arm64: dma-mapping: optimize unmap coherency check
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>
diff --git a/Documentation/DMA-attributes.txt b/Documentation/DMA-attributes.txt
index d534246..01e865d 100644
--- a/Documentation/DMA-attributes.txt
+++ b/Documentation/DMA-attributes.txt
@@ -182,6 +182,11 @@
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.
@@ -193,5 +198,10 @@
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.
diff --git a/arch/arm64/mm/dma-mapping.c b/arch/arm64/mm/dma-mapping.c
index fb958a6..ad8f2b3 100644
--- a/arch/arm64/mm/dma-mapping.c
+++ b/arch/arm64/mm/dma-mapping.c
@@ -1800,10 +1800,8 @@
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) ||
(attrs & DMA_ATTR_SKIP_CPU_SYNC)))
__dma_page_dev_to_cpu(page, offset, size, dir);