Messages in this thread Patch in this message | | | Date | Fri, 02 Sep 2011 12:31:34 +0300 | From | Eli Billauer <> | Subject | [PATCH] arch/microblaze: Added sync method support for DMA and made refinements |
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Hi,
This was supposed to be a small patch, but as I dug in, I found that several things needed fixing. The sync support was tested by using a hardware driver which calls these methods extensively. Scatter-gather methods remain completely untested. General DMA operations work, or the system would crash, I suppose.
Here's a summary of the changes:
* Added support for sync_single_for_*
* Added support for sync_sg_for_*
* Removed the previous (static) function __dma_sync_page() in favor of __dma_sync(), so a single function can be used for all needs. This (inline) function was moved to dma_mapping.h, since it's used by dma_cache_sync() there.
* Cache is now flushed on all dma mapping functions, regardless of direction. It's obvious for DMA_TO_DEVICE, but not so obvious regarding DMA_FROM_DEVICE. The reason in the latter case is that an unflushed cache line will be written back to memory sooner or later, possibly overwriting DMAed data.
* Cache is never invalidated on dma mapping. It's pointless, since the CPU isn't supposed to touch the memory segment anyhow until unmap or sync.
* dma_cache_sync() now really syncs the cache (is was effectively a NOP)
Patch follows.
Eli
Signed-off-by: Eli Billauer <eli.billauer@gmail.com> --- arch/microblaze/include/asm/dma-mapping.h | 20 +++++- arch/microblaze/kernel/dma.c | 109 ++++++++++++++++++++++------- 2 files changed, 101 insertions(+), 28 deletions(-)
diff --git a/arch/microblaze/include/asm/dma-mapping.h b/arch/microblaze/include/asm/dma-mapping.h index 8fbb0ec..cddeca5 100644 --- a/arch/microblaze/include/asm/dma-mapping.h +++ b/arch/microblaze/include/asm/dma-mapping.h @@ -28,12 +28,12 @@ #include <linux/dma-attrs.h> #include <asm/io.h> #include <asm-generic/dma-coherent.h> +#include <asm/cacheflush.h> #define DMA_ERROR_CODE (~(dma_addr_t)0x0) #define __dma_alloc_coherent(dev, gfp, size, handle) NULL #define __dma_free_coherent(size, addr) ((void)0) -#define __dma_sync(addr, size, rw) ((void)0) static inline unsigned long device_to_mask(struct device *dev) { @@ -95,6 +95,22 @@ static inline int dma_set_mask(struct device *dev, u64 dma_mask) #include <asm-generic/dma-mapping-common.h> +static inline void __dma_sync(unsigned long paddr, + size_t size, enum dma_data_direction direction) +{ + switch (direction) { + case DMA_TO_DEVICE: + case DMA_BIDIRECTIONAL: + flush_dcache_range(paddr, paddr + size); + break; + case DMA_FROM_DEVICE: + invalidate_dcache_range(paddr, paddr + size); + break; + default: + BUG(); + } +} + static inline int dma_mapping_error(struct device *dev, dma_addr_t dma_addr) { struct dma_map_ops *ops = get_dma_ops(dev); @@ -135,7 +151,7 @@ static inline void dma_cache_sync(struct device *dev, void *vaddr, size_t size, enum dma_data_direction direction) { BUG_ON(direction == DMA_NONE); - __dma_sync(vaddr, size, (int)direction); + __dma_sync(virt_to_phys(vaddr), size, (int)direction); } #endif /* _ASM_MICROBLAZE_DMA_MAPPING_H */ diff --git a/arch/microblaze/kernel/dma.c b/arch/microblaze/kernel/dma.c index 393e6b2..9fa9d82 100644 --- a/arch/microblaze/kernel/dma.c +++ b/arch/microblaze/kernel/dma.c @@ -11,7 +11,6 @@ #include <linux/gfp.h> #include <linux/dma-debug.h> #include <asm/bug.h> -#include <asm/cacheflush.h> /* * Generic direct DMA implementation @@ -21,21 +20,6 @@ * can set archdata.dma_data to an unsigned long holding the offset. By * default the offset is PCI_DRAM_OFFSET. */ -static inline void __dma_sync_page(unsigned long paddr, unsigned long offset, - size_t size, enum dma_data_direction direction) -{ - switch (direction) { - case DMA_TO_DEVICE: - case DMA_BIDIRECTIONAL: - flush_dcache_range(paddr + offset, paddr + offset + size); - break; - case DMA_FROM_DEVICE: - invalidate_dcache_range(paddr + offset, paddr + offset + size); - break; - default: - BUG(); - } -} static unsigned long get_dma_direct_offset(struct device *dev) { @@ -91,17 +75,24 @@ static int dma_direct_map_sg(struct