diff options
Diffstat (limited to 'Documentation')
| -rw-r--r-- | Documentation/DMA-API-HOWTO.txt | 29 | ||||
| -rw-r--r-- | Documentation/DMA-API.txt | 30 | ||||
| -rw-r--r-- | Documentation/devicetree/bindings/pci/xgene-pci-msi.txt | 68 |
3 files changed, 100 insertions, 27 deletions
diff --git a/Documentation/DMA-API-HOWTO.txt b/Documentation/DMA-API-HOWTO.txt index 0f7afb2bb442..aef8cc5a677b 100644 --- a/Documentation/DMA-API-HOWTO.txt +++ b/Documentation/DMA-API-HOWTO.txt @@ -25,13 +25,18 @@ physical addresses. These are the addresses in /proc/iomem. The physical address is not directly useful to a driver; it must use ioremap() to map the space and produce a virtual address. -I/O devices use a third kind of address: a "bus address" or "DMA address". -If a device has registers at an MMIO address, or if it performs DMA to read -or write system memory, the addresses used by the device are bus addresses. -In some systems, bus addresses are identical to CPU physical addresses, but -in general they are not. IOMMUs and host bridges can produce arbitrary +I/O devices use a third kind of address: a "bus address". If a device has +registers at an MMIO address, or if it performs DMA to read or write system +memory, the addresses used by the device are bus addresses. In some +systems, bus addresses are identical to CPU physical addresses, but in +general they are not. IOMMUs and host bridges can produce arbitrary mappings between physical and bus addresses. +From a device's point of view, DMA uses the bus address space, but it may +be restricted to a subset of that space. For example, even if a system +supports 64-bit addresses for main memory and PCI BARs, it may use an IOMMU +so devices only need to use 32-bit DMA addresses. + Here's a picture and some examples: CPU CPU Bus @@ -72,11 +77,11 @@ can use virtual address X to access the buffer, but the device itself cannot because DMA doesn't go through the CPU virtual memory system. In some simple systems, the device can do DMA directly to physical address -Y. But in many others, there is IOMMU hardware that translates bus +Y. But in many others, there is IOMMU hardware that translates DMA addresses to physical addresses, e.g., it translates Z to Y. This is part of the reason for the DMA API: the driver can give a virtual address X to an interface like dma_map_single(), which sets up any required IOMMU -mapping and returns the bus address Z. The driver then tells the device to +mapping and returns the DMA address Z. The driver then tells the device to do DMA to Z, and the IOMMU maps it to the buffer at address Y in system RAM. @@ -98,7 +103,7 @@ First of all, you should make sure #include <linux/dma-mapping.h> is in your driver, which provides the definition of dma_addr_t. This type -can hold any valid DMA or bus address for the platform and should be used +can hold any valid DMA address for the platform and should be used everywhere you hold a DMA address returned from the DMA mapping functions. What memory is DMA'able? @@ -316,7 +321,7 @@ 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 bus space. However, for future compatibility you should + bits of the DMA space. However, for future compatibility you should set the consistent mask even if this default is fine for your driver. @@ -403,7 +408,7 @@ 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 virtual address and the DMA bus address are both +The CPU virtual address and the DMA 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 @@ -645,8 +650,8 @@ PLEASE NOTE: The 'nents' argument to the dma_unmap_sg call must be 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 and -you could render the machine unusable by consuming all bus addresses. +counterpart, because the DMA address space is a shared resource and +you could render the machine unusable by consuming all DMA 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 diff --git a/Documentation/DMA-API.txt b/Documentation/DMA-API.txt index 52088408668a..7eba542eff7c 100644 --- a/Documentation/DMA-API.txt +++ b/Documentation/DMA-API.txt @@ -18,10 +18,10 @@ Part I - dma_ API To get the dma_ API, you must #include <linux/dma-mapping.h>. This provides dma_addr_t and the interfaces described below. -A dma_addr_t can hold any valid DMA or bus address for the platform. It -can be given to a device to use as a DMA source or target. A CPU cannot -reference a dma_addr_t directly because there may be translation between -its physical address space and the bus address space. +A dma_addr_t can hold any valid DMA address for the platform. It can be +given to a device to use as a DMA source or target. A CPU cannot reference +a dma_addr_t directly because there may be translation between its physical +address space and the DMA address space. Part Ia - Using large DMA-coherent buffers ------------------------------------------ @@ -42,7 +42,7 @@ It returns a pointer to the allocated region (in the processor's virtual address space) or NULL if the allocation failed. It also returns a <dma_handle> which may be cast to an unsigned integer the -same width as the bus and given to the device as the bus address base of +same width as the bus and given to the device as the DMA address base of the region. Note: consistent memory can be expensive on some platforms, and the @@ -193,7 +193,7 @@ dma_map_single(struct device *dev, void *cpu_addr, size_t size, enum dma_data_direction