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

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Date:	Tue, 30 Jun 2015 13:51:13 +0900
From:	Krzysztof Kozłowski <k.kozlowski.k@...il.com>
To:	Vinod Koul <vinod.koul@...el.com>
Cc:	gabriel@...een.is, Marek Szyprowski <m.szyprowski@...sung.com>,
	dmaengine@...r.kernel.org, Dan Williams <dan.j.williams@...el.com>,
	stable@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] dmaengine: pl330: Really fix choppy sound because of
 wrong residue calculation

2015-06-30 13:14 GMT+09:00 Vinod Koul <vinod.koul@...el.com>:
> On Mon, Jun 22, 2015 at 11:14:42AM +0900, Krzysztof Kozłowski wrote:
>> 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.
>
> So is there a word on  what finally fixes this

This fixes sound issue on my Odroid XU3 board, which is good. My board
has the same audio codec and DMA driver as the board used by Gabriel
so there is high chance that his issue is also fixed.

However it is sad that I did not receive any reviews or tests from
anyone, apparently no one cares enough about it :) .

Anyway the patch was also merged to Tizen kernel tree:
https://review.tizen.org/git/?p=platform/kernel/linux-exynos.git;a=shortlog;h=refs/heads/tizen
https://review.tizen.org/git/?p=platform/kernel/linux-exynos.git;a=commit;h=41dec9884a82443da1b7814ae42efe65895ff3af

Best regards,
Krzysztof
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