then you don't have to call the pci_dma_sync_* +dma_unmap_{single,sg}. If you don't touch the data from the first dma_map_* +call till dma_unmap_*, then you don't have to call the dma_sync_* routines at all. Here is pseudo code which shows a situation in which you would need -to use the pci_dma_sync_*() interfaces. +to use the dma_sync_*() interfaces. my_card_setup_receive_buffer(struct my_card *cp, char *buffer, int len) { dma_addr_t mapping; - mapping = pci_map_single(cp->pdev, buffer, len, PCI_DMA_FROMDEVICE); + mapping = dma_map_single(cp->dev, buffer, len, DMA_FROM_DEVICE); cp->rx_buf = buffer; cp->rx_len = len; @@ -606,25 +601,25 @@ to use the pci_dma_sync_*() interfaces. * the DMA transfer with the CPU first * so that we see updated contents. */ - pci_dma_sync_single_for_cpu(cp->pdev, cp->rx_dma, - cp->rx_len, - PCI_DMA_FROMDEVICE); + dma_sync_single_for_cpu(&cp->dev, cp->rx_dma, + cp->rx_len, + DMA_FROM_DEVICE); /* Now it is safe to examine the buffer. */ hp = (struct my_card_header *) cp->rx_buf; if (header_is_ok(hp)) { - pci_unmap_single(cp->pdev, cp->rx_dma, cp->rx_len, - PCI_DMA_FROMDEVICE); + dma_unmap_single(&cp->dev, cp->rx_dma, cp->rx_len, + DMA_FROM_DEVICE); pass_to_upper_layers(cp->rx_buf); make_and_setup_new_rx_buf(cp); } else { /* Just sync the buffer and give it back * to the card. */ - pci_dma_sync_single_for_device(cp->pdev, - cp->rx_dma, - cp->rx_len, - PCI_DMA_FROMDEVICE); + dma_sync_single_for_device(&cp->dev, + cp->rx_dma, + cp->rx_len, + DMA_FROM_DEVICE); give_rx_buf_to_card(cp); } } @@ -634,19 +629,19 @@ Drivers converted fully to this interface should not use virt_to_bus any longer, nor should they use bus_to_virt. Some drivers have to be changed a little bit, because there is no longer an equivalent to bus_to_virt in the dynamic DMA mapping scheme - you have to always store the DMA addresses -returned by the pci_alloc_consistent, pci_pool_alloc, and pci_map_single -calls (pci_map_sg stores them in the scatterlist itself if the platform +returned by the dma_alloc_coherent, dma_pool_alloc, and dma_map_single +calls (dma_map_sg stores them in the scatterlist itself if the platform supports dynamic DMA mapping in hardware) in your driver structures and/or in the card registers. -All PCI drivers should be using these interfaces with no exceptions. -It is planned to completely remove virt_to_bus() and bus_to_virt() as +All drivers should be using these interfaces with no exceptions. It +is planned to completely remove virt_to_bus() and bus_to_virt() as they are entirely deprecated. Some ports already do not provide these as it is impossible to correctly support them. Optimizing Unmap State Space Consumption -On many platforms, pci_unmap_{single,page}() is simply a nop. +On many platforms, dma_unmap_{single,page}() is simply a nop. Therefore, keeping track of the mapping address and length is a waste of space. Instead of filling your drivers up with ifdefs and the like to "work around" this (which would defeat the whole purpose of a @@ -655,7 +650,7 @@ portable API) the following facilities are provided. Actually, instead of describing the macros one by one, we'll transform some example code. -1) Use DECLARE_PCI_UNMAP_{ADDR,LEN} in state saving structures. +1) Use DEFINE_DMA_UNMAP_{ADDR,LEN} in state saving structures. Example, before: struct ring_state { @@ -668,14 +663,11 @@ transform some example code. struct ring_state { struct sk_buff *skb; - DECLARE_PCI_UNMAP_ADDR(mapping) - DECLARE_PCI_UNMAP_LEN(len) + DEFINE_DMA_UNMAP_ADDR(mapping); + DEFINE_DMA_UNMAP_LEN(len); }; - NOTE: DO NOT put a semicolon at the end of the DECLARE_*() - macro. - -2) Use pci_unmap_{addr,len}_set to set these values. +2) Use dma_unmap_{addr,len}_set to set these values. Example, before: ringp->mapping = FOO; @@ -683,21 +675,21 @@ transform some example code. after: - pci_unmap_addr_set(ringp, mapping, FOO); - pci_unmap_len_set(ringp, len, BAR); + dma_unmap_addr_set(ringp, mapping, FOO); + dma_unmap_len_set(ringp, len, BAR); -3) Use pci_unmap_{addr,len} to access these values. +3) Use dma_unmap_{addr,len} to access these values. Example, before: - pci_unmap_single(pdev, ringp->mapping, ringp->len, - PCI_DMA_FROMDEVICE); + dma_unmap_single(dev, ringp->mapping, ringp->len, + DMA_FROM_DEVICE); after: - pci_unmap_single(pdev, - pci_unmap_addr(ringp, mapping), - pci_unmap_len(ringp, len), - PCI_DMA_FROMDEVICE); + dma_unmap_single(dev, + dma_unmap_addr(ringp, mapping), + dma_unmap_len(ringp, len), + DMA_FROM_DEVICE); It really should be self-explanatory. We treat the ADDR and LEN separately, because it is possible for an implementation to only @@ -732,15 +724,15 @@ to "Closing". DMA address space is limited on some architectures and an allocation failure can be determined by: -- checking if pci_alloc_consistent returns NULL or pci_map_sg returns 0 +- checking if dma_alloc_coherent returns NULL or dma_map_sg returns 0 -- checking the returned dma_addr_t of pci_map_single and pci_map_page - by using pci_dma_mapping_error(): +- checking the returned dma_addr_t of dma_map_single and dma_map_page + by using dma_mapping_error(): dma_addr_t dma_handle; - dma_handle = pci_map_single(pdev, addr, size, direction); - if (pci_dma_mapping_error(pdev, dma_handle)) { + dma_handle = dma_map_single(dev, addr, size, direction); + if (dma_mapping_error(dev, dma_handle)) { /* * reduce current DMA mapping usage, * delay and try again later or -- cgit v1.2.3 From 5e07c2c7301bd2c82e55cf5cbb36f7b5bddeb8e9 Mon Sep 17 00:00:00 2001 From: FUJITA Tomonori Date: Tue, 23 Mar 2010 13:35:23 -0700 Subject: Documentation: rename PCI/PCI-DMA-mapping.txt to DMA-API-HOWTO.txt This patch renames PCI/PCI-DMA-mapping.txt to DMA-API-HOWTO.txt. The commit 51e7364ef281e540371f084008732b13292622f0 "Documentation: rename PCI-DMA-mapping.txt to DMA-API-HOWTO.txt" was supposed to do this but it didn't. Signed-off-by: FUJITA Tomonori Acked-by: Randy Dunlap Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- Documentation/DMA-API-HOWTO.txt | 758 ++++++++++++++++++++++++++++++++++ Documentation/PCI/PCI-DMA-mapping.txt | 758 ---------------------------------- 2 files changed, 758 insertions(+), 758 deletions(-) create mode 100644 Documentation/DMA-API-HOWTO.txt delete mode 100644 Documentation/PCI/PCI-DMA-mapping.txt (limited to 'Documentation/PCI') diff --git a/Documentation/DMA-API-HOWTO.txt b/Documentation/DMA-API-HOWTO.txt new file mode 100644 index 000000000000..52618ab069ad --- /dev/null +++ b/Documentation/DMA-API-HOWTO.txt @@ -0,0 +1,758 @@ + Dynamic DMA mapping Guide + ========================= + + David S. Miller + Richard Henderson + Jakub Jelinek + +This is a guide to device driver writers on how to use the DMA API +with example pseudo-code. For a concise description of the API, see +DMA-API.txt. + +Most of the 64bit platforms have special hardware that translates bus +addresses (DMA addresses) into physical addresses. This is similar to +how page tables and/or a TLB translates virtual addresses to physical +addresses on a CPU. This is needed so that e.g. PCI devices can +access with a Single Address Cycle (32bit DMA address) any page in the +64bit physical address space. Previously in Linux those 64bit +platforms had to set artificial limits on the maximum RAM size in the +system, so that the virt_to_bus() static scheme works (the DMA address +translation tables were simply filled on bootup to map each bus +address to the physical page __pa(bus_to_virt())). + +So that Linux can use the dynamic DMA mapping, it needs some help from the +drivers, namely it has to take into account that DMA addresses should be +mapped only for the time they are actually used and unmapped after the DMA +transfer. + +The following API will work of course even on platforms where no such +hardware exists. + +Note that the DMA API works with any bus independent of the underlying +microprocessor architecture. You should use the DMA API rather than +the bus specific DMA API (e.g. pci_dma_*). + +First of all, you should make sure + +#include + +is in your driver. This file will obtain for you the definition of the +dma_addr_t (which can hold any valid DMA address for the platform) +type which should be used everywhere you hold a DMA (bus) address +returned from the DMA mapping functions. + + What memory is DMA'able? + +The first piece of information you must know is what kernel memory can +be used with the DMA mapping facilities. There has been an unwritten +set of rules regarding this, and this text is an attempt to finally +write them down. + +If you acquired your memory via the page allocator +(i.e. __get_free_page*()) or the generic memory allocators +(i.e. kmalloc() or kmem_cache_alloc()) then you may DMA to/from +that memory using the addresses returned from those routines. + +This means specifically that you may _not_ use the memory/addresses +returned from vmalloc() for DMA. It is possible to DMA to the +_underlying_ memory mapped into a vmalloc() area, but this requires +walking page tables to get the physical addresses, and then +translating each of those pages back to a kernel address using +something like __va(). [ EDIT: Update this when we integrate +Gerd Knorr's generic code which does this. ] + +This rule also means that you may use neither kernel image addresses +(items in data/text/bss segments), nor module image addresses, nor +stack addresses for DMA. These could all be mapped somewhere entirely +different than the rest of physical memory. Even if those classes of +memory could physically work with DMA, you'd need to ensure the I/O +buffers were cacheline-aligned. Without that, you'd see cacheline +sharing problems (data corruption) on CPUs with DMA-incoherent caches. +(The CPU could write to one word, DMA would write to a different one +in the same cache line, and one of them could be overwritten.) + +Also, this means that you cannot take the return of a kmap() +call and DMA to/from that. This is similar to vmalloc(). + +What about block I/O and networking buffers? The block I/O and +networking subsystems make sure that the buffers they use are valid +for you to DMA from/to. + + DMA addressing limitations + +Does your device have any DMA addressing limitations? For example, is +your device only capable of driving the low order 24-bits of address? +If so, you need to inform the kernel of this fact. + +By default, the kernel assumes that your device can address the full +32-bits. For a 64-bit capable device, this needs to be increased. +And for a device with limitations, as discussed in the previous +paragraph, it needs to be decreased. + +Special note about PCI: PCI-X specification requires PCI-X devices to +support 64-bit addressing (DAC) for all transactions. And at least +one platform (SGI SN2) requires 64-bit consistent allocations to +operate correctly when the IO bus is in PCI-X mode. + +For correct operation, you must interrogate the kernel in your device +probe routine to see if the DMA controller on the machine can properly +support the DMA addressing limitation your device has. It is good +style to do this even if your device holds the default setting, +because this shows that you did think about these issues wrt. your +device. + +The query is performed via a call to dma_set_mask(): + + int dma_set_mask(struct device *dev, u64 mask); + +The query for consistent allocations is performed via a call to +dma_set_coherent_mask(): + + int dma_set_coherent_mask(struct device *dev, u64 mask); + +Here, dev is a pointer to the device struct of your device, and mask +is a bit mask describing which bits of an address your device +supports. It returns zero if your card can perform DMA properly on +the machine given the address mask you provided. In general, the +device struct of your device is embedded in the bus specific device +struct of your device. For example, a pointer to the device struct of +your PCI device is pdev->dev (pdev is a pointer to the PCI device +struct of your device). + +If it returns non-zero, your device cannot perform DMA properly on +this platform, and attempting to do so will result in undefined +behavior. You must either use a different mask, or not use DMA. + +This means that in the failure case, you have three options: + +1) Use another DMA mask, if possible (see below). +2) Use some non-DMA mode for data transfer, if possible. +3) Ignore this device and do not initialize it. + +It is recommended that your driver print a kernel KERN_WARNING message +when you end up performing either #2 or #3. In this manner, if a user +of your driver reports that performance is bad or that the device is not +even detected, you can ask them for the kernel messages to find out +exactly why. + +The standard 32-bit addressing device would do something like this: + + if (dma_set_mask(dev, DMA_BIT_MASK(32))) { + printk(KERN_WARNING + "mydev: No suitable DMA available.\n"); + goto ignore_this_device; + } + +Another common scenario is a 64-bit capable device. The approach here +is to try for 64-bit addressing, but back down to a 32-bit mask that +should not fail. The kernel may fail the 64-bit mask not because the +platform is not capable of 64-bit addressing. Rather, it may fail in +this case simply because 32-bit addressing is done more efficiently +than 64-bit addressing. For example, Sparc64 PCI SAC addressing is +more efficient than DAC addressing. + +Here is how you would handle a 64-bit capable device which can drive +all 64-bits when accessing streaming DMA: + + int using_dac; + + if (!dma_set_mask(dev, DMA_BIT_MASK(64))) { + using_dac = 1; + } else if (!dma_set_mask(dev, DMA_BIT_MASK(32))) { + using_dac = 0; + } else { + printk(KERN_WARNING + "mydev: No suitable DMA available.\n"); + goto ignore_this_device; + } + +If a card is capable of using 64-bit consistent allocations as well, +the case would look like this: + + int using_dac, consistent_using_dac; + + if (!dma_set_mask(dev, DMA_BIT_MASK(64))) { + using_dac = 1; + consistent_using_dac = 1; + dma_set_coherent_mask(dev, DMA_BIT_MASK(64)); + } else if (!dma_set_mask(dev, DMA_BIT_MASK(32))) { + using_dac = 0; + consistent_using_dac = 0; + dma_set_coherent_mask(dev, DMA_BIT_MASK(32)); + } else { + printk(KERN_WARNING + "mydev: No suitable DMA available.\n"); + goto ignore_this_device; + } + +dma_set_coherent_mask() will always be able to set the same or a +smaller mask as dma_set_mask(). However for the rare case that a +device driver only uses consistent allocations, one would have to +check the return value from dma_set_coherent_mask(). + +Finally, if your device can only drive the low 24-bits of +address you might do something like: + + if (dma_set_mask(dev, DMA_BIT_MASK(24))) { + printk(KERN_WARNING + "mydev: 24-bit DMA addressing not available.