From: Krzysztof Kozlowski Date: Mon, 15 Jun 2015 14:00:09 +0000 (+0900) Subject: dmaengine: pl330: Really fix choppy sound because of wrong residue calculation X-Git-Tag: firefly_0821_release~176^2~1332^2~6 X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=5dd90e5b91e0f5c925b12b132c7cd27538870256;p=firefly-linux-kernel-4.4.55.git dmaengine: pl330: Really fix choppy sound because of wrong residue calculation When pl330 driver was used during sound playback, after some time or after a number of plays the sound became choppy or totally noisy. For example on Odroid XU3 board the first four executions of aplay with small WAVE worked fine, but fifth was unrecognizable with errors: $ aplay /usr/share/sounds/alsa/Front_Right.wava underrun!!! (at least 0.095 ms long) Issue was caused by wrong residue reported by pl330 driver to pcm_dmaengine for its cyclic dma transfers. The pl330_tx_status(), residue reporting function, used a "last" flag in a descriptor to indicate that there is no more data to send. The pl330_tx_submit() iterated over descriptors trying to remove this flag from them and then mark last descriptor as "last". However when iterating it actually removed the flag not from descriptors but always from last of it (and then reset it). Thus effectively once some descriptor was marked as last, then it stayed like this forever causing residue to be reported too low. Signed-off-by: Krzysztof Kozlowski Fixes: aee4d1fac887 ("dmaengine: pl330: improve pl330_tx_status() function") Cc: Reported-by: gabriel@unseen.is Suggested-by: Marek Szyprowski Tested-by: Lars-Peter Clausen Signed-off-by: Vinod Koul --- diff --git a/drivers/dma/pl330.c b/drivers/dma/pl330.c index c535cd059724..ecab4ea059b4 100644 --- a/drivers/dma/pl330.c +++ b/drivers/dma/pl330.c @@ -2328,7 +2328,7 @@ static dma_cookie_t pl330_tx_submit(struct dma_async_tx_descriptor *tx) desc->txd.callback = last->txd.callback; desc->txd.callback_param = last->txd.callback_param; } - last->last = false; + desc->last = false; dma_cookie_assign(&desc->txd);