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Commit b1b39b23 authored by Liam Mark's avatar Liam Mark Committed by Patrick Daly
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common: DMA-mapping: add per-buffer coherent mappings attributes 



The DMA_ATTR_FORCE_COHERENT DMA attribute can be used to force a buffer
to be mapped as IO coherent.

The DMA_ATTR_FORCE_NON_COHERENT DMA attribute can be used to force a
buffer to not be mapped as IO coherent.

Change-Id: Id80d77a5ccd797eec36b45b320423fb46c9f5861
Signed-off-by: default avatarLiam Mark <lmark@codeaurora.org>
Signed-off-by: default avatarPatrick Daly <pdaly@codeaurora.org>
parent 3ba41cfc

Documentation/DMA-attributes.txt

+19 −0
Original line number Diff line number Diff line
@@ -176,3 +176,22 @@ DMA_ATTR_IOMMU_USE_UPSTREAM_HINT 
DMA_ATTR_IOMMU_USE_UPSTREAM_HINT: Normally an smmu will override any bus

attributes (i.e cacheablilty) provided by the client device. Some hardware

may be designed to use the original attributes instead.



DMA_ATTR_FORCE_COHERENT

-----------------------



When passed to a DMA map call the DMA_ATTR_FORCE_COHERENT DMA

attribute can be used to force a buffer to be mapped as IO coherent.

This DMA attribute is only currently supported for arm64 stage 1 IOMMU

mappings.



DMA_ATTR_FORCE_NON_COHERENT

---------------------------



When passed to a DMA map call the DMA_ATTR_FORCE_NON_COHERENT DMA

attribute can be used to force a buffer to not be mapped as IO

coherent.

The DMA_ATTR_FORCE_NON_COHERENT DMA attribute overrides the buffer IO

coherency configuration set by making the device IO coherent.

This DMA attribute is only currently supported for arm64 stage 1 IOMMU

mappings.

include/linux/dma-mapping.h

+11 −0
Original line number Diff line number Diff line
@@ -87,6 +87,17 @@ 
 * may be designed to use the original attributes instead.

 */

#define DMA_ATTR_IOMMU_USE_UPSTREAM_HINT	(1UL << 13)

/*

 * When passed to a DMA map call the DMA_ATTR_FORCE_COHERENT DMA

 * attribute can be used to force a buffer to be mapped as IO coherent.

 */

#define DMA_ATTR_FORCE_COHERENT			(1UL << 14)

/*

 * When passed to a DMA map call the DMA_ATTR_FORCE_NON_COHERENT DMA

 * attribute can be used to force a buffer to not be mapped as IO

 * coherent.

 */

#define DMA_ATTR_FORCE_NON_COHERENT		(1UL << 15)



/*

 * A dma_addr_t can hold any valid DMA or bus address for the platform.