\n"); + goto ignore_this_device; + } + +When dma_set_mask() is successful, and returns zero, the kernel saves +away this mask you have provided. The kernel will use this +information later when you make DMA mappings. + +There is a case which we are aware of at this time, which is worth +mentioning in this documentation. If your device supports multiple +functions (for example a sound card provides playback and record +functions) and the various different functions have _different_ +DMA addressing limitations, you may wish to probe each mask and +only provide the functionality which the machine can handle. It +is important that the last call to dma_set_mask() be for the +most specific mask. + +Here is pseudo-code showing how this might be done: + + #define PLAYBACK_ADDRESS_BITS DMA_BIT_MASK(32) + #define RECORD_ADDRESS_BITS DMA_BIT_MASK(24) + + struct my_sound_card *card; + struct device *dev; + + ... + if (!dma_set_mask(dev, PLAYBACK_ADDRESS_BITS)) { + card->playback_enabled = 1; + } else { + card->playback_enabled = 0; + printk(KERN_WARNING "%s: Playback disabled due to DMA limitations.\n", + card->name); + } + if (!dma_set_mask(dev, RECORD_ADDRESS_BITS)) { + card->record_enabled = 1; + } else { + card->record_enabled = 0; + printk(KERN_WARNING "%s: Record disabled due to DMA limitations.\n", + card->name); + } + +A sound card was used as an example here because this genre of PCI +devices seems to be littered with ISA chips given a PCI front end, +and thus retaining the 16MB DMA addressing limitations of ISA. + + Types of DMA mappings + +There are two types of DMA mappings: + +- Consistent DMA mappings which are usually mapped at driver + initialization, unmapped at the end and for which the hardware should + guarantee that the device and the CPU can access the data + in parallel and will see updates made by each other without any + explicit software flushing. + + Think of "consistent" as "synchronous" or "coherent". + + The current default is to return consistent memory in the low 32 + bits of the bus space. However, for future compatibility you should + set the consistent mask even if this default is fine for your + driver. + + Good examples of what to use consistent mappings for are: + + - Network card DMA ring descriptors. + - SCSI adapter mailbox command data structures. + - Device firmware microcode executed out of + main memory. + + The invariant these examples all require is that any CPU store + to memory is immediately visible to the device, and vice + versa. Consistent mappings guarantee this. + + IMPORTANT: Consistent DMA memory does not preclude the usage of + proper memory barriers. The CPU may reorder stores to + consistent memory just as it may normal memory. Example: + if it is important for the device to see the first word + of a descriptor updated before the second, you must do + something like: + + desc->word0 = address; + wmb(); + desc->word1 = DESC_VALID; + + in order to get correct behavior on all platforms. + + Also, on some platforms your driver may need to flush CPU write + buffers in much the same way as it needs to flush write buffers + found in PCI bridges (such as by reading a register's value + after writing it). + +- Streaming DMA mappings which are usually mapped for one DMA + transfer, unmapped right after it (unless you use dma_sync_* below) + and for which hardware can optimize for sequential accesses. + + This of "streaming" as "asynchronous" or "outside the coherency + domain". + + Good examples of what to use streaming mappings for are: + + - Networking buffers transmitted/received by a device. + - Filesystem buffers written/read by a SCSI device. + + The interfaces for using this type of mapping were designed in + such a way that an implementation can make whatever performance + optimizations the hardware allows. To this end, when using + such mappings you must be explicit about what you want to happen. + +Neither type of DMA mapping has alignment restrictions that come from +the underlying bus, although some devices may have such restrictions. +Also, systems with caches that aren't DMA-coherent will work better +when the underlying buffers don't share cache lines with other data. + + + Using Consistent DMA mappings. + +To allocate and map large (PAGE_SIZE or so) consistent DMA regions, +you should do: + + dma_addr_t dma_handle; + + cpu_addr = dma_alloc_coherent(dev, size, &dma_handle, gfp); + +where device is a struct device *. This may be called in interrupt +context with the GFP_ATOMIC flag. + +Size is the length of the region you want to allocate, in bytes. + +This routine will allocate RAM for that region, so it acts similarly to +__get_free_pages (but takes size instead of a page order). If your +driver needs regions sized smaller than a page, you may prefer using +the dma_pool interface, described below. + +The consistent DMA mapping interfaces, for non-NULL dev, will by +default return a DMA address which is 32-bit addressable. Even if the +device indicates (via DMA mask) that it may address the upper 32-bits, +consistent allocation will only return > 32-bit addresses for DMA if +the consistent DMA mask has been explicitly changed via +dma_set_coherent_mask(). This is true of the dma_pool interface as +well. + +dma_alloc_coherent returns two values: the virtual address which you +can use to access it from the CPU and dma_handle which you pass to the +card. + +The cpu return address and the DMA bus master address are both +guaranteed to be aligned to the smallest PAGE_SIZE order which +is greater than or equal to the requested size. This invariant +exists (for example) to guarantee that if you allocate a chunk +which is smaller than or equal to 64 kilobytes, the extent of the +buffer you receive will not cross a 64K boundary. + +To unmap and free such a DMA region, you call: + + dma_free_coherent(dev, size, cpu_addr, dma_handle); + +where dev, size are the same as in the above call and cpu_addr and +dma_handle are the values dma_alloc_coherent returned to you. +This function may not be called in interrupt context. + +If your driver needs lots of smaller memory regions, you can write +custom code to subdivide pages returned by dma_alloc_coherent, +or you can use the dma_pool API to do that. A dma_pool is like +a kmem_cache, but it uses dma_alloc_coherent not __get_free_pages. +Also, it understands common hardware constraints for alignment, +like queue heads needing to be aligned on N byte boundaries. + +Create a dma_pool like this: + + struct dma_pool *pool; + + pool = dma_pool_create(name, dev, size, align, alloc); + +The "name" is for diagnostics (like a kmem_cache name); dev and size +are as above. The device's hardware alignment requirement for this +type of data is "align" (which is expressed in bytes, and must be a +power of two). If your device has no boundary crossing restrictions, +pass 0 for alloc; passing 4096 says memory allocated from this pool +must not cross 4KByte boundaries (but at that time it may be better to +go for dma_alloc_coherent directly instead). + +Allocate memory from a dma pool like this: + + cpu_addr = dma_pool_alloc(pool, flags, &dma_handle); + +flags are SLAB_KERNEL if blocking is permitted (not in_interrupt nor +holding SMP locks), SLAB_ATOMIC otherwise. Like dma_alloc_coherent, +this returns two values, cpu_addr and dma_handle. + +Free memory that was allocated from a dma_pool like this: + + dma_pool_free(pool, cpu_addr, dma_handle); + +where pool is what you passed to dma_pool_alloc, and cpu_addr and +dma_handle are the values dma_pool_alloc returned. This function +may be called in interrupt context. + +Destroy a dma_pool by calling: + + dma_pool_destroy(pool); + +Make sure you've called dma_pool_free for all memory allocated +from a pool before you destroy the pool. This function may not +be called in interrupt context. + + DMA Direction + +The interfaces described in subsequent portions of this document +take a DMA direction argument, which is an integer and takes on +one of the following values: + + DMA_BIDIRECTIONAL + DMA_TO_DEVICE + DMA_FROM_DEVICE + DMA_NONE + +One should provide the exact DMA direction if you know it. + +DMA_TO_DEVICE means "from main memory to the device" +DMA_FROM_DEVICE means "from the device to main memory" +It is the direction in which the data moves during the DMA +transfer. + +You are _strongly_ encouraged to specify this as precisely +as you possibly can. + +If you absolutely cannot know the direction of the DMA transfer, +specify DMA_BIDIRECTIONAL. It means that the DMA can go in +either direction. The platform guarantees that you may legally +specify this, and that it will work, but this may be at the +cost of performance for example. + +The value DMA_NONE is to be used for debugging. One can +hold this in a data structure before you come to know the +precise direction, and this will help catch cases where your +direction tracking logic has failed to set things up properly. + +Another advantage of specifying this value precisely (outside of +potential platform-specific optimizations of such) is for debugging. +Some platforms actually have a write permission boolean which DMA +mappings can be marked with, much like page protections in the user +program address space. Such platforms can and do report errors in the +kernel logs when the DMA controller hardware detects violation of the +permission setting. + +Only streaming mappings specify a direction, consistent mappings +implicitly have a direction attribute setting of +DMA_BIDIRECTIONAL. + +The SCSI subsystem tells you the direction to use in the +'sc_data_direction' member of the SCSI command your driver is +working on. + +For Networking drivers, it's a rather simple affair. For transmit +packets, map/unmap them with the DMA_TO_DEVICE direction +specifier. For receive packets, just the opposite, map/unmap them +with the DMA_FROM_DEVICE direction specifier. + + Using Streaming DMA mappings + +The streaming DMA mapping routines can be called from interrupt +context. There are two versions of each map/unmap, one which will +map/unmap a single memory region, and one which will map/unmap a +scatterlist. + +To map a single region, you do: + + struct device *dev = &my_dev->dev; + dma_addr_t dma_handle; + void *addr = buffer->ptr; + size_t size = buffer->len; + + dma_handle = dma_map_single(dev, addr, size, direction); + +and to unmap it: + + dma_unmap_single(dev, dma_handle, size, direction); + +You should call dma_unmap_single when the DMA activity is finished, e.g. +from the interrupt which told you that the DMA transfer is done. + +Using cpu pointers like this for single mappings has a disadvantage, +you cannot reference HIGHMEM memory in this way. Thus, there is a +map/unmap interface pair akin to dma_{map,unmap}_single. These +interfaces deal with page/offset pairs instead of cpu pointers. +Specifically: + + struct device *dev = &my_dev->dev; + dma_addr_t dma_handle; + struct page *page = buffer->page; + unsigned long offset = buffer->offset; + size_t size = buffer->len; + + dma_handle = dma_map_page(dev, page, offset, size, direction); + + ... + + dma_unmap_page(dev, dma_handle, size, direction); + +Here, "offset" means byte offset within the given page. + +With scatterlists, you map a region gathered from several regions by: + + int i, count = dma_map_sg(dev, sglist, nents, direction); + struct scatterlist *sg; + + for_each_sg(sglist, sg, count, i) { + hw_address[i] = sg_dma_address(sg); + hw_len[i] = sg_dma_len(sg); + } + +where nents is the number of entries in the sglist. + +The implementation is free to merge several consecutive sglist entries +into one (e.g. if DMA mapping is done with PAGE_SIZE granularity, any +consecutive sglist entries can be merged into one provided the first one +ends and the second one starts on a page boundary - in fact this is a huge +advantage for cards which either cannot do scatter-gather or have very +limited number of scatter-gather entries) and returns the actual number +of sg entries it mapped them to. On failure 0 is returned. + +Then you should loop count times (note: this can be less than nents times) +and use sg_dma_address() and sg_dma_len() macros where you previously +accessed sg->address and sg->length as shown above. + +To unmap a scatterlist, just call: + + dma_unmap_sg(dev, sglist, nents, direction); + +Again, make sure DMA activity has already finished. + +PLEASE NOTE: The 'nents' argument to the dma_unmap_sg call must be + the _same_ one you passed into the dma_map_sg call, + it should _NOT_ be the 'count' value _returned_ from the + dma_map_sg call. + +Every dma_map_{single,sg} call should have its dma_unmap_{single,sg} +counterpart, because the bus address space is a shared resource (although +in some ports the mapping is per each BUS so less devices contend for the +same bus address space) and you could render the machine unusable by eating +all bus addresses. + +If you need to use the same streaming DMA region multiple times and touch +the data in between the DMA transfers, the buffer needs to be synced +properly in order for the cpu and device to see the most uptodate and +correct copy of the DMA buffer. + +So, firstly, just map it with dma_map_{single,sg}, and after each DMA +transfer call either: + + dma_sync_single_for_cpu(dev, dma_handle, size, direction); + +or: + + dma_sync_sg_for_cpu(dev, sglist, nents, direction); + +as appropriate. + +Then, if you wish to let the device get at the DMA area again, +finish accessing the data with the cpu, and then before actually +giving the buffer to the hardware call either: + + dma_sync_single_for_device(dev, dma_handle, size, direction); + +or: + + dma_sync_sg_for_device(dev, sglist, nents, direction); + +as appropriate. + +After the last DMA transfer call one of the DMA unmap routines +dma_unmap_{single,sg}. If you don't touch the data from the first dma_map_* +call till dma_unmap_*, then you don't have to call the dma_sync_* +routines at all. + +Here is pseudo code which shows a situation in which you would need +to use the dma_sync_*() interfaces. + + my_card_setup_receive_buffer(struct my_card *cp, char *buffer, int len) + { + dma_addr_t mapping; + + mapping = dma_map_single(cp->dev, buffer, len, DMA_FROM_DEVICE); + + cp->rx_buf = buffer; + cp->rx_len = len; + cp->rx_dma = mapping; + + give_rx_buf_to_card(cp); + } + + ... + + my_card_interrupt_handler(int irq, void *devid, struct pt_regs *regs) + { + struct my_card *cp = devid; + + ... + if (read_card_status(cp) == RX_BUF_TRANSFERRED) { + struct my_card_header *hp; + + /* Examine the header to see if we wish + * to accept the data. But synchronize + * the DMA transfer with the CPU first + * so that we see updated contents. + */ + dma_sync_single_for_cpu(&cp->dev, cp->rx_dma, + cp->rx_len, + DMA_FROM_DEVICE); + + /* Now it is safe to examine the buffer. */ + hp = (struct my_card_header *) cp->rx_buf; + if (header_is_ok(hp)) { + dma_unmap_single(&cp->dev, cp->rx_dma, cp->rx_len, + DMA_FROM_DEVICE); + pass_to_upper_layers(cp->rx_buf); + make_and_setup_new_rx_buf(cp); + } else { + /* Just sync the buffer and give it back + * to the card. + */ + dma_sync_single_for_device(&cp->dev, + cp->rx_dma, + cp->rx_len, + DMA_FROM_DEVICE); + give_rx_buf_to_card(cp); + } + } + } + +Drivers converted fully to this interface should not use virt_to_bus any +longer, nor should they use bus_to_virt. Some drivers have to be changed a +little bit, because there is no longer an equivalent to bus_to_virt in the +dynamic DMA mapping scheme - you have to always store the DMA addresses +returned by the dma_alloc_coherent, dma_pool_alloc, and dma_map_single +calls (dma_map_sg stores them in the scatterlist itself if the platform +supports dynamic DMA mapping in hardware) in your driver