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dmaengine: dma-jz4780: Further residue status fix 

Func jz4780_dma_desc_residue() expects the index to the next hw
descriptor as its last parameter. Caller func jz4780_dma_tx_status(),
however, applied modulus before passing it. When the current hw
descriptor was last in the list, the index passed became zero.

The resulting excess of reported residue especially caused problems
with cyclic DMA transfer clients, i.e. ALSA AIC audio output, which
rely on this for determining current DMA location within buffer.

Combined with the recent and related residue-reporting fixes, spurious
ALSA audio underruns on jz4770 hardware are now fixed.

Signed-off-by: Daniel Silsby <dansilsby@gmail.com>
Signed-off-by: Paul Cercueil <paul@crapouillou.net>
Tested-by: Mathieu Malaterre <malat@debian.org>
Signed-off-by: Vinod Koul <vkoul@kernel.org>
This commit is contained in:
Daniel Silsby 2018-08-29 23:32:56 +02:00 committed by Vinod Koul
parent 9e4e3a4c00
commit 83ef4fb755
1 changed files with 1 additions and 1 deletions
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2
drivers/dma/dma-jz4780.c
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@ -653,7 +653,7 @@ static enum dma_status jz4780_dma_tx_status(struct dma_chan *chan,
to_jz4780_dma_desc(vdesc), 0);
} else if (cookie == jzchan->desc->vdesc.tx.cookie) {
txstate->residue = jz4780_dma_desc_residue(jzchan, jzchan->desc,
(jzchan->curr_hwdesc + 1) % jzchan->desc->count);
jzchan->curr_hwdesc + 1);
} else
txstate->residue = 0;