device *dev, struct scatterlist *sgl, /* FIXME this part of code is untested */ for_each_sg(sgl, sg, nents, i) { sg->dma_address = sg_phys(sg) + get_dma_direct_offset(dev); - __dma_sync_page(page_to_phys(sg_page(sg)), sg->offset, - sg->length, direction); + __dma_sync(page_to_phys(sg_page(sg)) + sg->offset, + sg->length, DMA_TO_DEVICE); } return nents; } -static void dma_direct_unmap_sg(struct device *dev, struct scatterlist *sg, +static void dma_direct_unmap_sg(struct device *dev, struct scatterlist *sgl, int nents, enum dma_data_direction direction, struct dma_attrs *attrs) { + struct scatterlist *sg; + int i; + + /* FIXME this part of code is untested */ + if (direction == DMA_FROM_DEVICE) + for_each_sg(sgl, sg, nents, i) + __dma_sync(sg->dma_address, sg->length, direction); } static int dma_direct_dma_supported(struct device *dev, u64 mask) @@ -116,7 +107,15 @@ static inline dma_addr_t dma_direct_map_page(struct device *dev, enum dma_data_direction direction, struct dma_attrs *attrs) { - __dma_sync_page(page_to_phys(page), offset, size, direction); + /* We're before the DMA transfer, so cache invalidation makes no + sense in the case of DMA_FROM_DEVICE. Flushing is necessary + in either case, or an unflushed cache line may overwrite + data written by device, in the event of that line being allocated + for other use. Calling __dma_sync with DMA_TO_DEVICE makes this + flush. + */ + + __dma_sync(page_to_phys(page) + offset, size, DMA_TO_DEVICE); return page_to_phys(page) + offset + get_dma_direct_offset(dev); } @@ -126,12 +125,66 @@ static inline void dma_direct_unmap_page(struct device *dev, enum dma_data_direction direction, struct dma_attrs *attrs) { -/* There is not necessary to do cache cleanup - * - * phys_to_virt is here because in __dma_sync_page is __virt_to_phys and - * dma_address is physical address - */ - __dma_sync_page(dma_address, 0 , size, direction); +/* On a DMA to the device, the data has already been flushed and read by + the device at the point unmapping is done. No point doing anything. + In the other direction, unmapping may be used just before accessing the + data on the CPU, so cache invalidation is necessary. +*/ + + if (direction == DMA_FROM_DEVICE) + __dma_sync(dma_address, size, direction); +} + +static inline void +dma_direct_sync_single_for_cpu(struct device *dev, + dma_addr_t dma_handle, size_t size, + enum dma_data_direction direction) +{ + /* It's pointless to invalidate the cache if the device isn't supposed + to write to the relevant region */ + + if (direction == DMA_FROM_DEVICE) + __dma_sync(dma_handle, size, direction); +} + +static inline void +dma_direct_sync_single_for_device(struct device *dev, + dma_addr_t dma_handle, size_t size, + enum dma_data_direction direction) +{ + /* It's pointless to flush the cache if the CPU isn't supposed + to write to the relevant region */ + + if (direction == DMA_TO_DEVICE) + __dma_sync(dma_handle, size, direction); +} + +static inline void +dma_direct_sync_sg_for_cpu(struct device *dev, + struct scatterlist *sgl, int nents, + enum dma_data_direction direction) +{ + struct scatterlist *sg; + int i; + + /* FIXME this part of code is untested */ + if (direction == DMA_FROM_DEVICE) + for_each_sg(sgl, sg, nents, i) + __dma_sync(sg->dma_address, sg->length, direction); +} + +static inline void +dma_direct_sync_sg_for_device(struct device *dev, + struct scatterlist *sgl, int nents, + enum dma_data_direction direction) +{ + struct scatterlist *sg; + int i; + + /* FIXME this part of code is untested */ + if (direction == DMA_TO_DEVICE) + for_each_sg(sgl, sg, nents, i) + __dma_sync(sg->dma_address, sg->length, direction); } struct dma_map_ops dma_direct_ops = { @@ -142,6 +195,10 @@ struct dma_map_ops dma_direct_ops = { .dma_supported = dma_direct_dma_supported, .map_page = dma_direct_map_page, .unmap_page = dma_direct_unmap_page, + .sync_single_for_cpu = dma_direct_sync_single_for_cpu, + .sync_single_for_device = dma_direct_sync_single_for_device, + .sync_sg_for_cpu = dma_direct_sync_sg_for_cpu, + .sync_sg_for_device = dma_direct_sync_sg_for_device, }; EXPORT_SYMBOL(dma_direct_ops); -- 1.7.2.2
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