structures and/or +in the card registers. + +All drivers should be using these interfaces with no exceptions. It +is planned to completely remove virt_to_bus() and bus_to_virt() as +they are entirely deprecated. Some ports already do not provide these +as it is impossible to correctly support them. + + Optimizing Unmap State Space Consumption + +On many platforms, dma_unmap_{single,page}() is simply a nop. +Therefore, keeping track of the mapping address and length is a waste +of space. Instead of filling your drivers up with ifdefs and the like +to "work around" this (which would defeat the whole purpose of a +portable API) the following facilities are provided. + +Actually, instead of describing the macros one by one, we'll +transform some example code. + +1) Use DEFINE_DMA_UNMAP_{ADDR,LEN} in state saving structures. + Example, before: + + struct ring_state { + struct sk_buff *skb; + dma_addr_t mapping; + __u32 len; + }; + + after: + + struct ring_state { + struct sk_buff *skb; + DEFINE_DMA_UNMAP_ADDR(mapping); + DEFINE_DMA_UNMAP_LEN(len); + }; + +2) Use dma_unmap_{addr,len}_set to set these values. + Example, before: + + ringp->mapping = FOO; + ringp->len = BAR; + + after: + + dma_unmap_addr_set(ringp, mapping, FOO); + dma_unmap_len_set(ringp, len, BAR); + +3) Use dma_unmap_{addr,len} to access these values. + Example, before: + + dma_unmap_single(dev, ringp->mapping, ringp->len, + DMA_FROM_DEVICE); + + after: + + dma_unmap_single(dev, + dma_unmap_addr(ringp, mapping), + dma_unmap_len(ringp, len), + DMA_FROM_DEVICE); + +It really should be self-explanatory. We treat the ADDR and LEN +separately, because it is possible for an implementation to only +need the address in order to perform the unmap operation. + + Platform Issues + +If you are just writing drivers for Linux and do not maintain +an architecture port for the kernel, you can safely skip down +to "Closing". + +1) Struct scatterlist requirements. + + Struct scatterlist must contain, at a minimum, the following + members: + + struct page *page; + unsigned int offset; + unsigned int length; + + The base address is specified by a "page+offset" pair. + + Previous versions of struct scatterlist contained a "void *address" + field that was sometimes used instead of page+offset. As of Linux + 2.5., page+offset is always used, and the "address" field has been + deleted. + +2) More to come... + + Handling Errors + +DMA address space is limited on some architectures and an allocation +failure can be determined by: + +- checking if dma_alloc_coherent returns NULL or dma_map_sg returns 0 + +- checking the returned dma_addr_t of dma_map_single and dma_map_page + by using dma_mapping_error(): + + dma_addr_t dma_handle; + + dma_handle = dma_map_single(dev, addr, size, direction); + if (dma_mapping_error(dev, dma_handle)) { + /* + * reduce current DMA mapping usage, + * delay and try again later or + * reset driver. + */ + } + + Closing + +This document, and the API itself, would not be in it's current +form without the feedback and suggestions from numerous individuals. +We would like to specifically mention, in no particular order, the +following people: + + Russell King + Leo Dagum + Ralf Baechle + Grant Grundler + Jay Estabrook + Thomas Sailer + Andrea Arcangeli + Jens Axboe + David Mosberger-Tang diff --git a/Documentation/PCI/PCI-DMA-mapping.txt b/Documentation/PCI/PCI-DMA-mapping.txt deleted file mode 100644 index 52618ab069ad..000000000000 --- a/Documentation/PCI/PCI-DMA-mapping.txt +++ /dev/null @@ -1,758 +0,0 @@ - Dynamic DMA mapping Guide - ========================= - - David S. Miller - Richard Henderson - Jakub Jelinek - -This is a guide to device driver writers on how to use the DMA API -with example pseudo-code. For a concise description of the API, see -DMA-API.txt. - -Most of the 64bit platforms have special hardware that translates bus -addresses (DMA addresses) into physical addresses. This is similar to -how page tables and/or a TLB translates virtual addresses to physical -addresses on a CPU. This is needed so that e.g. PCI devices can -access with a Single Address Cycle (32bit DMA address) any page in the -64bit physical address space. Previously in Linux those 64bit -platforms had to set artificial limits on the maximum RAM size in the -system, so that the virt_to_bus() static scheme works (the DMA address -translation tables were simply filled on bootup to map each bus -address to the physical page __pa(bus_to_virt())). - -So that Linux can use the dynamic DMA mapping, it needs some help from the -drivers, namely it has to take into account that DMA addresses should be -mapped only for the time they are actually used and unmapped after the DMA -transfer. - -The following API will work of course even on platforms where no such -hardware exists. - -Note that the DMA API works with any bus independent of the underlying -microprocessor architecture. You should use the DMA API rather than -the bus specific DMA API (e.g. pci_dma_*). - -First of all, you should make sure - -#include - -is in your driver. This file will obtain for you the definition of the -dma_addr_t (which can hold any valid DMA address for the platform) -type which should be used everywhere you hold a DMA (bus) address -returned from the DMA mapping functions. - - What memory is DMA'able? - -The first piece of information you must know is what kernel memory can -be used with the DMA mapping facilities. There has been an unwritten -set of rules regarding this, and this text is an attempt to finally -write them down. - -If you acquired your memory via the page allocator -(i.e. __get_free_page*()) or the generic memory allocators -(i.e. kmalloc() or kmem_cache_alloc()) then you may DMA to/from -that memory using the addresses returned from those routines. - -This means specifically that you may _not_ use the memory/addresses -returned from vmalloc() for DMA. It is possible to DMA to the -_underlying_ memory mapped into a vmalloc() area, but this requires -walking page tables to get the physical addresses, and then -translating each of those pages back to a kernel address using -something like __va(). [ EDIT: Update this when we integrate -Gerd Knorr's generic code which does this. ] - -This rule also means that you may use neither kernel image addresses -(items in data/text/bss segments), nor module image addresses, nor -stack addresses for DMA. These could all be mapped somewhere entirely -different than the rest of physical memory. Even if those classes of -memory could physically work with DMA, you'd need to ensure the I/O -buffers were cacheline-aligned. Without that, you'd see cacheline -sharing problems (data corruption) on CPUs with DMA-incoherent caches. -(The CPU could write to one word, DMA would write to a different one -in the same cache line, and one of them could be overwritten.) - -Also, this means that you cannot take the return of a kmap() -call and DMA to/from that. This is similar to vmalloc(). - -What about block I/O and networking buffers? The block I/O and -networking subsystems make sure that the buffers they use are valid -for you to DMA from/to. - - DMA addressing limitations - -Does your device have any DMA addressing limitations? For example, is -your device only capable of driving the low order 24-bits of address? -If so, you need to inform the kernel of this fact. - -By default, the kernel assumes that your device can address the full -32-bits. For a 64-bit capable device, this needs to be increased. -And for a device with limitations, as discussed in the previous -paragraph, it needs to be decreased. - -Special note about PCI: PCI-X specification requires PCI-X devices to -support 64-bit addressing (DAC) for all transactions. And at least -one platform (SGI SN2) requires 64-bit consistent allocations to -operate correctly when the IO bus is in PCI-X mode. - -For correct operation, you must interrogate the kernel in your device -probe routine to see if the DMA controller on the machine can properly -support the DMA addressing limitation your device has. It is good -style to do this even if your device holds the default setting, -because this shows that you did think about these issues wrt. your -device. - -The query is performed via a call to dma_set_mask(): - - int dma_set_mask(struct device *dev, u64 mask); - -The query for consistent allocations is performed via a call to -dma_set_coherent_mask(): - - int dma_set_coherent_mask(struct device *dev, u64 mask); - -Here, dev is a pointer to the device struct of your device, and mask -is a bit mask describing which bits of an address your device -supports. It returns zero if your card can perform DMA properly on -the machine given the address mask you provided. In general, the -device struct of your device is embedded in the bus specific device -struct of your device. For example, a pointer to the device struct of -your PCI device is pdev->dev (pdev is a pointer to the PCI device -struct of your device). - -If it returns non-zero, your device cannot perform DMA properly on -this platform, and attempting to do so will result in undefined -behavior. You must either use a different mask, or not use DMA. - -This means that in the failure case, you have three options: - -1) Use another DMA mask, if possible (see below). -2) Use some non-DMA mode for data transfer, if possible. -3) Ignore this device and do not initialize it. - -It is recommended that your driver print a kernel KERN_WARNING message -when you end up performing either #2 or #3. In this manner, if a user -of your driver reports that performance is bad or that the device is not -even detected, you can ask them for the kernel messages to find out -exactly why. - -The standard 32-bit addressing device would do something like this: - - if (dma_set_mask(dev, DMA_BIT_MASK(32))) { - printk(KERN_WARNING - "mydev: No suitable DMA available.\n"); - goto ignore_this_device; - } - -Another common scenario is a 64-bit capable device. The approach here -is to try for 64-bit addressing, but back down to a 32-bit mask that -should not fail. The kernel may fail the 64-bit mask not because the -platform is not capable of 64-bit addressing. Rather, it may fail in -this case simply because 32-bit addressing is done more efficiently -than 64-bit addressing. For example, Sparc64 PCI SAC addressing is -more efficient than DAC addressing. - -Here is how you would handle a 64-bit capable device which can drive -all 64-bits when accessing streaming DMA: - - int using_dac; - - if (!dma_set_mask(dev, DMA_BIT_MASK(64))) { - using_dac = 1; - } else if (!dma_set_mask(dev, DMA_BIT_MASK(32))) { - using_dac = 0; - } else { - printk(KERN_WARNING - "mydev: No suitable DMA available.\n"); - goto ignore_this_device; - } - -If a card is capable of using 64-bit consistent allocations as well, -the case would look like this: - - int using_dac, consistent_using_dac; - - if (!dma_set_mask(dev, DMA_BIT_MASK(64))) { - using_dac = 1; - consistent_using_dac = 1; - dma_set_coherent_mask(dev, DMA_BIT_MASK(64)); - } else if (!dma_set_mask(dev, DMA_BIT_MASK(32))) { - using_dac = 0; - consistent_using_dac = 0; - dma_set_coherent_mask(dev, DMA_BIT_MASK(32)); - } else { - printk(KERN_WARNING - "mydev: No suitable DMA available.\n"); - goto ignore_this_device; - } - -dma_set_coherent_mask() will always be able to set the same or a -smaller mask as dma_set_mask(). However for the rare case that a -device driver only uses consistent allocations, one would have to -check the return value from dma_set_coherent_mask(). - -Finally, if your device can only drive the low 24-bits of -address you might do something like: - - if (dma_set_mask(dev, DMA_BIT_MASK(24))) { - printk(KERN_WARNING - "mydev: 24-bit DMA addressing not available.\n"); - goto ignore_this_device; - } - -When dma_set_mask() is successful, and returns zero, the kernel saves -away this mask you have provided. The kernel will use this -information later when you make DMA mappings. - -There is a case which we are aware of at this time, which is worth -mentioning in this documentation. If your device supports multiple -functions (for example a sound card provides playback and record -functions) and the various different functions have _different_ -DMA addressing limitations, you may wish to probe each mask and -only provide the functionality which the machine can handle. It -is important that the last call to dma_set_mask() be for the -most specific mask. - -Here is pseudo-code showing how this might be done: - - #define PLAYBACK_ADDRESS_BITS DMA_BIT_MASK(32) - #define RECORD_ADDRESS_BITS DMA_BIT_MASK(24) - - struct my_sound_card *card; - struct device *dev; - - ... - if (!dma_set_mask(dev, PLAYBACK_ADDRESS_BITS)) { - card->playback_enabled = 1; - } else { - card->playback_enabled = 0; - printk(KERN_WARNING "%s: Playback disabled due to DMA limitations.\n", - card->name); - } - if (!dma_set_mask(dev, RECORD_ADDRESS_BITS)) { - card->record_enabled = 1; - } else { - card->record_enabled = 0; - printk(KERN_WARNING "%s: Record disabled due to DMA limitations.