diff options
Diffstat (limited to 'Documentation/core-api')
| -rw-r--r-- | Documentation/core-api/dma-api.rst | 71 | ||||
| -rw-r--r-- | Documentation/core-api/printk-formats.rst | 35 |
2 files changed, 104 insertions, 2 deletions
diff --git a/Documentation/core-api/dma-api.rst b/Documentation/core-api/dma-api.rst index 8e3cce3d0a23..2ad08517e626 100644 --- a/Documentation/core-api/dma-api.rst +++ b/Documentation/core-api/dma-api.rst @@ -530,6 +530,77 @@ routines, e.g.::: .... } +Part Ie - IOVA-based DMA mappings +--------------------------------- + +These APIs allow a very efficient mapping when using an IOMMU. They are an +optional path that requires extra code and are only recommended for drivers +where DMA mapping performance, or the space usage for storing the DMA addresses +matter. All the considerations from the previous section apply here as well. + +:: + + bool dma_iova_try_alloc(struct device *dev, struct dma_iova_state *state, + phys_addr_t phys, size_t size); + +Is used to try to allocate IOVA space for mapping operation. If it returns +false this API can't be used for the given device and the normal streaming +DMA mapping API should be used. The ``struct dma_iova_state`` is allocated +by the driver and must be kept around until unmap time. + +:: + + static inline bool dma_use_iova(struct dma_iova_state *state) + +Can be used by the driver to check if the IOVA-based API is used after a +call to dma_iova_try_alloc. This can be useful in the unmap path. + +:: + + int dma_iova_link(struct device *dev, struct dma_iova_state *state, + phys_addr_t phys, size_t offset, size_t size, + enum dma_data_direction dir, unsigned long attrs); + +Is used to link ranges to the IOVA previously allocated. The start of all +but the first call to dma_iova_link for a given state must be aligned +to the DMA merge boundary returned by ``dma_get_merge_boundary())``, and +the size of all but the last range must be aligned to the DMA merge boundary +as well. + +:: + + int dma_iova_sync(struct device *dev, struct dma_iova_state *state, + size_t offset, size_t size); + +Must be called to sync the IOMMU page tables for IOVA-range mapped by one or +more calls to ``dma_iova_link()``. + +For drivers that use a one-shot mapping, all ranges can be unmapped and the +IOVA freed by calling: + +:: + + void dma_iova_destroy(struct device *dev, struct dma_iova_state *state, + size_t mapped_len, enum dma_data_direction dir, + unsigned long attrs); + +Alternatively drivers can dynamically manage the IOVA space by unmapping +and mapping individual regions. In that case + +:: + + void dma_iova_unlink(struct device *dev, struct dma_iova_state *state, + size_t offset, size_t size, enum dma_data_direction dir, + unsigned long attrs); + +is used to unmap a range previously mapped, and + +:: + + void dma_iova_free(struct device *dev, struct dma_iova_state *state); + +is used to free the IOVA space. All regions must have been unmapped using +``dma_iova_unlink()`` before calling ``dma_iova_free()``. Part II - Non-coherent DMA allocations -------------------------------------- diff --git a/Documentation/core-api/printk-formats.rst b/Documentation/core-api/printk-formats.rst index 4bdc394e86af..4b7f3646ec6c 100644 --- a/Documentation/core-api/printk-formats.rst +++ b/Documentation/core-api/printk-formats.rst @@ -571,9 +571,8 @@ struct clk :: %pC pll1 - %pCn pll1 -For printing struct clk structures. %pC and %pCn print the name of the clock +For printing struct clk structures. %pC prints the name of the clock (Common Clock Framework) or a unique 32-bit ID (legacy clock framework). Passed by reference. @@ -648,6 +647,38 @@ Examples:: %p4cc Y10 little-endian (0x20303159) %p4cc NV12 big-endian (0xb231564e) +Generic FourCC code +------------------- + +:: + %p4c[h[R]lb] gP00 (0x67503030) + +Print a generic FourCC code, as both ASCII characters and its numerical +value as hexadecimal. + +The generic FourCC code is always printed in the big-endian format, +the most significant byte first. This is the opposite of V4L/DRM FourCCs. + +The additional ``h``, ``hR``, ``l``, and ``b`` specifiers define what +endianness is used to load the stored bytes. The data might be interpreted +using the host, reversed host byte order, little-endian, or big-endian. + +Passed by reference. + +Examples for a little-endian machine, given &(u32)0x67503030:: + + %p4ch gP00 (0x67503030) + %p4chR 00Pg (0x30305067) + %p4cl gP00 (0x67503030) + %p4cb 00Pg (0x30305067) + +Examples for a big-endian machine, given &(u32)0x67503030:: + + %p4ch gP00 (0x67503030) + %p4chR 00Pg (0x30305067) + %p4cl 00Pg (0x30305067) + %p4cb gP00 (0x67503030) + Rust ---- |