linux-kernel - Re: [PATCH] dmaengine: pl330: Really fix choppy sound because of wrong residue calculation

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Date:	Mon, 22 Jun 2015 11:14:42 +0900
From:	Krzysztof Kozłowski <k.kozlowski.k@...il.com>
To:	gabriel@...een.is
Cc:	Marek Szyprowski <m.szyprowski@...sung.com>,
	dmaengine@...r.kernel.org, Dan Williams <dan.j.williams@...el.com>,
	Krzysztof Kozlowski <k.kozlowski.k@...il.com>,
	stable@...r.kernel.org, Vinod Koul <vinod.koul@...el.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] dmaengine: pl330: Really fix choppy sound because of
 wrong residue calculation

2015-06-15 23:00 GMT+09:00 Krzysztof Kozlowski <k.kozlowski.k@...il.com>:
> 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 <k.kozlowski.k@...il.com>
> Fixes: aee4d1fac887 ("dmaengine: pl330: improve pl330_tx_status() function")
> Cc: <stable@...r.kernel.org>
> Reported-by: gabriel@...een.is
> Suggested-by: Marek Szyprowski <m.szyprowski@...sung.com>

Gabriel, could you give this patch a try? It helped for my Odroid XU3,
which has the same audio codec. Nevertheless it would be great to hear
that it solves the initial bug report.

Best regards,
Krzysztof
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