\n", - card->name); - } - -A sound card was used as an example here because this genre of PCI -devices seems to be littered with ISA chips given a PCI front end, -and thus retaining the 16MB DMA addressing limitations of ISA. - - Types of DMA mappings - -There are two types of DMA mappings: - -- Consistent DMA mappings which are usually mapped at driver - initialization, unmapped at the end and for which the hardware should - guarantee that the device and the CPU can access the data - in parallel and will see updates made by each other without any - explicit software flushing. - - Think of "consistent" as "synchronous" or "coherent". - - The current default is to return consistent memory in the low 32 - bits of the bus space. However, for future compatibility you should - set the consistent mask even if this default is fine for your - driver. - - Good examples of what to use consistent mappings for are: - - - Network card DMA ring descriptors. - - SCSI adapter mailbox command data structures. - - Device firmware microcode executed out of - main memory. - - The invariant these examples all require is that any CPU store - to memory is immediately visible to the device, and vice - versa. Consistent mappings guarantee this. - - IMPORTANT: Consistent DMA memory does not preclude the usage of - proper memory barriers. The CPU may reorder stores to - consistent memory just as it may normal memory. Example: - if it is important for the device to see the first word - of a descriptor updated before the second, you must do - something like: - - desc->word0 = address; - wmb(); - desc->word1 = DESC_VALID; - - in order to get correct behavior on all platforms. - - Also, on some platforms your driver may need to flush CPU write - buffers in much the same way as it needs to flush write buffers - found in PCI bridges (such as by reading a register's value - after writing it). - -- Streaming DMA mappings which are usually mapped for one DMA - transfer, unmapped right after it (unless you use dma_sync_* below) - and for which hardware can optimize for sequential accesses. - - This of "streaming" as "asynchronous" or "outside the coherency - domain". - - Good examples of what to use streaming mappings for are: - - - Networking buffers transmitted/received by a device. - - Filesystem buffers written/read by a SCSI device. - - The interfaces for using this type of mapping were designed in - such a way that an implementation can make whatever performance - optimizations the hardware allows. To this end, when using - such mappings you must be explicit about what you want to happen. - -Neither type of DMA mapping has alignment restrictions that come from -the underlying bus, although some devices may have such restrictions. -Also, systems with caches that aren't DMA-coherent will work better -when the underlying buffers don't share cache lines with other data. - - - Using Consistent DMA mappings. - -To allocate and map large (PAGE_SIZE or so) consistent DMA regions, -you should do: - - dma_addr_t dma_handle; - - cpu_addr = dma_alloc_coherent(dev, size, &dma_handle, gfp); - -where device is a struct device *. This may be called in interrupt -context with the GFP_ATOMIC flag. - -Size is the length of the region you want to allocate, in bytes. - -This routine will allocate RAM for that region, so it acts similarly to -__get_free_pages (but takes size instead of a page order). If your -driver needs regions sized smaller than a page, you may prefer using -the dma_pool interface, described below. - -The consistent DMA mapping interfaces, for non-NULL dev, will by -default return a DMA address which is 32-bit addressable. Even if the -device indicates (via DMA mask) that it may address the upper 32-bits, -consistent allocation will only return > 32-bit addresses for DMA if -the consistent DMA mask has been explicitly changed via -dma_set_coherent_mask(). This is true of the dma_pool interface as -well. - -dma_alloc_coherent returns two values: the virtual address which you -can use to access it from the CPU and dma_handle which you pass to the -card. - -The cpu return address and the DMA bus master address are both -guaranteed to be aligned to the smallest PAGE_SIZE order which -is greater than or equal to the requested size. This invariant -exists (for example) to guarantee that if you allocate a chunk -which is smaller than or equal to 64 kilobytes, the extent of the -buffer you receive will not cross a 64K boundary. - -To unmap and free such a DMA region, you call: - - dma_free_coherent(dev, size, cpu_addr, dma_handle); - -where dev, size are the same as in the above call and cpu_addr and -dma_handle are the values dma_alloc_coherent returned to you. -This function may not be called in interrupt context. - -If your driver needs lots of smaller memory regions, you can write -custom code to subdivide pages returned by dma_alloc_coherent, -or you can use the dma_pool API to do that. A dma_pool is like -a kmem_cache, but it uses dma_alloc_coherent not __get_free_pages. -Also, it understands common hardware constraints for alignment, -like queue heads needing to be aligned on N byte boundaries. - -Create a dma_pool like this: - - struct dma_pool *pool; - - pool = dma_pool_create(name, dev, size, align, alloc); - -The "name" is for diagnostics (like a kmem_cache name); dev and size -are as above. The device's hardware alignment requirement for this -type of data is "align" (which is expressed in bytes, and must be a -power of two). If your device has no boundary crossing restrictions, -pass 0 for alloc; passing 4096 says memory allocated from this pool -must not cross 4KByte boundaries (but at that time it may be better to -go for dma_alloc_coherent directly instead). - -Allocate memory from a dma pool like this: - - cpu_addr = dma_pool_alloc(pool, flags, &dma_handle); - -flags are SLAB_KERNEL if blocking is permitted (not in_interrupt nor -holding SMP locks), SLAB_ATOMIC otherwise. Like dma_alloc_coherent, -this returns two values, cpu_addr and dma_handle. - -Free memory that was allocated from a dma_pool like this: - - dma_pool_free(pool, cpu_addr, dma_handle); - -where pool is what you passed to dma_pool_alloc, and cpu_addr and -dma_handle are the values dma_pool_alloc returned. This function -may be called in interrupt context. - -Destroy a dma_pool by calling: - - dma_pool_destroy(pool); - -Make sure you've called dma_pool_free for all memory allocated -from a pool before you destroy the pool. This function may not -be called in interrupt context. - - DMA Direction - -The interfaces described in subsequent portions of this document -take a DMA direction argument, which is an integer and takes on -one of the following values: - - DMA_BIDIRECTIONAL - DMA_TO_DEVICE - DMA_FROM_DEVICE - DMA_NONE - -One should provide the exact DMA direction if you know it. - -DMA_TO_DEVICE means "from main memory to the device" -DMA_FROM_DEVICE means "from the device to main memory" -It is the direction in which the data moves during the DMA -transfer. - -You are _strongly_ encouraged to specify this as precisely -as you possibly can. - -If you absolutely cannot know the direction of the DMA transfer, -specify DMA_BIDIRECTIONAL. It means that the DMA can go in -either direction. The platform guarantees that you may legally -specify this, and that it will work, but this may be at the -cost of performance for example. - -The value DMA_NONE is to be used for debugging. One can -hold this in a data structure before you come to know the -precise direction, and this will help catch cases where your -direction tracking logic has failed to set things up properly. - -Another advantage of specifying this value precisely (outside of -potential platform-specific optimizations of such) is for debugging. -Some platforms actually have a write permission boolean which DMA -mappings can be marked with, much like page protections in the user -program address space. Such platforms can and do report errors in the -kernel logs when the DMA controller hardware detects violation of the -permission setting. - -Only streaming mappings specify a direction, consistent mappings -implicitly have a direction attribute setting of -DMA_BIDIRECTIONAL. - -The SCSI subsystem tells you the direction to use in the -'sc_data_direction' member of the SCSI command your driver is -working on. - -For Networking drivers, it's a rather simple affair. For transmit -packets, map/unmap them with the DMA_TO_DEVICE direction -specifier. For receive packets, just the opposite, map/unmap them -with the DMA_FROM_DEVICE direction specifier. - - Using Streaming DMA mappings - -The streaming DMA mapping routines can be called from interrupt -context. There are two versions of each map/unmap, one which will -map/unmap a single memory region, and one which will map/unmap a -scatterlist. - -To map a single region, you do: - - struct device *dev = &my_dev->dev; - dma_addr_t dma_handle; - void *addr = buffer->ptr; - size_t size = buffer->len; - - dma_handle = dma_map_single(dev, addr, size, direction); - -and to unmap it: - - dma_unmap_single(dev, dma_handle, size, direction); - -You should call dma_unmap_single when the DMA activity is finished, e.g. -from the interrupt which told you that the DMA transfer is done. - -Using cpu pointers like this for single mappings has a disadvantage, -you cannot reference HIGHMEM memory in this way. Thus, there is a -map/unmap interface pair akin to dma_{map,unmap}_single. These -interfaces deal with page/offset pairs instead of cpu pointers. -Specifically: - - struct device *dev = &my_dev->dev; - dma_addr_t dma_handle; - struct page *page = buffer->page; - unsigned long offset = buffer->offset; - size_t size = buffer->len; - - dma_handle = dma_map_page(dev, page, offset, size, direction); - - ... - - dma_unmap_page(dev, dma_handle, size, direction); - -Here, "offset" means byte offset within the given page. - -With scatterlists, you map a region gathered from several regions by: - - int i, count = dma_map_sg(dev, sglist, nents, direction); - struct scatterlist *sg; - - for_each_sg(sglist, sg, count, i) { - hw_address[i] = sg_dma_address(sg); - hw_len[i] = sg_dma_len(sg); - } - -where nents is the number of entries in the sglist. - -The implementation is free to merge several consecutive sglist entries -into one (e.g. if DMA mapping is done with PAGE_SIZE granularity, any -consecutive sglist entries can be merged into one provided the first one -ends and the second one starts on a page boundary - in fact this is a huge -advantage for cards which either cannot do scatter-gather or have very -limited number of scatter-gather entries) and returns the actual number -of sg entries it mapped them to. On failure 0 is returned. - -Then you should loop count times (note: this can be less than nents times) -and use sg_dma_address() and sg_dma_len() macros where you previously -accessed sg->address and sg->length as shown above. - -To unmap a scatterlist, just call: - - dma_unmap_sg(dev, sglist, nents, direction); - -Again, make sure DMA activity has already finished. - -PLEASE NOTE: The 'nents' argument to the dma_unmap_sg call must be - the _same_ one you passed into the dma_map_sg call, - it should _NOT_ be the 'count' value _returned_ from the - dma_map_sg call. - -Every dma_map_{single,sg} call should have its dma_unmap_{single,sg} -counterpart, because the bus address space is a shared resource (although -in some ports the mapping is per each BUS so less devices contend for the -same bus address space) and you could render the machine unusable by eating -all bus addresses. - -If you need to use the same streaming DMA region multiple times and touch -the data in between the DMA transfers, the buffer needs to be synced -properly in order for the cpu and device to see the most uptodate and -correct copy of the DMA buffer. - -So, firstly, just map it with dma_map_{single,sg}, and after each DMA -transfer call either: - - dma_sync_single_for_cpu(dev, dma_handle, size, direction); - -or: - - dma_sync_sg_for_cpu(dev, sglist, nents, direction); - -as appropriate. - -Then, if you wish to let the device get at the DMA area again, -finish accessing the data with the cpu, and then before actually -giving the buffer to the hardware call either: - - dma_sync_single_for_device(dev, dma_handle, size, direction); - -or: - - dma_sync_sg_for_device(dev, sglist, nents, direction); - -as appropriate. - -After the last DMA transfer call one of the DMA unmap routines -dma_unmap_{single,sg}. If you don't touch the data from the first dma_map_* -call till dma_unmap_*, then you don't have to call the dma_sync_* -routines at all. - -Here is pseudo code which shows a situation in which you would need -to use the dma_sync_*() interfaces. - - my_card_setup_receive_buffer(struct my_card *cp, char *buffer, int len) - { - dma_addr_t mapping; - - mapping = dma_map_single(cp->dev, buffer, len, DMA_FROM_DEVICE); - - cp->rx_buf = buffer; - cp->rx_len = len; - cp->rx_dma = mapping; - - give_rx_buf_to_card(cp); - } - - ... - - my_card_interrupt_handler(int irq, void *devid, struct pt_regs *regs) - { - struct my_card *cp = devid; - - ... - if (read_card_status(cp) == RX_BUF_TRANSFERRED) { - struct my_card_header *hp; - - /* Examine the header to see if we wish - * to accept the data. But synchronize - * the DMA transfer with the CPU first - * so that we see updated contents. - */ - dma_sync_single_for_cpu(&cp->dev, cp->rx_dma, - cp->rx_len, - DMA_FROM_DEVICE); - - /* Now it is safe to examine the buffer. */ - hp = (struct my_card_header *) cp->rx_buf; - if (header_is_ok(hp)) { - dma_unmap_single(&cp->dev, cp->rx_dma, cp->rx_len, - DMA_FROM_DEVICE); - pass_to_upper_layers(cp->rx_buf); - make_and_setup_new_rx_buf(cp); - } else { - /* Just sync the buffer and give it back - * to the card. - */ - dma_sync_single_for_device(&cp->dev, - cp->rx_dma, - cp->rx_len, - DMA_FROM_DEVICE); - give_rx_buf_to_card(cp); - } - } - } - -Drivers converted fully to this interface should not use virt_to_bus any -longer, nor should they use bus_to_virt. Some drivers have to be changed a -little bit, because there is no longer an equivalent to bus_to_virt in the -dynamic DMA mapping scheme - you have to always store the DMA addresses -returned by the dma_alloc_coherent, dma_pool_alloc, and dma_map_single -calls (dma_map_sg stores them in the scatterlist itself if the platform -supports dynamic DMA mapping in hardware) in your driver structures and/or -in the card registers. - -All drivers should be using these interfaces with no exceptions. It -is planned to completely remove virt_to_bus() and bus_to_virt() as -they are entirely deprecated. Some ports already do not provide these -as it is impossible to correctly support them. - - Optimizing Unmap State Space Consumption - -On many platforms, dma_unmap_{single,page}() is simply a nop. -Therefore, keeping track of the mapping address and length is a waste -of space. Instead of filling your drivers up with ifdefs and the like -to "work around" this (which would defeat the whole purpose of a -portable API) the following facilities are provided. - -Actually, instead of describing the macros one by one, we'll -transform some example code. - -1) Use DEFINE_DMA_UNMAP_{ADDR,LEN} in state saving structures. - Example, before: - - struct ring_state { - struct sk_buff *skb; - dma_addr_t mapping; - __u32 len; - }; - - after: - - struct ring_state { - struct sk_buff *skb; - DEFINE_DMA_UNMAP_ADDR(mapping); - DEFINE_DMA_UNMAP_LEN(len); - }; - -2) Use dma_unmap_{addr,len}_set to set these values. - Example, before: - - ringp->mapping = FOO; - ringp->len = BAR; - - after: - - dma_unmap_addr_set(ringp, mapping, FOO); - dma_unmap_len_set(ringp, len, BAR); - -3) Use dma_unmap_{addr,len} to access these values. - Example, before: - - dma_unmap_single(dev, ringp->mapping, ringp->len, - DMA_FROM_DEVICE); - - after: - - dma_unmap_single(dev, - dma_unmap_addr(ringp, mapping), - dma_unmap_len(ringp, len), - DMA_FROM_DEVICE); - -It really should be self-explanatory. We treat the ADDR and LEN -separately, because it is possible for an implementation to only -need the address in order to perform the unmap operation. - - Platform Issues - -If you are just writing drivers for Linux and do not maintain -an architecture port for the kernel, you can safely skip down -to "Closing". - -1) Struct scatterlist requirements. - - Struct scatterlist must contain, at a minimum, the following - members: - - struct page *page; - unsigned int offset; - unsigned int length; - - The base address is specified by a "page+offset" pair. - - Previous versions of struct scatterlist contained a "void *address" - field that was sometimes used instead of page+offset. As of Linux - 2.5., page+offset is always used, and the "address" field has been - deleted. - -2) More to come... - - Handling Errors - -DMA address space is limited on some architectures and an allocation -failure can be determined by: - -- checking if dma_alloc_coherent returns NULL or dma_map_sg returns 0 - -- checking the returned dma_addr_t of dma_map_single and dma_map_page - by using dma_mapping_error(): - - dma_addr_t dma_handle; - - dma_handle = dma_map_single(dev, addr, size, direction); - if (dma_mapping_error(dev, dma_handle)) { - /* - * reduce current DMA mapping usage, - * delay and try again later or - * reset driver. - */ - } - - Closing - -This document, and the API itself, would