Messages in this thread Patch in this message | | | Date | Sat, 22 May 2010 09:37:51 +0900 | Subject | [PATCH -mm] Documentation/DMA-API-HOWTO: add ARCH_KMALLOC_MINALIGN description | From | FUJITA Tomonori <> |
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Adds ARCH_KMALLOC_MINALIGN description in "Platform Issues" section.
Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp> --- Documentation/DMA-API-HOWTO.txt | 15 ++++++++++++++- 1 files changed, 14 insertions(+), 1 deletions(-)
diff --git a/Documentation/DMA-API-HOWTO.txt b/Documentation/DMA-API-HOWTO.txt index bfd94e9..98ce517 100644 --- a/Documentation/DMA-API-HOWTO.txt +++ b/Documentation/DMA-API-HOWTO.txt @@ -738,7 +738,20 @@ to "Closing". CONFIG_NEED_SG_DMA_LENGTH if the architecture supports IOMMUs (including software IOMMU). -2) More to come... +2) ARCH_KMALLOC_MINALIGN + + Architectures must ensure that kmalloc'ed buffer is + DMA-safe. Drivers and subsystems depend on it. If an architecture + isn't fully DMA-coherent (i.e. hardware doesn't ensure that data in + the CPU cache is identical to data in main memory), + ARCH_KMALLOC_MINALIGN must be set so that the memory allocator + makes sure that kmalloc'ed buffer doesn't share a cache line with + the others. See arch/arm/include/asm/cache.h as an example. + + Note that ARCH_KMALLOC_MINALIGN is about DMA memory alignment + constraints. You don't need to worry about the architecture data + alignment constraints (e.g. the alignment constraints about 64-bit + objects). Closing -- 1.6.5
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