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dmaengine: add fence support

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Some engines optimize operation by reading ahead in the descriptor chain
such that descriptor2 may start execution before descriptor1 completes.
If descriptor2 depends on the result from descriptor1 then a fence is
required (on descriptor2) to disable this optimization.  The async_tx
api could implicitly identify dependencies via the 'depend_tx'
parameter, but that would constrain cases where the dependency chain
only specifies a completion order rather than a data dependency.  So,
provide an ASYNC_TX_FENCE to explicitly identify data dependencies.

Signed-off-by: Dan Williams <dan.j.williams@intel.com>
This commit is contained in:
Dan Williams 2009-09-08 17:42:50 -07:00
parent f9dd213437
commit 0403e38277
8 changed files with 79 additions and 41 deletions
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3
include/linux/dmaengine.h
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@ -87,6 +87,8 @@ enum dma_transaction_type {
* @DMA_PREP_CONTINUE - indicate to a driver that it is reusing buffers as
* sources that were the result of a previous operation, in the case of a PQ
* operation it continues the calculation with new sources
* @DMA_PREP_FENCE - tell the driver that subsequent operations depend
* on the result of this operation
*/
enum dma_ctrl_flags {
DMA_PREP_INTERRUPT = (1 << 0),
@ -98,6 +100,7 @@ enum dma_ctrl_flags {
DMA_PREP_PQ_DISABLE_P = (1 << 6),
DMA_PREP_PQ_DISABLE_Q = (1 << 7),
DMA_PREP_CONTINUE = (1 << 8),
DMA_PREP_FENCE = (1 << 9),
};
/**