not be in it's current -form without the feedback and suggestions from numerous individuals. -We would like to specifically mention, in no particular order, the -following people: - - Russell King - Leo Dagum - Ralf Baechle - Grant Grundler - Jay Estabrook - Thomas Sailer - Andrea Arcangeli - Jens Axboe - David Mosberger-Tang -- cgit v1.2.3 From a33f32244d8550da8b4a26e277ce07d5c6d158b5 Mon Sep 17 00:00:00 2001 From: Francis Galiegue Date: Fri, 23 Apr 2010 00:08:02 +0200 Subject: Documentation/: it's -> its where appropriate Fix obvious cases of "it's" being used when "its" was meant. Signed-off-by: Francis Galiegue Acked-by: Randy Dunlap Signed-off-by: Jiri Kosina --- Documentation/ABI/testing/sysfs-devices-memory | 2 +- Documentation/DMA-API-HOWTO.txt | 2 +- Documentation/DocBook/libata.tmpl | 2 +- Documentation/PCI/pci-error-recovery.txt | 4 ++-- Documentation/Smack.txt | 2 +- Documentation/arm/SA1100/ADSBitsy | 2 +- Documentation/arm/Sharp-LH/ADC-LH7-Touchscreen | 2 +- Documentation/atomic_ops.txt | 2 +- Documentation/blackfin/bfin-gpio-notes.txt | 2 +- Documentation/cachetlb.txt | 6 +++--- Documentation/cgroups/memcg_test.txt | 2 +- Documentation/cgroups/memory.txt | 2 +- Documentation/connector/connector.txt | 2 +- Documentation/dvb/ci.txt | 2 +- Documentation/dvb/contributors.txt | 2 +- Documentation/filesystems/autofs4-mount-control.txt | 2 +- Documentation/filesystems/ceph.txt | 2 +- Documentation/filesystems/dlmfs.txt | 2 +- Documentation/filesystems/fiemap.txt | 12 ++++++------ Documentation/filesystems/fuse.txt | 4 ++-- Documentation/filesystems/hpfs.txt | 2 +- Documentation/filesystems/nfs/rpc-cache.txt | 2 +- Documentation/filesystems/proc.txt | 4 ++-- Documentation/filesystems/smbfs.txt | 2 +- Documentation/filesystems/vfs.txt | 2 +- Documentation/hwmon/lm85 | 2 +- Documentation/input/joystick.txt | 2 +- Documentation/intel_txt.txt | 2 +- Documentation/kbuild/kconfig-language.txt | 2 +- Documentation/kernel-docs.txt | 10 +++++----- Documentation/kprobes.txt | 2 +- Documentation/laptops/laptop-mode.txt | 2 +- Documentation/lguest/lguest.c | 2 +- Documentation/md.txt | 2 +- Documentation/netlabel/lsm_interface.txt | 2 +- Documentation/networking/ifenslave.c | 2 +- Documentation/networking/packet_mmap.txt | 4 ++-- Documentation/power/regulator/consumer.txt | 10 +++++----- Documentation/power/regulator/machine.txt | 2 +- Documentation/power/regulator/overview.txt | 6 +++--- Documentation/powerpc/booting-without-of.txt | 2 +- Documentation/powerpc/phyp-assisted-dump.txt | 2 +- Documentation/rt-mutex-design.txt | 2 +- Documentation/scsi/ChangeLog.lpfc | 4 ++-- Documentation/scsi/FlashPoint.txt | 2 +- Documentation/scsi/dtc3x80.txt | 2 +- Documentation/scsi/ncr53c8xx.txt | 2 +- Documentation/scsi/osst.txt | 2 +- Documentation/scsi/scsi_fc_transport.txt | 4 ++-- Documentation/scsi/sym53c8xx_2.txt | 2 +- Documentation/sound/alsa/soc/dapm.txt | 4 ++-- Documentation/sound/alsa/soc/machine.txt | 2 +- Documentation/sound/alsa/soc/overview.txt | 2 +- Documentation/usb/WUSB-Design-overview.txt | 2 +- Documentation/vm/numa_memory_policy.txt | 4 ++-- Documentation/w1/w1.generic | 2 +- 56 files changed, 81 insertions(+), 81 deletions(-) (limited to 'Documentation/PCI') diff --git a/Documentation/ABI/testing/sysfs-devices-memory b/Documentation/ABI/testing/sysfs-devices-memory index bf1627b02a03..aba7d989208c 100644 --- a/Documentation/ABI/testing/sysfs-devices-memory +++ b/Documentation/ABI/testing/sysfs-devices-memory @@ -43,7 +43,7 @@ Date: September 2008 Contact: Badari Pulavarty Description: The file /sys/devices/system/memory/memoryX/state - is read-write. When read, it's contents show the + is read-write. When read, its contents show the online/offline state of the memory section. When written, root can toggle the the online/offline state of a removable memory section (see removable file description above) diff --git a/Documentation/DMA-API-HOWTO.txt b/Documentation/DMA-API-HOWTO.txt index 52618ab069ad..2e435adfbd6b 100644 --- a/Documentation/DMA-API-HOWTO.txt +++ b/Documentation/DMA-API-HOWTO.txt @@ -742,7 +742,7 @@ failure can be determined by: Closing -This document, and the API itself, would not be in it's current +This document, and the API itself, would not be in its current form without the feedback and suggestions from numerous individuals. We would like to specifically mention, in no particular order, the following people: diff --git a/Documentation/DocBook/libata.tmpl b/Documentation/DocBook/libata.tmpl index ba9975771503..261b57bc6f08 100644 --- a/Documentation/DocBook/libata.tmpl +++ b/Documentation/DocBook/libata.tmpl @@ -490,7 +490,7 @@ void (*host_stop) (struct ata_host_set *host_set); allocates space for a legacy IDE PRD table and returns. - ->port_stop() is called after ->host_stop(). It's sole function + ->port_stop() is called after ->host_stop(). Its sole function is to release DMA/memory resources, now that they are no longer actively being used. Many drivers also free driver-private data from port at this time. diff --git a/Documentation/PCI/pci-error-recovery.txt b/Documentation/PCI/pci-error-recovery.txt index e83f2ea76415..898ded24510d 100644 --- a/Documentation/PCI/pci-error-recovery.txt +++ b/Documentation/PCI/pci-error-recovery.txt @@ -216,7 +216,7 @@ The driver should return one of the following result codes: - PCI_ERS_RESULT_NEED_RESET Driver returns this if it thinks the device is not - recoverable in it's current state and it needs a slot + recoverable in its current state and it needs a slot reset to proceed. - PCI_ERS_RESULT_DISCONNECT @@ -241,7 +241,7 @@ in working condition. The driver is not supposed to restart normal driver I/O operations at this point. It should limit itself to "probing" the device to -check it's recoverability status. If all is right, then the platform +check its recoverability status. If all is right, then the platform will call resume() once all drivers have ack'd link_reset(). Result codes: diff --git a/Documentation/Smack.txt b/Documentation/Smack.txt index 34614b4c708e..e9dab41c0fe0 100644 --- a/Documentation/Smack.txt +++ b/Documentation/Smack.txt @@ -73,7 +73,7 @@ NOTE: Smack labels are limited to 23 characters. The attr command If you don't do anything special all users will get the floor ("_") label when they log in. If you do want to log in via the hacked ssh at other labels use the attr command to set the smack value on the -home directory and it's contents. +home directory and its contents. You can add access rules in /etc/smack/accesses. They take the form: diff --git a/Documentation/arm/SA1100/ADSBitsy b/Documentation/arm/SA1100/ADSBitsy index 7197a9e958ee..f9f62e8c0719 100644 --- a/Documentation/arm/SA1100/ADSBitsy +++ b/Documentation/arm/SA1100/ADSBitsy @@ -32,7 +32,7 @@ Notes: - The flash on board is divided into 3 partitions. You should be careful to use flash on board. - It's partition is different from GraphicsClient Plus and GraphicsMaster + Its partition is different from GraphicsClient Plus and GraphicsMaster - 16bpp mode requires a different cable than what ships with the board. Contact ADS or look through the manual to wire your own. Currently, diff --git a/Documentation/arm/Sharp-LH/ADC-LH7-Touchscreen b/Documentation/arm/Sharp-LH/ADC-LH7-Touchscreen index 1e6a23fdf2fc..dc460f055647 100644 --- a/Documentation/arm/Sharp-LH/ADC-LH7-Touchscreen +++ b/Documentation/arm/Sharp-LH/ADC-LH7-Touchscreen @@ -7,7 +7,7 @@ The driver only implements a four-wire touch panel protocol. The touchscreen driver is maintenance free except for the pen-down or touch threshold. Some resistive displays and board combinations may -require tuning of this threshold. The driver exposes some of it's +require tuning of this threshold. The driver exposes some of its internal state in the sys filesystem. If the kernel is configured with it, CONFIG_SYSFS, and sysfs is mounted at /sys, there will be a directory diff --git a/Documentation/atomic_ops.txt b/Documentation/atomic_ops.txt index 396bec3b74ed..ac4d47187122 100644 --- a/Documentation/atomic_ops.txt +++ b/Documentation/atomic_ops.txt @@ -320,7 +320,7 @@ counter decrement would not become globally visible until the obj->active update does. As a historical note, 32-bit Sparc used to only allow usage of -24-bits of it's atomic_t type. This was because it used 8 bits +24-bits of its atomic_t type. This was because it used 8 bits as a spinlock for SMP safety. Sparc32 lacked a "compare and swap" type instruction. However, 32-bit Sparc has since been moved over to a "hash table of spinlocks" scheme, that allows the full 32-bit diff --git a/Documentation/blackfin/bfin-gpio-notes.txt b/Documentation/blackfin/bfin-gpio-notes.txt index 9898c7ded7d3..f731c1e56475 100644 --- a/Documentation/blackfin/bfin-gpio-notes.txt +++ b/Documentation/blackfin/bfin-gpio-notes.txt @@ -43,7 +43,7 @@ void bfin_gpio_irq_free(unsigned gpio); The request functions will record the function state for a certain pin, - the free functions will clear it's function state. + the free functions will clear its function state. Once a pin is requested, it can't be requested again before it is freed by previous caller, otherwise kernel will dump stacks, and the request function fail. diff --git a/Documentation/cachetlb.txt b/Documentation/cachetlb.txt index 2b5f823abd03..9164ae3b83bc 100644 --- a/Documentation/cachetlb.txt +++ b/Documentation/cachetlb.txt @@ -5,7 +5,7 @@ This document describes the cache/tlb flushing interfaces called by the Linux VM subsystem. It enumerates over each interface, -describes it's intended purpose, and what side effect is expected +describes its intended purpose, and what side effect is expected after the interface is invoked. The side effects described below are stated for a uniprocessor @@ -231,7 +231,7 @@ require a whole different set of interfaces to handle properly. The biggest problem is that of virtual aliasing in the data cache of a processor. -Is your port susceptible to virtual aliasing in it's D-cache? +Is your port susceptible to virtual aliasing in its D-cache? Well, if your D-cache is virtually indexed, is larger in size than PAGE_SIZE, and does not prevent multiple cache lines for the same physical address from existing at once, you have this problem. @@ -249,7 +249,7 @@ one way to solve this (in particular SPARC_FLAG_MMAPSHARED). Next, you have to solve the D-cache aliasing issue for all other cases. Please keep in mind that fact that, for a given page mapped into some user address space, there is always at least one more -mapping, that of the kernel in it's linear mapping starting at +mapping, that of the kernel in its linear mapping starting at PAGE_OFFSET. So immediately, once the first user maps a given physical page into its address space, by implication the D-cache aliasing problem has the potential to exist since the kernel already diff --git a/Documentation/cgroups/memcg_test.txt b/Documentation/cgroups/memcg_test.txt index f7f68b2ac199..b7eececfb195 100644 --- a/Documentation/cgroups/memcg_test.txt +++ b/Documentation/cgroups/memcg_test.txt @@ -244,7 +244,7 @@ Under below explanation, we assume CONFIG_MEM_RES_CTRL_SWAP=y. we have to check if OLDPAGE/NEWPAGE is a valid page after commit(). 8. LRU - Each memcg has its own private LRU. Now, it's handling is under global + Each memcg has its own private LRU. Now, its handling is under global VM's control (means that it's handled under global zone->lru_lock). Almost all routines around memcg's LRU is called by global LRU's list management functions under zone->lru_lock(). diff --git a/Documentation/cgroups/memory.txt b/Documentation/cgroups/memory.txt index 3a6aecd078ba..6cab1f29da4c 100644 --- a/Documentation/cgroups/memory.txt +++ b/Documentation/cgroups/memory.txt @@ -263,7 +263,7 @@ some of the pages cached in the cgroup (page cache pages). 4.2 Task migration -When a task migrates from one cgroup to another, it's charge is not +When a task migrates from one cgroup to another, its charge is not carried forward by default. The pages allocated from the original cgroup still remain charged to it, the charge is dropped when the page is freed or reclaimed. diff --git a/Documentation/connector/connector.txt b/Documentation/connector/connector.txt index 78c9466a9aa8..e5c5f5e6ab70 100644 --- a/Documentation/connector/connector.txt +++ b/Documentation/connector/connector.txt @@ -88,7 +88,7 @@ int cn_netlink_send(struct cn_msg *msg, u32 __groups, int gfp_mask); int gfp_mask - GFP mask. Note: When registering new callback user, connector core assigns - netlink group to the user which is equal to it's id.idx. + netlink group to the user which is equal to its id.idx. /*****************************************/ Protocol description. diff --git a/Documentation/dvb/ci.txt b/Documentation/dvb/ci.txt index 2ecd834585e6..4a0c2b56e690 100644 --- a/Documentation/dvb/ci.txt +++ b/Documentation/dvb/ci.txt @@ -41,7 +41,7 @@ This application requires the following to function properly as of now. * Cards that fall in this category ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ -At present the cards that fall in this category are the Twinhan and it's +At present the cards that fall in this category are the Twinhan and its clones, these cards are available as VVMER, Tomato, Hercules, Orange and so on. diff --git a/Documentation/dvb/contributors.txt b/Documentation/dvb/contributors.txt index 4865addebe1c..47c30098dab6 100644 --- a/Documentation/dvb/contributors.txt +++ b/Documentation/dvb/contributors.txt @@ -1,7 +1,7 @@ Thanks go to the following people for patches and contributions: Michael Hunold - for the initial saa7146 driver and it's recent overhaul + for the initial saa7146 driver and its recent overhaul Christian Theiss for his work on the initial Linux DVB driver diff --git a/Documentation/filesystems/autofs4-mount-control.txt b/Documentation/filesystems/autofs4-mount-control.txt index 8f78ded4b648..51986bf08a4d 100644 --- a/Documentation/filesystems/autofs4-mount-control.txt +++ b/Documentation/filesystems/autofs4-mount-control.txt @@ -146,7 +146,7 @@ found to be inadequate, in this case. The Generic Netlink system was used for this as raw Netlink would lead to a significant increase in complexity. There's no question that the Generic Netlink system is an elegant solution for common case ioctl functions but it's not a complete -replacement probably because it's primary purpose in life is to be a +replacement probably because its primary purpose in life is to be a message bus implementation rather than specifically an ioctl replacement. While it would be possible to work around this there is one concern that lead to the decision to not use it. This is that the autofs diff --git a/Documentation/filesystems/ceph.txt b/Documentation/filesystems/ceph.txt index 0660c9f5deef..763d8ebbbebd 100644 --- a/Documentation/filesystems/ceph.txt +++ b/Documentation/filesystems/ceph.txt @@ -90,7 +90,7 @@ Mount Options Specify the IP and/or port the client should bind to locally. There is normally not much reason to do this. If the IP is not specified, the client's IP address is determined by looking at the - address it's connection to the monitor originates from. + address its connection to the monitor originates from. wsize=X Specify