linux-kernel - Re: [PATCH 09/18] ASoC: Samsung: Do not queue cyclic buffers multiple times

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Date:	Wed, 28 Aug 2013 10:23:34 +0200
From:	Tomasz Figa <tomasz.figa@...il.com>
To:	Linus Walleij <linus.walleij@...aro.org>,
	Mark Brown <broonie@...nel.org>
Cc:	linux-samsung-soc <linux-samsung-soc@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"alsa-devel@...a-project.org" <alsa-devel@...a-project.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	linux-spi@...r.kernel.org, Dan Williams <djbw@...com>,
	Jaroslav Kysela <perex@...ex.cz>,
	Kukjin Kim <kgene.kim@...sung.com>,
	Liam Girdwood <lgirdwood@...il.com>,
	Mike Turquette <mturquette@...aro.org>,
	Padmavathi Venna <padma.v@...sung.com>,
	Russell King <linux@....linux.org.uk>,
	Sangbeom Kim <sbkim73@...sung.com>,
	Takashi Iwai <tiwai@...e.de>, Vinod Koul <vinod.koul@...el.com>
Subject: Re: [PATCH 09/18] ASoC: Samsung: Do not queue cyclic buffers multiple times

On Wednesday 28 of August 2013 09:06:27 Linus Walleij wrote:
> On Sun, Aug 11, 2013 at 7:59 PM, Tomasz Figa <tomasz.figa@...il.com> 
wrote:
> > The legacy S3C-DMA API required every period of a cyclic buffer to be
> > queued separately. After conversion of Samsung ASoC to Samsung DMA
> > wrappers somebody made an assumption that the same is needed for DMA
> > engine API, which is not true.
> > 
> > In effect, Samsung ASoC DMA code was queuing the whole cyclic buffer
> > 
> > multiple times with a shift of one period per iteration, leading to:
> >   a) severe memory waste - up to 13x times more DMA transfer
> >   descriptors
> >   
> >      are allocated than needed,
> >   
> >   b) possible memory corruption, because further cyclic buffers were
> >   out
> >   
> >      of the original buffers, due to the offset.
> > 
> > This patch fixes this problem by making the legacy S3C-DMA API use the
> > same semantics as DMA engine (the whole cyclic buffer is enqueued at
> > once) and modifying users of Samsung DMA wrappers in cyclic mode to
> > behave appropriately.
> > 
> > Signed-off-by: Tomasz Figa <tomasz.figa@...il.com>
> > Acked-by: Linus Walleij <linus.walleij@...aro.org>
> 
> If patch 1 thru 9 are uncontroversial now, maybe Vinod can apply
> these for v3.12 so we can get less noise and risk of collissions
> in the next merge window?
> 
> Just an idea.

That would be nice, leaving only Samsung-specific patches for the next 
merge window.

(That would be patches 1 to 8, though, as 9 is a patch for ASoC that could 
be picked up by Mark Brown independently.)

Best regards,
Tomasz

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