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dmaengine: Clarify cyclic transfer residue documentation

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The current documentation for the residue reported in a cyclic transfer
case mentions that the reported residue should be relative to the current
period only. However the definition of DMA_RESIDUE_GRANULARITY_SEGMENT
specifies that the residue should be updated after each period for
a cyclic transfer, which is in direct contradiction.

Moreover the pcm_dmaengine common code uses the residue relative to
the whole cyclic buffer size, not one period.

Correct the residue-related documentation to reflect this.

Signed-off-by: Paul Kocialkowski <paul.kocialkowski@bootlin.com>
Link: https://lore.kernel.org/r/20220331134114.703782-1-paul.kocialkowski@bootlin.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>
This commit is contained in:
Paul Kocialkowski 2022-03-31 15:41:14 +02:00 committed by Vinod Koul
parent ec834f1cc7
commit 1f854536a8
1 changed files with 1 additions and 1 deletions
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2
Documentation/driver-api/dmaengine/provider.rst
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@ -457,7 +457,7 @@ supported.
- Should use dma_set_residue to report it
- In the case of a cyclic transfer, it should only take into
account the current period.
account the total size of the cyclic buffer.
- Should return DMA_OUT_OF_ORDER if the device does not support in order
completion and is completing the operation out of order.