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

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Message-ID: <20150630041428.GE3246@localhost>
Date:	Tue, 30 Jun 2015 09:44:28 +0530
From:	Vinod Koul <vinod.koul@...el.com>
To:	Krzysztof Kozłowski <k.kozlowski.k@...il.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

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

-- 
~Vinod

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