diff options
| author |   José Pekkarinen <jose.pekkarinen@nokia.com> | 2016-04-11 10:41:07 +0300 |
|---|---|---|
| committer | José Pekkarinen <jose.pekkarinen@nokia.com> | 2016-04-13 08:17:18 +0300 |
| commit | e09b41010ba33a20a87472ee821fa407a5b8da36 (patch) | |
| tree | d10dc367189862e7ca5c592f033dc3726e1df4e3 /kernel/Documentation/DMA-API-HOWTO.txt | |
| parent | f93b97fd65072de626c074dbe099a1fff05ce060 (diff) | |
These changes are the raw update to linux-4.4.6-rt14. Kernel sources
are taken from kernel.org, and rt patch from the rt wiki download page.
During the rebasing, the following patch collided:
Force tick interrupt and get rid of softirq magic(I70131fb85).
Collisions have been removed because its logic was found on the
source already.
Change-Id: I7f57a4081d9deaa0d9ccfc41a6c8daccdee3b769
Signed-off-by: José Pekkarinen <jose.pekkarinen@nokia.com>
Diffstat (limited to 'kernel/Documentation/DMA-API-HOWTO.txt')
| -rw-r--r-- | kernel/Documentation/DMA-API-HOWTO.txt | 9 |
1 files changed, 7 insertions, 2 deletions
diff --git a/kernel/Documentation/DMA-API-HOWTO.txt b/kernel/Documentation/DMA-API-HOWTO.txt index aef8cc5a6..d69b3fc64 100644 --- a/kernel/Documentation/DMA-API-HOWTO.txt +++ b/kernel/Documentation/DMA-API-HOWTO.txt @@ -245,7 +245,7 @@ the case would look like this: if (!dma_set_mask_and_coherent(dev, DMA_BIT_MASK(64))) { using_dac = 1; - consistent_using_dac = 1; + consistent_using_dac = 1; } else if (!dma_set_mask_and_coherent(dev, DMA_BIT_MASK(32))) { using_dac = 0; consistent_using_dac = 0; @@ -358,7 +358,7 @@ There are two types of DMA mappings: transfer, unmapped right after it (unless you use dma_sync_* below) and for which hardware can optimize for sequential accesses. - This of "streaming" as "asynchronous" or "outside the coherency + Think of "streaming" as "asynchronous" or "outside the coherency domain". Good examples of what to use streaming mappings for are: @@ -681,6 +681,11 @@ or: as appropriate. +PLEASE NOTE: The 'nents' argument to dma_sync_sg_for_cpu() and + dma_sync_sg_for_device() must be the same passed to + dma_map_sg(). It is _NOT_ the count returned by + dma_map_sg(). + After the last DMA transfer call one of the DMA unmap routines dma_unmap_{single,sg}(). If you don't touch the data from the first dma_map_*() call till dma_unmap_*(), then you don't have to call the |