diff --git a/[refs] b/[refs] index 79cb21d2be36..6d9a99a82c42 100644 --- a/[refs] +++ b/[refs] @@ -1,2 +1,2 @@ --- -refs/heads/master: 4ae9ca825e3e28441ef8155c1a81e4c14dfbf38d +refs/heads/master: 2fd74e25df46ecb0b54700aba242dcaeb2d75f4a diff --git a/trunk/Documentation/DMA-API-HOWTO.txt b/trunk/Documentation/DMA-API-HOWTO.txt index bfd94e90af51..98ce51796f71 100644 --- a/trunk/Documentation/DMA-API-HOWTO.txt +++ b/trunk/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