2012/10/15 Marek Szyprowski [off-list ref]:

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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