[PATCHv9 10/10] ARM: dma-mapping: add support for IOMMU mapper

Paul Gortmaker paul.gortmaker at windriver.com
Thu May 10 22:08:39 EDT 2012

On Wed, Apr 18, 2012 at 9:44 AM, Marek Szyprowski
<m.szyprowski at samsung.com> wrote:
> This patch add a complete implementation of DMA-mapping API for
> devices which have IOMMU support.

Hi Marek,

It looks like this patch breaks no-MMU builds on ARM, at least
according to git bisect.  Here is a link to a linux-next failure:


arch/arm/mm/dma-mapping.c:726:42: error: 'pgprot_kernel' undeclared
(first use in this function)
make[2]: *** [arch/arm/mm/dma-mapping.o] Error 1

Please have a look, thanks.


> This implementation tries to optimize dma address space usage by remapping
> all possible physical memory chunks into a single dma address space chunk.
> DMA address space is managed on top of the bitmap stored in the
> dma_iommu_mapping structure stored in device->archdata. Platform setup
> code has to initialize parameters of the dma address space (base address,
> size, allocation precision order) with arm_iommu_create_mapping()
> function.
> To reduce the size of the bitmap, all allocations are aligned to the
> specified order of base 4 KiB pages.
> dma_alloc_* functions allocate physical memory in chunks, each with
> alloc_pages() function to avoid failing if the physical memory gets
> fragmented. In worst case the allocated buffer is composed of 4 KiB page
> chunks.
> dma_map_sg() function minimizes the total number of dma address space
> chunks by merging of physical memory chunks into one larger dma address
> space chunk. If requested chunk (scatter list entry) boundaries
> match physical page boundaries, most calls to dma_map_sg() requests will
> result in creating only one chunk in dma address space.
> dma_map_page() simply creates a mapping for the given page(s) in the dma
> address space.
> All dma functions also perform required cache operation like their
> counterparts from the arm linear physical memory mapping version.
> This patch contains code and fixes kindly provided by:
> - Krishna Reddy <vdumpa at nvidia.com>,
> - Andrzej Pietrasiewicz <andrzej.p at samsung.com>,
> - Hiroshi DOYU <hdoyu at nvidia.com>
> Signed-off-by: Marek Szyprowski <m.szyprowski at samsung.com>
> Acked-by: Kyungmin Park <kyungmin.park at samsung.com>
> Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk at oracle.com>
> Tested-By: Subash Patel <subash.ramaswamy at linaro.org>
> ---
>  arch/arm/Kconfig                 |    8 +
>  arch/arm/include/asm/device.h    |    3 +
>  arch/arm/include/asm/dma-iommu.h |   34 ++
>  arch/arm/mm/dma-mapping.c        |  727
> +++++++++++++++++++++++++++++++++++++-
>  arch/arm/mm/vmregion.h           |    2 +-
>  5 files changed, 759 insertions(+), 15 deletions(-)
>  create mode 100644 arch/arm/include/asm/dma-iommu.h

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