diff options
| author | FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp> | 2010-05-26 14:44:23 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2010-05-27 09:12:53 -0700 |
| commit | 2fd74e25df46ecb0b54700aba242dcaeb2d75f4a (patch) | |
| tree | 0887964694be2ab02233a3842f5d19b72d38a0fa | |
| parent | 4ae9ca825e3e28441ef8155c1a81e4c14dfbf38d (diff) | |
| download | lwn-2fd74e25df46ecb0b54700aba242dcaeb2d75f4a.tar.gz lwn-2fd74e25df46ecb0b54700aba242dcaeb2d75f4a.zip | |
Documentation/DMA-API-HOWTO: add ARCH_KMALLOC_MINALIGN description
Add ARCH_KMALLOC_MINALIGN description in "Platform Issues" section.
Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Matt Mackall <mpm@selenic.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
| -rw-r--r-- | 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 bfd94e90af51..98ce51796f71 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 |