Currently, IOMMU_QCOM_SYS_CACHE exists to allow non-coherent I/O masters on Qualcomm SoCs to upgrade to caching their buffers in the outer-level/system cache on these platforms. However, these masters are limited to managing the mapping of these buffers themselves through the IOMMU framework, as opposed to allowing the DMA-IOMMU framework to handle it, since there is no DMA attribute that maps to the IOMMU_QCOM_SYS_CACHE protection bit.
Thus, introduce DMA_ATTR_SYS_CACHE so that clients can use the DMA-IOMMU layer to map their DMA buffers with the correct memory attributes to allow the buffers to be cached in the outer-level/system cache. Signed-off-by: Isaac J. Manjarres <[email protected]> --- drivers/iommu/dma-iommu.c | 2 ++ include/linux/dma-mapping.h | 8 ++++++++ 2 files changed, 10 insertions(+) diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c index f321279..c433ece 100644 --- a/drivers/iommu/dma-iommu.c +++ b/drivers/iommu/dma-iommu.c @@ -369,6 +369,8 @@ 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) + prot |= IOMMU_QCOM_SYS_CACHE; switch (dir) { case DMA_BIDIRECTIONAL: diff --git a/include/linux/dma-mapping.h b/include/linux/dma-mapping.h index 4a1c4fc..bdd4dcf 100644 --- a/include/linux/dma-mapping.h +++ b/include/linux/dma-mapping.h @@ -71,6 +71,14 @@ #define DMA_ATTR_PRIVILEGED (1UL << 9) /* + * DMA_ATTR_SYS_CACHE: This is a hint that non-coherent masters can use to + * tell the DMA-IOMMU layer to map their DMA buffers with the correct memory + * attributes that allow these buffers to be cached in an outer-level/system + * cache. + */ +#define DMA_ATTR_SYS_CACHE (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. A CPU cannot * reference a dma_addr_t directly because there may be translation between -- The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum, a Linux Foundation Collaborative Project _______________________________________________ iommu mailing list [email protected] https://lists.linuxfoundation.org/mailman/listinfo/iommu
