diff options
| author | Laura Abbott <lauraa@codeaurora.org> | 2012-10-29 13:08:03 -0700 |
|---|---|---|
| committer | Srinivas Kandagatla <srinivas.kandagatla@linaro.org> | 2015-11-17 09:22:24 +0000 |
| commit | 73b3b3f5c3c04d6ebd005d1cfd3195a868b9cd4f (patch) | |
| tree | ecc05be5a7b20051b88e84657d8e5e376292842a /Documentation | |
| parent | e29c46e421c100b6fc2d40b3d04a8d6350eca605 (diff) | |
common: DMA-mapping: Add strongly ordered memory attribute
Strongly ordered memory is occasionally needed for some DMA
allocations for specialized use cases. Add the corresponding
DMA attribute.
Change-Id: Idd9e756c242ef57d6fa6700e51cc38d0863b760d
Signed-off-by: Laura Abbott <lauraa@codeaurora.org>
Signed-off-by: Stanimir Varbanov <stanimir.varbanov@linaro.org>
Diffstat (limited to 'Documentation')
| -rw-r--r-- | Documentation/DMA-attributes.txt | 9 |
1 files changed, 9 insertions, 0 deletions
diff --git a/Documentation/DMA-attributes.txt b/Documentation/DMA-attributes.txt index 18dc52c4f2a0..9ac45c33c568 100644 --- a/Documentation/DMA-attributes.txt +++ b/Documentation/DMA-attributes.txt @@ -100,3 +100,12 @@ allocated by dma_alloc_attrs() function from individual pages if it can be mapped as contiguous chunk into device dma address space. By specifying this attribute the allocated buffer is forced to be contiguous also in physical memory. + +DMA_ATTR_STRONGLY_ORDERED +------------------------- + +DMA_ATTR_STRONGLY_ORDERED allocates memory with a very restrictive type +of mapping (no unaligned accesses, no re-ordering, no write merging, no +buffering, no pre-fetching). This has severe performance penalties and +should not be used for general purpose DMA allocations. It should only +be used if one of the restrictions on strongly ordered memory is required. |