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arm64: dma-mapping: optimize unmap coherency check

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Change arm_iommu_unmap_page to check the DMA attributes for buffer
coherency support instead of checking the iommu page table.

This change now requires that clients correctly set the
DMA_ATTR_FORCE_COHERENT or DMA_ATTR_FORCE_NON_COHERENT DMA
attributes in their unmap call if they used it with their map call.

This will improve the performance of the arm_iommu_unmap_page
call.

Change-Id: Ie96ef0a1906a8732b7b1eef7bed8aa85abee95f4
Signed-off-by: Liam Mark <lmark@codeaurora.org>
This commit is contained in:
Liam Mark 2017-02-24 11:32:17 -08:00
parent 98094e2149
commit 37a29f1605
2 changed files with 10 additions and 3 deletions
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9
Documentation/DMA-attributes.txt
View file

@ -132,6 +132,11 @@ 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.
When the DMA_ATTR_FORCE_COHERENT attribute is set during a map call ensure
that it is also set during for the matching unmap call to ensure that the
correct cache maintenance is carried out.
This DMA attribute is only currently supported for arm64 stage 1 IOMMU
mappings.
@ -143,5 +148,9 @@ coherent.
The DMA_ATTR_FORCE_NON_COHERENT DMA attribute overrides the buffer IO
coherency configuration set by making the device IO coherent.
When the DMA_ATTR_FORCE_NON_COHERENT attribute is set during a map call
ensure that it is also set during for the matching unmap call to ensure
that the correct cache maintenance is carried out.
This DMA attribute is only currently supported for arm64 stage 1 IOMMU
mappings.

4
arch/arm64/mm/dma-mapping.c
View file

@ -1821,10 +1821,8 @@ static void arm_iommu_unmap_page(struct device *dev, dma_addr_t handle,
mapping->domain, iova));
int offset = handle & ~PAGE_MASK;
int len = PAGE_ALIGN(size + offset);
bool iova_coherent = iommu_is_iova_coherent(mapping->domain,
handle);
if (!(iova_coherent ||
if (!(is_dma_coherent(dev, attrs) ||
dma_get_attr(DMA_ATTR_SKIP_CPU_SYNC, attrs)))
__dma_page_dev_to_cpu(page, offset, size, dir);