the maximum write size in bytes. By default there is no diff --git a/Documentation/filesystems/dlmfs.txt b/Documentation/filesystems/dlmfs.txt index c50bbb2d52b4..1b528b2ad809 100644 --- a/Documentation/filesystems/dlmfs.txt +++ b/Documentation/filesystems/dlmfs.txt @@ -47,7 +47,7 @@ You'll want to start heartbeating on a volume which all the nodes in your lockspace can access. The easiest way to do this is via ocfs2_hb_ctl (distributed with ocfs2-tools). Right now it requires that an OCFS2 file system be in place so that it can automatically -find it's heartbeat area, though it will eventually support heartbeat +find its heartbeat area, though it will eventually support heartbeat against raw disks. Please see the ocfs2_hb_ctl and mkfs.ocfs2 manual pages distributed diff --git a/Documentation/filesystems/fiemap.txt b/Documentation/filesystems/fiemap.txt index 606233cd4618..1b805a0efbb0 100644 --- a/Documentation/filesystems/fiemap.txt +++ b/Documentation/filesystems/fiemap.txt @@ -38,7 +38,7 @@ flags, it will return EBADR and the contents of fm_flags will contain the set of flags which caused the error. If the kernel is compatible with all flags passed, the contents of fm_flags will be unmodified. It is up to userspace to determine whether rejection of a particular -flag is fatal to it's operation. This scheme is intended to allow the +flag is fatal to its operation. This scheme is intended to allow the fiemap interface to grow in the future but without losing compatibility with old software. @@ -56,7 +56,7 @@ If this flag is set, the kernel will sync the file before mapping extents. * FIEMAP_FLAG_XATTR If this flag is set, the extents returned will describe the inodes -extended attribute lookup tree, instead of it's data tree. +extended attribute lookup tree, instead of its data tree. Extent Mapping @@ -89,7 +89,7 @@ struct fiemap_extent { }; All offsets and lengths are in bytes and mirror those on disk. It is valid -for an extents logical offset to start before the request or it's logical +for an extents logical offset to start before the request or its logical length to extend past the request. Unless FIEMAP_EXTENT_NOT_ALIGNED is returned, fe_logical, fe_physical, and fe_length will be aligned to the block size of the file system. With the exception of extents flagged as @@ -125,7 +125,7 @@ been allocated for the file yet. * FIEMAP_EXTENT_DELALLOC - This will also set FIEMAP_EXTENT_UNKNOWN. -Delayed allocation - while there is data for this extent, it's +Delayed allocation - while there is data for this extent, its physical location has not been allocated yet. * FIEMAP_EXTENT_ENCODED @@ -159,7 +159,7 @@ Data is located within a meta data block. Data is packed into a block with data from other files. * FIEMAP_EXTENT_UNWRITTEN -Unwritten extent - the extent is allocated but it's data has not been +Unwritten extent - the extent is allocated but its data has not been initialized. This indicates the extent's data will be all zero if read through the filesystem but the contents are undefined if read directly from the device. @@ -176,7 +176,7 @@ VFS -> File System Implementation File systems wishing to support fiemap must implement a ->fiemap callback on their inode_operations structure. The fs ->fiemap call is responsible for -defining it's set of supported fiemap flags, and calling a helper function on +defining its set of supported fiemap flags, and calling a helper function on each discovered extent: struct inode_operations { diff --git a/Documentation/filesystems/fuse.txt b/Documentation/filesystems/fuse.txt index 397a41adb4c3..13af4a49e7db 100644 --- a/Documentation/filesystems/fuse.txt +++ b/Documentation/filesystems/fuse.txt @@ -91,7 +91,7 @@ Mount options 'default_permissions' By default FUSE doesn't check file access permissions, the - filesystem is free to implement it's access policy or leave it to + filesystem is free to implement its access policy or leave it to the underlying file access mechanism (e.g. in case of network filesystems). This option enables permission checking, restricting access based on file mode. It is usually useful together with the @@ -171,7 +171,7 @@ or may honor them by sending a reply to the _original_ request, with the error set to EINTR. It is also possible that there's a race between processing the -original request and it's INTERRUPT request. There are two possibilities: +original request and its INTERRUPT request. There are two possibilities: 1) The INTERRUPT request is processed before the original request is processed diff --git a/Documentation/filesystems/hpfs.txt b/Documentation/filesystems/hpfs.txt index fa45c3baed98..74630bd504fb 100644 --- a/Documentation/filesystems/hpfs.txt +++ b/Documentation/filesystems/hpfs.txt @@ -103,7 +103,7 @@ to analyze or change OS2SYS.INI. Codepages HPFS can contain several uppercasing tables for several codepages and each -file has a pointer to codepage it's name is in. However OS/2 was created in +file has a pointer to codepage its name is in. However OS/2 was created in America where people don't care much about codepages and so multiple codepages support is quite buggy. I have Czech OS/2 working in codepage 852 on my disk. Once I booted English OS/2 working in cp 850 and I created a file on my 852 diff --git a/Documentation/filesystems/nfs/rpc-cache.txt b/Documentation/filesystems/nfs/rpc-cache.txt index 8a382bea6808..ebcaaee21616 100644 --- a/Documentation/filesystems/nfs/rpc-cache.txt +++ b/Documentation/filesystems/nfs/rpc-cache.txt @@ -185,7 +185,7 @@ failed lookup meant a definite 'no'. request/response format ----------------------- -While each cache is free to use it's own format for requests +While each cache is free to use its own format for requests and responses over channel, the following is recommended as appropriate and support routines are available to help: Each request or response record should be printable ASCII diff --git a/Documentation/filesystems/proc.txt b/Documentation/filesystems/proc.txt index 770700317c2c..f6b1b5fca1df 100644 --- a/Documentation/filesystems/proc.txt +++ b/Documentation/filesystems/proc.txt @@ -965,7 +965,7 @@ your system and how much traffic was routed over those devices: ...] 1375103 17405 0 0 0 0 0 0 ...] 1703981 5535 0 0 0 3 0 0 -In addition, each Channel Bond interface has it's own directory. For +In addition, each Channel Bond interface has its own directory. For example, the bond0 device will have a directory called /proc/net/bond0/. It will contain information that is specific to that bond, such as the current slaves of the bond, the link status of the slaves, and how @@ -1362,7 +1362,7 @@ been accounted as having caused 1MB of write. In other words: The number of bytes which this process caused to not happen, by truncating pagecache. A task can cause "negative" IO too. If this task truncates some dirty pagecache, some IO which another task has been accounted -for (in it's write_bytes) will not be happening. We _could_ just subtract that +for (in its write_bytes) will not be happening. We _could_ just subtract that from the truncating task's write_bytes, but there is information loss in doing that. diff --git a/Documentation/filesystems/smbfs.txt b/Documentation/filesystems/smbfs.txt index f673ef0de0f7..194fb0decd2c 100644 --- a/Documentation/filesystems/smbfs.txt +++ b/Documentation/filesystems/smbfs.txt @@ -3,6 +3,6 @@ protocol used by Windows for Workgroups, Windows 95 and Windows NT. Smbfs was inspired by Samba, the program written by Andrew Tridgell that turns any Unix host into a file server for DOS or Windows clients. -Smbfs is a SMB client, but uses parts of samba for it's operation. For +Smbfs is a SMB client, but uses parts of samba for its operation. For more info on samba, including documentation, please go to http://www.samba.org/ and then on to your nearest mirror. diff --git a/Documentation/filesystems/vfs.txt b/Documentation/filesystems/vfs.txt index 3de2f32edd90..b66858538df5 100644 --- a/Documentation/filesystems/vfs.txt +++ b/Documentation/filesystems/vfs.txt @@ -72,7 +72,7 @@ structure (this is the kernel-side implementation of file descriptors). The freshly allocated file structure is initialized with a pointer to the dentry and a set of file operation member functions. These are taken from the inode data. The open() file method is then -called so the specific filesystem implementation can do it's work. You +called so the specific filesystem implementation can do its work. You can see that this is another switch performed by the VFS. The file structure is placed into the file descriptor table for the process. diff --git a/Documentation/hwmon/lm85 b/Documentation/hwmon/lm85 index a13680871bc7..a76aefeeb68a 100644 --- a/Documentation/hwmon/lm85 +++ b/Documentation/hwmon/lm85 @@ -157,7 +157,7 @@ temperature configuration points: There are three PWM outputs. The LM85 datasheet suggests that the pwm3 output control both fan3 and fan4. Each PWM can be individually -configured and assigned to a zone for it's control value. Each PWM can be +configured and assigned to a zone for its control value. Each PWM can be configured individually according to the following options. * pwm#_auto_pwm_min - this specifies the PWM value for temp#_auto_temp_off diff --git a/Documentation/input/joystick.txt b/Documentation/input/joystick.txt index 154d767b2acb..8007b7ca87bf 100644 --- a/Documentation/input/joystick.txt +++ b/Documentation/input/joystick.txt @@ -402,7 +402,7 @@ for the port of the SoundFusion is supported by the cs461x.c module. ~~~~~~~~~~~~~~~~~~~~~~~~ The Live! has a special PCI gameport, which, although it doesn't provide any "Enhanced" stuff like 4DWave and friends, is quite a bit faster than -it's ISA counterparts. It also requires special support, hence the +its ISA counterparts. It also requires special support, hence the emu10k1-gp.c module for it instead of the normal ns558.c one. 3.15 SoundBlaster 64 and 128 - ES1370 and ES1371, ESS Solo1 and S3 SonicVibes diff --git a/Documentation/intel_txt.txt b/Documentation/intel_txt.txt index f40a1f030019..1423bcc7c507 100644 --- a/Documentation/intel_txt.txt +++ b/Documentation/intel_txt.txt @@ -126,7 +126,7 @@ o Tboot then applies an (optional) user-defined launch policy to o Tboot adjusts the e820 table provided by the bootloader to reserve its own location in memory as well as to reserve certain other TXT-related regions. -o As part of it's launch, tboot DMA protects all of RAM (using the +o As part of its launch, tboot DMA protects all of RAM (using the VT-d PMRs). Thus, the kernel must be booted with 'intel_iommu=on' in order to remove this blanket protection and use VT-d's page-level protection. diff --git a/Documentation/kbuild/kconfig-language.txt b/Documentation/kbuild/kconfig-language.txt index c412c245848f..b472e4e0ba67 100644 --- a/Documentation/kbuild/kconfig-language.txt +++ b/Documentation/kbuild/kconfig-language.txt @@ -181,7 +181,7 @@ Expressions are listed in decreasing order of precedence. (7) Returns the result of max(/expr/, /expr/). An expression can have a value of 'n', 'm' or 'y' (or 0, 1, 2 -respectively for calculations). A menu entry becomes visible when it's +respectively for calculations). A menu entry becomes visible when its expression evaluates to 'm' or 'y'. There are two types of symbols: constant and non-constant symbols. diff --git a/Documentation/kernel-docs.txt b/Documentation/kernel-docs.txt index 28cdc2af2131..ec8d31ee12e0 100644 --- a/Documentation/kernel-docs.txt +++ b/Documentation/kernel-docs.txt @@ -116,7 +116,7 @@ Author: Ingo Molnar, Gadi Oxman and Miguel de Icaza. URL: http://www.linuxjournal.com/article.php?sid=2391 Keywords: RAID, MD driver. - Description: Linux Journal Kernel Korner article. Here is it's + Description: Linux Journal Kernel Korner article. Here is its abstract: "A description of the implementation of the RAID-1, RAID-4 and RAID-5 personalities of the MD device driver in the Linux kernel, providing users with high performance and reliable, @@ -127,7 +127,7 @@ URL: http://www.linuxjournal.com/article.php?sid=1219 Keywords: device driver, module, loading/unloading modules, allocating resources. - Description: Linux Journal Kernel Korner article. Here is it's + Description: Linux Journal Kernel Korner article. Here is its abstract: "This is the first of a series of four articles co-authored by Alessandro Rubini and Georg Zezchwitz which present a practical approach to writing Linux device drivers as kernel @@ -141,7 +141,7 @@ Keywords: character driver, init_module, clean_up module, autodetection, mayor number, minor number, file operations, open(), close(). - Description: Linux Journal Kernel Korner article. Here is it's + Description: Linux Journal Kernel Korner article. Here is its abstract: "This article, the second of four, introduces part of the actual code to create custom module implementing a character device driver. It describes the code for module initialization and @@ -152,7 +152,7 @@ URL: http://www.linuxjournal.com/article.php?sid=1221 Keywords: read(), write(), select(), ioctl(), blocking/non blocking mode, interrupt handler. - Description: Linux Journal Kernel Korner article. Here is it's + Description: Linux Journal Kernel Korner article. Here is its abstract: "This article, the third of four on writing character device drivers, introduces concepts of reading, writing, and using ioctl-calls". @@ -161,7 +161,7 @@ Author: Alessandro Rubini and Georg v. Zezschwitz. URL: http://www.linuxjournal.com/article.php?sid=1222 Keywords: interrupts, irqs, DMA, bottom halves, task queues. - Description: Linux Journal Kernel Korner article. Here is it's + Description: Linux Journal Kernel Korner article. Here is its abstract: "This is the fourth in a series of articles about writing character device drivers as loadable kernel modules. This month, we further investigate the field of interrupt handling. diff --git a/Documentation/kprobes.txt b/Documentation/kprobes.txt index 2f9115c0ae62..51ec634ac04b 100644 --- a/Documentation/kprobes.txt +++ b/Documentation/kprobes.txt @@ -332,7 +332,7 @@ occurs during execution of kp->pre_handler or kp->post_handler, or during single-stepping of the probed instruction, Kprobes calls kp->fault_handler. Any or all handlers can be NULL. If kp->flags is set KPROBE_FLAG_DISABLED, that kp will be registered but disabled, -so, it's handlers aren't hit until calling enable_kprobe(kp). +so, its handlers aren't hit until calling enable_kprobe(kp). NOTE: 1. With the introduction of the "symbol_name" field to struct kprobe, diff --git a/Documentation/laptops/laptop-mode.txt b/Documentation/laptops/laptop-mode.txt index 2c3c35093023..0bf25eebce94 100644 --- a/Documentation/laptops/laptop-mode.txt +++ b/Documentation/laptops/laptop-mode.txt @@ -207,7 +207,7 @@ Tips & Tricks * Drew Scott Daniels observed: "I don't know why, but when I decrease the number of colours that my display uses it consumes less battery power. I've seen this on powerbooks too. I hope that this is a piece of information that - might be useful to the Laptop Mode patch or it's users." + might be useful to the Laptop Mode patch or its users." * In syslog.conf, you can prefix entries with a dash ``-'' to omit syncing the