direction) Maps a piece of processor virtual memory so it can be accessed by the -device and returns the bus address of the memory. +device and returns the DMA address of the memory. The direction for both APIs may be converted freely by casting. However the dma_ API uses a strongly typed enumerator for its @@ -212,20 +212,20 @@ contiguous piece of memory. For this reason, memory to be mapped by this API should be obtained from sources which guarantee it to be physically contiguous (like kmalloc). -Further, the bus address of the memory must be within the +Further, the DMA address of the memory must be within the dma_mask of the device (the dma_mask is a bit mask of the -addressable region for the device, i.e., if the bus address of -the memory ANDed with the dma_mask is still equal to the bus +addressable region for the device, i.e., if the DMA address of +the memory ANDed with the dma_mask is still equal to the DMA address, then the device can perform DMA to the memory). To ensure that the memory allocated by kmalloc is within the dma_mask, the driver may specify various platform-dependent flags to restrict -the bus address range of the allocation (e.g., on x86, GFP_DMA -guarantees to be within the first 16MB of available bus addresses, +the DMA address range of the allocation (e.g., on x86, GFP_DMA +guarantees to be within the first 16MB of available DMA addresses, as required by ISA devices). Note also that the above constraints on physical contiguity and dma_mask may not apply if the platform has an IOMMU (a device which -maps an I/O bus address to a physical memory address). However, to be +maps an I/O DMA address to a physical memory address). However, to be portable, device driver writers may *not* assume that such an IOMMU exists. @@ -296,7 +296,7 @@ reduce current DMA mapping usage or delay and try again later). dma_map_sg(struct device *dev, struct scatterlist *sg, int nents, enum dma_data_direction direction) -Returns: the number of bus address segments mapped (this may be shorter +Returns: the number of DMA address segments mapped (this may be shorter than <nents> passed in if some elements of the scatter/gather list are physically or virtually adjacent and an IOMMU maps them with a single entry). @@ -340,7 +340,7 @@ must be the same as those and passed in to the scatter/gather mapping API. Note: <nents> must be the number you passed in, *not* the number of -bus address entries returned. +DMA address entries returned. void dma_sync_single_for_cpu(struct device *dev, dma_addr_t dma_handle, size_t size, @@ -507,7 +507,7 @@ it's asked for coherent memory for this device. phys_addr is the CPU physical address to which the memory is currently assigned (this will be ioremapped so the CPU can access the region). -device_addr is the bus address the device needs to be programmed +device_addr is the DMA address the device needs to be programmed with to actually address this memory (this will be handed out as the dma_addr_t in dma_alloc_coherent()). diff --git a/Documentation/devicetree/bindings/pci/xgene-pci-msi.txt b/Documentation/devicetree/bindings/pci/xgene-pci-msi.txt new file mode 100644 index 000000000000..36d881c8e6d4 --- /dev/null +++ b/Documentation/devicetree/bindings/pci/xgene-pci-msi.txt @@ -0,0 +1,68 @@ +* AppliedMicro X-Gene v1 PCIe MSI controller + +Required properties: + +- compatible: should be "apm,xgene1-msi" to identify + X-Gene v1 PCIe MSI controller block. +- msi-controller: indicates that this is X-Gene v1 PCIe MSI controller node +- reg: physical base address (0x79000000) and length (0x900000) for controller + registers. These registers include the MSI termination address and data + registers as well as the MSI interrupt status registers. +- reg-names: not required +- interrupts: A list of 16 interrupt outputs of the controller, starting from + interrupt number 0x10 to 0x1f. +- interrupt-names: not required + +Each PCIe node needs to have property msi-parent that points to msi controller node + +Examples: + +SoC DTSI: + + + MSI node: + msi@79000000 { + compatible = "apm,xgene1-msi"; + msi-controller; + reg = <0x00 0x79000000 0x0 0x900000>; + interrupts = <0x0 0x10 0x4> + <0x0 0x11 0x4> + <0x0 0x12 0x4> + <0x0 0x13 0x4> + <0x0 0x14 0x4> + <0x0 0x15 0x4> + <0x0 0x16 0x4> + <0x0 0x17 0x4> + <0x0 0x18 0x4> + <0x0 0x19 0x4> + <0x0 0x1a 0x4> + <0x0 0x1b 0x4> + <0x0 0x1c 0x4> + <0x0 0x1d 0x4> + <0x0 0x1e 0x4> + <0x0 0x1f 0x4>; + }; + + + PCIe controller node with msi-parent property pointing to MSI node: + pcie0: pcie@1f2b0000 { + status = "disabled"; + device_type = "pci"; + compatible = "apm,xgene-storm-pcie", "apm,xgene-pcie"; + #interrupt-cells = <1>; + #size-cells = <2>; + #address-cells = <3>; + reg = < 0x00 0x1f2b0000 0x0 0x00010000 /* Controller registers */ + 0xe0 0xd0000000 0x0 0x00040000>; /* PCI config space */ + reg-names = "csr", "cfg"; + ranges = <0x01000000 0x00 0x00000000 0xe0 0x10000000 0x00 0x00010000 /* io */ + 0x02000000 0x00 0x80000000 0xe1 0x80000000 0x00 0x80000000>; /* mem */ + dma-ranges = <0x42000000 0x80 0x00000000 0x80 0x00000000 0x00 0x80000000 + 0x42000000 0x00 0x00000000 0x00 0x00000000 0x80 0x00000000>; + interrupt-map-mask = <0x0 0x0 0x0 0x7>; + interrupt-map = <0x0 0x0 0x0 0x1 &gic 0x0 0xc2 0x1 + 0x0 0x0 0x0 0x2 &gic 0x0 0xc3 0x1 + 0x0 0x0 0x0 0x3 &gic 0x0 0xc4 0x1 + 0x0 0x0 0x0 0x4 &gic 0x0 0xc5 0x1>; + dma-coherent; + clocks = <&pcie0clk 0>; + msi-parent= <&msi>; + }; |