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ANDROID: iommu/dma: Add support fo DMA_ATTR_SYS_CACHE_ONLY

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IOMMU_SYS_CACHE_ONLY allows buffers for non-coherent devices
to be mapped with the correct memory attributes so that the buffers
can be cached in the system cache. However, this property
is only usable by drivers that invoke the IOMMU API directly;
it is not usable by drivers that use the DMA API.

Thus, introduce DMA_ATTR_SYS_CACHE_ONLY, so that drivers for
non-coherent devices that use the DMA API can use it to specify if
they want a buffer to be cached in the system cache.

Bug: 176778547
Change-Id: I849d7a3f36b689afd2f6ee400507223fd6395158
Signed-off-by: Isaac J. Manjarres <isaacm@codeaurora.org>
This commit is contained in:
Isaac J. Manjarres 2021-01-04 17:54:07 -08:00 committed by Suren Baghdasaryan
parent 261c5080bb
commit 0b653f27bb
3 changed files with 12 additions and 0 deletions
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2
drivers/iommu/dma-iommu.c
View File

@ -432,6 +432,8 @@ static int dma_info_to_prot(enum dma_data_direction dir, bool coherent,
if (attrs & DMA_ATTR_PRIVILEGED)
prot |= IOMMU_PRIV;
if (attrs & DMA_ATTR_SYS_CACHE_ONLY)
prot |= IOMMU_SYS_CACHE_ONLY;
switch (dir) {
case DMA_BIDIRECTIONAL:

8
include/linux/dma-mapping.h
View File

@ -61,6 +61,14 @@
*/
#define DMA_ATTR_PRIVILEGED (1UL << 9)
/*
* DMA_ATTR_SYS_CACHE_ONLY: used to indicate that the buffer should be mapped
* with the correct memory attributes so that it can be cached in the system
* or last level cache. This is useful for buffers that are being mapped for
* devices that are non-coherent, but can use the system cache.
*/
#define DMA_ATTR_SYS_CACHE_ONLY (1UL << 10)
/*
* A dma_addr_t can hold any valid DMA or bus address for the platform. It can
* be given to a device to use as a DMA source or target. It is specific to a

2
kernel/dma/mapping.c
View File

@ -348,6 +348,8 @@ pgprot_t dma_pgprot(struct device *dev, pgprot_t prot, unsigned long attrs)
if (attrs & DMA_ATTR_WRITE_COMBINE)
return pgprot_writecombine(prot);
#endif
if (attrs & DMA_ATTR_SYS_CACHE_ONLY)
return pgprot_syscached(prot);
return pgprot_dmacoherent(prot);
}
#endif /* CONFIG_MMU */