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| author | Vinod Koul <vinod.koul@intel.com> | 2015-08-05 08:42:06 +0530 |
|---|---|---|
| committer | Vinod Koul <vinod.koul@intel.com> | 2015-08-17 13:46:22 +0530 |
| commit | 60884ddecdc2f45fd2862b7e95c9ad858584f82b (patch) | |
| tree | 9322caa2d629a2d4f8c3957ad091ce0206ed31f5 /Documentation/dmaengine | |
| parent | 06f10e2f936424496d44e5541c220845c8c55345 (diff) | |
| download | linux-60884ddecdc2f45fd2862b7e95c9ad858584f82b.tar.bz2 | |
Documentation: dmaengine: Add DMA_CTRL_REUSE documentation
Signed-off-by: Vinod Koul <vinod.koul@intel.com>
Acked-by:Robert Jarzmik <robert.jarzmik@free.fr>
Diffstat (limited to 'Documentation/dmaengine')
| -rw-r--r-- | Documentation/dmaengine/provider.txt | 17 |
1 files changed, 17 insertions, 0 deletions
diff --git a/Documentation/dmaengine/provider.txt b/Documentation/dmaengine/provider.txt index 243889ec5c5a..67d4ce4df109 100644 --- a/Documentation/dmaengine/provider.txt +++ b/Documentation/dmaengine/provider.txt @@ -351,6 +351,23 @@ where to put them) - This can be acked by invoking async_tx_ack() - If set, does not mean descriptor can be reused + * DMA_CTRL_REUSE + - If set, the descriptor can be reused after being completed. It should + not be freed by provider if this flag is set. + - The descriptor should be prepared for reuse by invoking + dmaengine_desc_set_reuse() which will set DMA_CTRL_REUSE. + - dmaengine_desc_set_reuse() will succeed only when channel support + reusable descriptor as exhibited by capablities + - As a consequence, if a device driver wants to skip the dma_map_sg() and + dma_unmap_sg() in between 2 transfers, because the DMA'd data wasn't used, + it can resubmit the transfer right after its completion. + - Descriptor can be freed in few ways + - Clearing DMA_CTRL_REUSE by invoking dmaengine_desc_clear_reuse() + and submitting for last txn + - Explicitly invoking dmaengine_desc_free(), this can succeed only + when DMA_CTRL_REUSE is already set + - Terminating the channel + General Design Notes -------------------- |