file after every logging. When you're using laptop-mode and your disk doesn't diff --git a/Documentation/lguest/lguest.c b/Documentation/lguest/lguest.c index 3119f5db75bd..e9ce3c554514 100644 --- a/Documentation/lguest/lguest.c +++ b/Documentation/lguest/lguest.c @@ -263,7 +263,7 @@ static u8 *get_feature_bits(struct device *dev) * Launcher virtual with an offset. * * This can be tough to get your head around, but usually it just means that we - * use these trivial conversion functions when the Guest gives us it's + * use these trivial conversion functions when the Guest gives us its * "physical" addresses: */ static void *from_guest_phys(unsigned long addr) diff --git a/Documentation/md.txt b/Documentation/md.txt index 188f4768f1d5..e4e893ef3e01 100644 --- a/Documentation/md.txt +++ b/Documentation/md.txt @@ -136,7 +136,7 @@ raid_disks != 0. Then uninitialized devices can be added with ADD_NEW_DISK. The structure passed to ADD_NEW_DISK must specify the state of the device -and it's role in the array. +and its role in the array. Once started with RUN_ARRAY, uninitialized spares can be added with HOT_ADD_DISK. diff --git a/Documentation/netlabel/lsm_interface.txt b/Documentation/netlabel/lsm_interface.txt index 98dd9f7430f2..638c74f7de7f 100644 --- a/Documentation/netlabel/lsm_interface.txt +++ b/Documentation/netlabel/lsm_interface.txt @@ -38,7 +38,7 @@ Depending on the exact configuration, translation between the network packet label and the internal LSM security identifier can be time consuming. The NetLabel label mapping cache is a caching mechanism which can be used to sidestep much of this overhead once a mapping has been established. Once the -LSM has received a packet, used NetLabel to decode it's security attributes, +LSM has received a packet, used NetLabel to decode its security attributes, and translated the security attributes into a LSM internal identifier the LSM can use the NetLabel caching functions to associate the LSM internal identifier with the network packet's label. This means that in the future diff --git a/Documentation/networking/ifenslave.c b/Documentation/networking/ifenslave.c index 1b96ccda3836..2bac9618c345 100644 --- a/Documentation/networking/ifenslave.c +++ b/Documentation/networking/ifenslave.c @@ -756,7 +756,7 @@ static int enslave(char *master_ifname, char *slave_ifname) */ if (abi_ver < 1) { /* For old ABI, the master needs to be - * down before setting it's hwaddr + * down before setting its hwaddr */ res = set_if_down(master_ifname, master_flags.ifr_flags); if (res) { diff --git a/Documentation/networking/packet_mmap.txt b/Documentation/networking/packet_mmap.txt index 09ab0d290326..98f71a5cef00 100644 --- a/Documentation/networking/packet_mmap.txt +++ b/Documentation/networking/packet_mmap.txt @@ -100,7 +100,7 @@ by the kernel. The destruction of the socket and all associated resources is done by a simple call to close(fd). -Next I will describe PACKET_MMAP settings and it's constraints, +Next I will describe PACKET_MMAP settings and its constraints, also the mapping of the circular buffer in the user process and the use of this buffer. @@ -432,7 +432,7 @@ TP_STATUS_LOSING : indicates there were packet drops from last time the PACKET_STATISTICS option. TP_STATUS_CSUMNOTREADY: currently it's used for outgoing IP packets which - it's checksum will be done in hardware. So while + its checksum will be done in hardware. So while reading the packet we should not try to check the checksum. diff --git a/Documentation/power/regulator/consumer.txt b/Documentation/power/regulator/consumer.txt index cdebb5145c25..55c4175d8099 100644 --- a/Documentation/power/regulator/consumer.txt +++ b/Documentation/power/regulator/consumer.txt @@ -8,11 +8,11 @@ Please see overview.txt for a description of the terms used in this text. 1. Consumer Regulator Access (static & dynamic drivers) ======================================================= -A consumer driver can get access to it's supply regulator by calling :- +A consumer driver can get access to its supply regulator by calling :- regulator = regulator_get(dev, "Vcc"); -The consumer passes in it's struct device pointer and power supply ID. The core +The consumer passes in its struct device pointer and power supply ID. The core then finds the correct regulator by consulting a machine specific lookup table. If the lookup is successful then this call will return a pointer to the struct regulator that supplies this consumer. @@ -34,7 +34,7 @@ usually be called in your device drivers probe() and remove() respectively. 2. Regulator Output Enable & Disable (static & dynamic drivers) ==================================================================== -A consumer can enable it's power supply by calling:- +A consumer can enable its power supply by calling:- int regulator_enable(regulator); @@ -49,7 +49,7 @@ int regulator_is_enabled(regulator); This will return > zero when the regulator is enabled. -A consumer can disable it's supply when no longer needed by calling :- +A consumer can disable its supply when no longer needed by calling :- int regulator_disable(regulator); @@ -140,7 +140,7 @@ by calling :- int regulator_set_optimum_mode(struct regulator *regulator, int load_uA); This will cause the core to recalculate the total load on the regulator (based -on all it's consumers) and change operating mode (if necessary and permitted) +on all its consumers) and change operating mode (if necessary and permitted) to best match the current operating load. The load_uA value can be determined from the consumers datasheet. e.g.most diff --git a/Documentation/power/regulator/machine.txt b/Documentation/power/regulator/machine.txt index 63728fed620b..bdec39b9bd75 100644 --- a/Documentation/power/regulator/machine.txt +++ b/Documentation/power/regulator/machine.txt @@ -52,7 +52,7 @@ static struct regulator_init_data regulator1_data = { }; Regulator-1 supplies power to Regulator-2. This relationship must be registered -with the core so that Regulator-1 is also enabled when Consumer A enables it's +with the core so that Regulator-1 is also enabled when Consumer A enables its supply (Regulator-2). The supply regulator is set by the supply_regulator_dev field below:- diff --git a/Documentation/power/regulator/overview.txt b/Documentation/power/regulator/overview.txt index ffd185bb6054..9363e056188a 100644 --- a/Documentation/power/regulator/overview.txt +++ b/Documentation/power/regulator/overview.txt @@ -35,16 +35,16 @@ Some terms used in this document:- o Consumer - Electronic device that is supplied power by a regulator. Consumers can be classified into two types:- - Static: consumer does not change it's supply voltage or + Static: consumer does not change its supply voltage or current limit. It only needs to enable or disable it's - power supply. It's supply voltage is set by the hardware, + power supply. Its supply voltage is set by the hardware, bootloader, firmware or kernel board initialisation code. Dynamic: consumer needs to change it's supply voltage or current limit to meet operation demands. - o Power Domain - Electronic circuit that is supplied it's input power by the + o Power Domain - Electronic circuit that is supplied its input power by the output power of a regulator, switch or by another power domain. diff --git a/Documentation/powerpc/booting-without-of.txt b/Documentation/powerpc/booting-without-of.txt index 79f533f38c61..46d22105aa07 100644 --- a/Documentation/powerpc/booting-without-of.txt +++ b/Documentation/powerpc/booting-without-of.txt @@ -1289,7 +1289,7 @@ link between a device node and its interrupt parent in the interrupt tree. The value of interrupt-parent is the phandle of the parent node. -If the interrupt-parent property is not defined for a node, it's +If the interrupt-parent property is not defined for a node, its interrupt parent is assumed to be an ancestor in the node's _device tree_ hierarchy. diff --git a/Documentation/powerpc/phyp-assisted-dump.txt b/Documentation/powerpc/phyp-assisted-dump.txt index c4682b982a2e..ad340205d96a 100644 --- a/Documentation/powerpc/phyp-assisted-dump.txt +++ b/Documentation/powerpc/phyp-assisted-dump.txt @@ -19,7 +19,7 @@ dump offers several strong, practical advantages: immediately available to the system for normal use. -- After the dump is completed, no further reboots are required; the system will be fully usable, and running - in it's normal, production mode on it normal kernel. + in its normal, production mode on its normal kernel. The above can only be accomplished by coordination with, and assistance from the hypervisor. The procedure is diff --git a/Documentation/rt-mutex-design.txt b/Documentation/rt-mutex-design.txt index 4b736d24da7a..8df0b782c4d7 100644 --- a/Documentation/rt-mutex-design.txt +++ b/Documentation/rt-mutex-design.txt @@ -657,7 +657,7 @@ here. The waiter structure has a "task" field that points to the task that is blocked on the mutex. This field can be NULL the first time it goes through the loop -or if the task is a pending owner and had it's mutex stolen. If the "task" +or if the task is a pending owner and had its mutex stolen. If the "task" field is NULL then we need to set up the accounting for it. Task blocks on mutex diff --git a/Documentation/scsi/ChangeLog.lpfc b/Documentation/scsi/ChangeLog.lpfc index 2ffc1148eb95..e759e92e286d 100644 --- a/Documentation/scsi/ChangeLog.lpfc +++ b/Documentation/scsi/ChangeLog.lpfc @@ -707,7 +707,7 @@ Changes from 20040920 to 20041018 * Integrate patches from Christoph Hellwig: two new helpers common to lpfc_sli_resume_iocb and lpfc_sli_issue_iocb - singificant cleanup of those two functions - the unused SLI_IOCB_USE_TXQ is - gone - lpfc_sli_issue_iocb_wait loses it's flags argument + gone - lpfc_sli_issue_iocb_wait loses its flags argument totally. * Fix in lpfc_sli.c: we can not store a 5 bit value in a 4-bit field. @@ -1028,7 +1028,7 @@ Changes from 20040614 to 20040709 * Remove the need for buf_tmo. * Changed ULP_BDE64 to struct ulp_bde64. * Changed ULP_BDE to struct ulp_bde. - * Cleanup lpfc_os_return_scsi_cmd() and it's call path. + * Cleanup lpfc_os_return_scsi_cmd() and its call path. * Removed lpfc_no_device_delay. * Consolidating lpfc_hba_put_event() into lpfc_put_event(). * Removed following attributes and their functionality: diff --git a/Documentation/scsi/FlashPoint.txt b/Documentation/scsi/FlashPoint.txt index d5acaa300a46..1540a92f6d2b 100644 --- a/Documentation/scsi/FlashPoint.txt +++ b/Documentation/scsi/FlashPoint.txt @@ -71,7 +71,7 @@ peters@mylex.com Ever since its introduction last October, the BusLogic FlashPoint LT has been problematic for members of the Linux community, in that no Linux -drivers have been available for this new Ultra SCSI product. Despite it's +drivers have been available for this new Ultra SCSI product. Despite its officially being positioned as a desktop workstation product, and not being particularly well suited for a high performance multitasking operating system like Linux, the FlashPoint LT has been touted by computer system diff --git a/Documentation/scsi/dtc3x80.txt b/Documentation/scsi/dtc3x80.txt index e8ae6230ab3e..1d7af9f9a8ed 100644 --- a/Documentation/scsi/dtc3x80.txt +++ b/Documentation/scsi/dtc3x80.txt @@ -12,7 +12,7 @@ The 3180 does not. Otherwise, they are identical. The DTC3x80 does not support DMA but it does have Pseudo-DMA which is supported by the driver. -It's DTC406 scsi chip is supposedly compatible with the NCR 53C400. +Its DTC406 scsi chip is supposedly compatible with the NCR 53C400. It is memory mapped, uses an IRQ, but no dma or io-port. There is internal DMA, between SCSI bus and an on-chip 128-byte buffer. Double buffering is done automagically by the chip. Data is transferred diff --git a/Documentation/scsi/ncr53c8xx.txt b/Documentation/scsi/ncr53c8xx.txt index 08e2b4d04aab..cda5f8fa2c66 100644 --- a/Documentation/scsi/ncr53c8xx.txt +++ b/Documentation/scsi/ncr53c8xx.txt @@ -1479,7 +1479,7 @@ Wide16 SCSI. Enabling serial NVRAM support enables detection of the serial NVRAM included on Symbios and some Symbios compatible host adaptors, and Tekram boards. The serial NVRAM is used by Symbios and Tekram to hold set up parameters for the -host adaptor and it's attached drives. +host adaptor and its attached drives. The Symbios NVRAM also holds data on the boot order of host adaptors in a system with more than one host adaptor. This enables the order of scanning diff --git a/Documentation/scsi/osst.txt b/Documentation/scsi/osst.txt index f536907e241d..2b21890bc983 100644 --- a/Documentation/scsi/osst.txt +++ b/Documentation/scsi/osst.txt @@ -40,7 +40,7 @@ behavior looks very much the same as st to the userspace applications. History ------- -In the first place, osst shared it's identity very much with st. That meant +In the first place, osst shared its identity very much with st. That meant that it used the same kernel structures and the same device node as st. So you could only have either of them being present in the kernel. This has been fixed by registering an own device, now. diff --git a/Documentation/scsi/scsi_fc_transport.txt b/Documentation/scsi/scsi_fc_transport.txt index aec6549ab097..e00192de4d1c 100644 --- a/Documentation/scsi/scsi_fc_transport.txt +++ b/Documentation/scsi/scsi_fc_transport.txt @@ -70,7 +70,7 @@ Overview: up to an administrative entity controlling the vport. For example, if vports are to be associated with virtual machines, a XEN mgmt utility would be responsible for creating wwpn/wwnn's for the vport, - using it's own naming authority and OUI. (Note: it already does this + using its own naming authority and OUI. (Note: it already does this for virtual MAC addresses). @@ -81,7 +81,7 @@ Device Trees and Vport Objects: with rports and scsi target objects underneath it. Currently the FC transport creates the vport object and places it under the scsi_host object corresponding to the physical adapter. The LLDD will allocate - a new scsi_host for the vport and link it's object under the vport. + a new scsi_host for the vport and link its object under the vport. The remainder of the tree under the vports scsi_host is the same as the non-NPIV case. The transport is written currently to easily allow the parent of the vport to be something other than the scsi_host. diff --git a/Documentation/scsi/sym53c8xx_2.txt b/Documentation/scsi/sym53c8xx_2.txt index eb9a7b905b64..6f63b7989679 100644 --- a/Documentation/scsi/sym53c8xx_2.txt +++ b/Documentation/scsi/sym53c8xx_2.txt @@ -687,7 +687,7 @@ maintain the driver code. Enabling serial NVRAM support enables detection of the serial NVRAM included on Symbios and some Symbios compatible host adaptors, and Tekram boards. The serial NVRAM is used by Symbios and Tekram to hold set up parameters for the -host adaptor and it's attached drives. +host adaptor and its attached drives. The Symbios NVRAM also holds data on the boot order of host adaptors in a system with more than one host adaptor. This information is no longer used diff --git a/Documentation/sound/alsa/soc/dapm.txt b/Documentation/sound/alsa/soc/dapm.txt index 9ac842be9b4f..05bf5a0eee41 100644 --- a/Documentation/sound/alsa/soc/dapm.txt +++ b/Documentation/sound/alsa/soc/dapm.txt @@ -188,8 +188,8 @@ The WM8731 output mixer has 3 inputs (sources) 3. Mic Sidetone Input Each input in this example has a kcontrol associated with it (defined in example -above) and is connected to the output mixer via it's kcontrol name. We can now -connect the destination widget (wrt audio signal) with it's source widgets. +above) and is connected to the output mixer via its kcontrol name. We can now +connect the destination widget (wrt audio signal) with its source widgets. /* output mixer */ {"Output Mixer", "Line Bypass Switch", "Line Input"}, diff --git a/Documentation/sound/alsa/soc/machine.txt b/Documentation/sound/alsa/soc/machine.txt index bab7711ce963..2524c75557df 100644 --- a/Documentation/sound/alsa/soc/machine.txt +++ b/Documentation/sound/alsa/soc/machine.txt @@ -67,7 +67,7 @@ static struct snd_soc_dai_link corgi_dai = { .ops = &corgi_ops, }; -struct snd_soc_card then sets up the machine with it's DAIs. e.g. +struct snd_soc_card then sets up the machine with its DAIs. e.g. /* corgi audio machine driver */ static struct snd_soc_card snd_soc_corgi = { diff --git a/Documentation/sound/alsa/soc/overview.txt b/Documentation/sound/alsa/soc/overview.txt index 1e4c6d3655f2..138ac88c1461 100644 --- a/Documentation/sound/alsa/soc/overview.txt +++ b/Documentation/sound/alsa/soc/overview.txt @@ -33,7 +33,7 @@ features :- and machines. * Easy I2S/PCM audio interface setup between codec and SoC. Each SoC - interface and codec registers it's audio interface capabilities with the + interface and codec registers its audio interface capabilities with the core and are subsequently matched and configured when the application hardware parameters are known. diff --git a/Documentation/usb/WUSB-Design-overview.txt b/Documentation/usb/WUSB-Design-overview.txt index c480e9c32dbd..4c5e37939344 100644 --- a/Documentation/usb/WUSB-Design-overview.txt +++ b/Documentation/usb/WUSB-Design-overview.txt @@ -381,7 +381,7 @@ descriptor that gives us the status of the transfer, its identification we issue another URB to read into the destination buffer the chunk of data coming out of the remote endpoint. Done, wait for the next guy. The callbacks for the URBs issued from here are the ones that will declare -the xfer complete at some point and call it's callback. +the xfer complete at some point and call its callback. Seems simple, but the implementation is not trivial. diff --git a/Documentation/vm/numa_memory_policy.txt b/Documentation/vm/numa_memory_policy.txt index be45dbb9d7f2..6690fc34ef6d 100644 --- a/Documentation/vm/numa_memory_policy.txt +++ b/Documentation/vm/numa_memory_policy.txt @@ -45,7 +45,7 @@ most general to most specific: to establish the task policy for a child task exec()'d from an executable image that has no awareness of memory policy. See the MEMORY POLICY APIS section, below, for an overview of the system call - that a task may use to set/change it's task/process policy. + that a task may use to set/change its task/process policy. In a multi-threaded task, task policies apply only to the thread [Linux kernel task] that installs the policy and any threads @@ -301,7 +301,7 @@ decrement this reference count, respectively. mpol_put() will only free the structure back to the mempolicy kmem cache when the reference count goes to zero. -When a new memory policy is allocated, it's reference count is initialized +When a new memory policy is allocated, its reference count is initialized to '1', representing the reference held by the task that is installing the new policy. When a pointer to a memory policy structure is stored in another structure, another reference is added, as the task's reference will be dropped diff --git a/Documentation/w1/w1.generic b/Documentation/w1/w1.generic index e3333eec4320..212f4ac31c01 100644 --- a/Documentation/w1/w1.generic +++ b/Documentation/w1/w1.generic @@ -25,7 +25,7 @@ When a w1 master driver registers with the w1 subsystem, the following occurs: - sysfs entries for that w1 master are created - the w1 bus is periodically searched for new slave devices -When a device is found on the bus, w1 core checks if driver for it's family is +When a device is found on the bus, w1 core checks if driver for its family is loaded. If so, the family driver is attached to the slave. If there is no driver for the family, default one is assigned, which allows to perform almost any kind of operations. Each logical operation is a transaction -- cgit v1.2.3 From d4dfd7278eade24c4aa4b36b8df981fab04f2f26 Mon Sep 17 00:00:00 2001 From: Hidetoshi Seto Date: Thu, 15 Apr 2010 13:08:24 +0900 Subject: PCI: aerdrv, doc: update example output in pcieaer-howto.txt Follow new format. Signed-off-by: Hidetoshi Seto Reviewed-by: Kenji Kaneshige Signed-off-by: Jesse Barnes --- Documentation/PCI/pcieaer-howto.txt | 14 +++++--------- 1 file changed, 5 insertions(+), 9 deletions(-) (limited to 'Documentation/PCI') diff --git a/Documentation/PCI/pcieaer-howto.txt b/Documentation/PCI/pcieaer-howto.txt index be21001ab144..8c406a496799 100644 --- a/Documentation/PCI/pcieaer-howto.txt +++ b/Documentation/PCI/pcieaer-howto.txt @@ -71,15 +71,11 @@ console. If it's a correctable error, it is outputed as a warning. Otherwise, it is printed as an error. So users could choose different log level to filter out correctable error messages. -Below shows an example. -+------ PCI-Express Device Error -----+ -Error Severity : Uncorrected (Fatal) -PCIE Bus Error type : Transaction Layer -Unsupported Request : First -Requester ID : 0500 -VendorID=8086h, DeviceID=0329h, Bus=05h, Device=00h, Function=00h -TLB Header: -04000001 00200a03 05010000 00050100 +Below shows an example: +0000:50:00.0: PCIe Bus Error: severity=Uncorrected (Fatal), type=Transaction Layer, id=0500(Requester ID) +0000:50:00.0: device [8086:0329] error status/mask=00100000/00000000 +0000:50:00.0: [20] Unsupported Request (First) +0000:50:00.0: TLP Header: 04000001 00200a03 05010000 00050100 In the example, 'Requester ID' means the ID of the device who sends the error message to root port. Pls. refer to pci express specs for -- cgit v1.2.3 From 89713422a768458a0d375f0c2f3586cd5ccde6a1 Mon Sep 17 00:00:00 2001 From: Hidetoshi Seto Date: Thu, 15 Apr 2010 13:21:27 +0900 Subject: PCI: aerdrv: introduce default_downstream_reset_link I noticed that when I inject a fatal error to an endpoint via aer-inject, aer_root_reset() is called as reset_link for a downstream port at upstream of the endpoint: pcieport 0000:00:06.0: AER: Uncorrected (Fatal) error received: id=5401 : pcieport 0000:52:02.0: Root Port link has been reset It externally appears to be working, but internally issues some accesses to PCI_ERR_ROOT_COMMAND/STATUS registers that is for root port so not available on downstream port. This patch introduces default_downstream_reset_link that is a version of aer_root_reset() with no accesses to root port's register. It is used for downstream ports that has no reset_link function its specific. This patch also updates related description in pcieaer-howto.txt. Some minor fixes are included. Signed-off-by: Hidetoshi Seto Reviewed-by: Kenji Kaneshige Signed-off-by: Jesse Barnes --- Documentation/PCI/pcieaer-howto.txt | 15 +++---- drivers/pci/pcie/aer/aerdrv.c | 23 +---------- drivers/pci/pcie/aer/aerdrv.h | 1 + drivers/pci/pcie/aer/aerdrv_core.c | 78 +++++++++++++++++++++++++++++-------- 4 files changed, 71 insertions(+), 46 deletions(-) (limited to 'Documentation/PCI') diff --git a/Documentation/PCI/pcieaer-howto.txt b/Documentation/PCI/pcieaer-howto.txt index 8c406a496799..26d3d945c3c2 100644 --- a/Documentation/PCI/pcieaer-howto.txt +++ b/Documentation/PCI/pcieaer-howto.txt @@ -13,7 +13,7 @@ Reporting (AER) driver and provides information on how to use it, as well as how to enable the drivers of endpoint devices to conform with PCI Express AER driver. -1.2 Copyright © Intel Corporation 2006. +1.2 Copyright (C) Intel Corporation 2006. 1.3 What is the PCI Express AER Driver? @@ -108,7 +108,7 @@ but the PCI Express link itself is fully functional. Fatal errors, on the other hand, cause the link to be unreliable. When AER is enabled, a PCI Express device will automatically send an -error message to the PCIE root port above it when the device captures +error message to the PCIe root port above it when the device captures an error. The Root Port, upon receiving an error reporting message, internally processes and logs the error message in its PCI Express capability structure. Error information being logged includes storing @@ -194,8 +194,9 @@ to reset link, AER port service driver is required to provide the function to reset link. Firstly, kernel looks for if the upstream component has an aer driver. If it has, kernel uses the reset_link callback of the aer driver. If the upstream component has no aer driver -and the port is downstream port, we will use the aer driver of the -root port who reports the AER error. As for upstream ports, +and the port is downstream port, we will perform a hot reset as the +default by setting the Secondary Bus Reset bit of the Bridge Control +register associated with the downstream port. As for upstream ports, they should provide their own aer service drivers with reset_link function. If error_detected returns PCI_ERS_RESULT_CAN_RECOVER and reset_link returns PCI_ERS_RESULT_RECOVERED, the error handling goes @@ -249,11 +250,11 @@ cleanup uncorrectable status register. Pls. refer to section 3.3. 4. Software error injection -Debugging PCIE AER error recovery code is quite difficult because it +Debugging PCIe AER error recovery code is quite difficult because it is hard to trigger real hardware errors. Software based error -injection can be used to fake various kinds of PCIE errors. +injection can be used to fake various kinds of PCIe errors. -First you should enable PCIE AER software error injection in kernel +First you should enable PCIe AER software error injection in kernel configuration, that is, following item should be in your .config. CONFIG_PCIEAER_INJECT=y or CONFIG_PCIEAER_INJECT=m diff --git a/drivers/pci/pcie/aer/aerdrv.c b/drivers/pci/pcie/aer/aerdrv.c index cbc7cc77b2c3..a225d58c1ac8 100644 --- a/drivers/pci/pcie/aer/aerdrv.c +++ b/drivers/pci/pcie/aer/aerdrv.c @@ -341,7 +341,6 @@ static int __devinit aer_probe(struct pcie_device *dev) **/ static pci_ers_result_t aer_root_reset(struct pci_dev *dev) { - u16 p2p_ctrl; u32 reg32; int pos; @@ -352,27 +351,7 @@ static pci_ers_result_t aer_root_reset(struct pci_dev *dev) reg32 &= ~ROOT_PORT_INTR_ON_MESG_MASK; pci_write_config_dword(dev, pos + PCI_ERR_ROOT_COMMAND, reg32); - /* Assert Secondary Bus Reset */ - pci_read_config_word(dev, PCI_BRIDGE_CONTROL, &p2p_ctrl); - p2p_ctrl |= PCI_BRIDGE_CTL_BUS_RESET; - pci_write_config_word(dev, PCI_BRIDGE_CONTROL, p2p_ctrl); - - /* - * we should send hot reset message for 2ms to allow it time to - * propogate to all downstream ports - */ - msleep(2); - - /* De-assert Secondary Bus Reset */ - p2p_ctrl &= ~PCI_BRIDGE_CTL_BUS_RESET; - pci_write_config_word(dev, PCI_BRIDGE_CONTROL, p2p_ctrl); - - /* - * System software must wait for at least 100ms from the end - * of a reset of one or more device before it is permitted - * to issue Configuration Requests to those devices. - */ - msleep(200); + aer_do_secondary_bus_reset(dev); dev_printk(KERN_DEBUG, &dev->dev, "Root Port link has been reset\n"); /* Clear Root Error Status */ diff --git a/drivers/pci/pcie/aer/aerdrv.h b/drivers/pci/pcie/aer/aerdrv.h index d0f8291c5ca0..7aaae2d2bd67 100644 --- a/drivers/pci/pcie/aer/aerdrv.h +++ b/drivers/pci/pcie/aer/aerdrv.h @@ -114,6 +114,7 @@ static inline pci_ers_result_t merge_result(enum pci_ers_result orig, } extern struct bus_type pcie_port_bus_type; +extern void aer_do_secondary_bus_reset(struct pci_dev *dev); extern int aer_init(struct pcie_device *dev); extern void aer_isr(struct work_struct *work); extern void aer_print_error(struct pci_dev *dev, struct aer_err_info *info); diff --git a/drivers/pci/pcie/aer/aerdrv_core.c b/drivers/pci/pcie/aer/aerdrv_core.c index 8fb14aeb74dd..ce42cac99dd3 100644 --- a/drivers/pci/pcie/aer/aerdrv_core.c +++ b/drivers/pci/pcie/aer/aerdrv_core.c @@ -373,6 +373,53 @@ static pci_ers_result_t broadcast_error_message(struct pci_dev *dev, return result_data.result; } +/** + * aer_do_secondary_bus_reset - perform secondary bus reset + * @dev: pointer to bridge's pci_dev data structure + * + * Invoked when performing link reset at Root Port or Downstream Port. + */ +void aer_do_secondary_bus_reset(struct pci_dev *dev) +{ + u16 p2p_ctrl; + + /* Assert Secondary Bus Reset */ + pci_read_config_word(dev, PCI_BRIDGE_CONTROL, &p2p_ctrl); + p2p_ctrl |= PCI_BRIDGE_CTL_BUS_RESET; + pci_write_config_word(dev, PCI_BRIDGE_CONTROL, p2p_ctrl); + + /* + * we should send hot reset message for 2ms to allow it time to + * propagate to all downstream ports + */ + msleep(2); + + /* De-assert Secondary Bus Reset */ + p2p_ctrl &= ~PCI_BRIDGE_CTL_BUS_RESET; + pci_write_config_word(dev, PCI_BRIDGE_CONTROL, p2p_ctrl); + + /* + * System software must wait for at least 100ms from the end + * of a reset of one or more device before it is permitted + * to issue Configuration Requests to those devices. + */ + msleep(200); +} + +/** + * default_downstream_reset_link - default reset function for Downstream Port + * @dev: pointer to downstream port's pci_dev data structure + * + * Invoked when performing link reset at Downstream Port w/ no aer driver. + */ +static pci_ers_result_t default_downstream_reset_link(struct pci_dev *dev) +{ + aer_do_secondary_bus_reset(dev); + dev_printk(KERN_DEBUG, &dev->dev, + "Downstream Port link has been reset\n"); + return PCI_ERS_RESULT_RECOVERED; +} + static int find_aer_service_iter(struct device *device, void *data) { struct pcie_port_service_driver *service_driver, **drv; @@ -406,31 +453,28 @@ static pci_ers_result_t reset_link(struct pcie_device *aerdev, pci_ers_result_t status; struct pcie_port_service_driver *driver; - if (dev->hdr_type & PCI_HEADER_TYPE_BRIDGE) + if (dev->hdr_type & PCI_HEADER_TYPE_BRIDGE) { + /* Reset this port for all subordinates */ udev = dev; - else + } else { + /* Reset the upstream component (likely downstream port) */ udev = dev->bus->self; + } /* Use the aer driver of the component firstly */ driver = find_aer_service(udev); - /* - * If it hasn't the driver and is downstream port, use the root port's - */ - if (!driver || !driver->reset_link) { - if (udev->pcie_type == PCI_EXP_TYPE_DOWNSTREAM && - aerdev->device.driver && - to_service_driver(aerdev->device.driver)->reset_link) { - driver = to_service_driver(aerdev->device.driver); - } else { - dev_printk(KERN_DEBUG, &dev->dev, - "no link-reset support at upstream device %s\n", - pci_name(udev)); - return PCI_ERS_RESULT_DISCONNECT; - } + if (driver && driver->reset_link) { + status = driver->reset_link(udev); + } else if (udev->pcie_type == PCI_EXP_TYPE_DOWNSTREAM) { + status = default_downstream_reset_link(udev); + } else { + dev_printk(KERN_DEBUG, &dev->dev, + "no link-reset support at upstream device %s\n", + pci_name(udev)); + return PCI_ERS_RESULT_DISCONNECT; } - status = driver->reset_link(udev); if (status != PCI_ERS_RESULT_RECOVERED) { dev_printk(KERN_DEBUG, &dev->dev, "link reset at upstream device %s failed\n", -- cgit v1.2.3