2012/10/15 Marek Szyprowski m.szyprowski@samsung.com:
Hello,
Some devices, which have IOMMU, for some use cases might require to allocate a buffers for DMA which is contiguous in physical memory. Such use cases appears for example in DRM subsystem when one wants to improve performance or use secure buffer protection.
I would like to ask if adding a new attribute, as proposed in this RFC is a good idea? I feel that it might be an attribute just for a single driver, but I would like to know your opinion. Should we look for other solution?
In addition, currently we have worked dma-mapping-based iommu support for exynos drm driver with this patch set so this patch set has been tested with iommu enabled exynos drm driver and worked fine. actually, this feature is needed for secure mode such as TrustZone. in case of Exynos SoC, memory region for secure mode should be physically contiguous and also maybe OMAP but now dma-mapping framework doesn't guarantee physically continuous memory allocation so this patch set would make it possible.
Tested-by: Inki Dae inki.dae@samsung.com Reviewed-by: Inki Dae inki.dae@samsung.com
Thanks, Inki Dae
Best regards
Marek Szyprowski Samsung Poland R&D Center
Marek Szyprowski (2): common: DMA-mapping: add DMA_ATTR_FORCE_CONTIGUOUS attribute ARM: dma-mapping: add support for DMA_ATTR_FORCE_CONTIGUOUS attribute
Documentation/DMA-attributes.txt | 9 +++++++++ arch/arm/mm/dma-mapping.c | 41 ++++++++++++++++++++++++++++++-------- include/linux/dma-attrs.h | 1 + 3 files changed, 43 insertions(+), 8 deletions(-)
-- 1.7.9.5
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