[alsa-devel] [RFC][PATCH] ASoC: OMAP: Fix capture pointer handling for OMAP1510 to work correctly with recent ALSA PCM code

Janusz Krzysztofik jkrzyszt at tis.icnet.pl
Mon Mar 29 14:14:51 CEST 2010

Monday 29 March 2010 10:54:59 Jarkko Nikula napisał(a):
> On Sun, 28 Mar 2010 22:29:29 +0200
> Janusz Krzysztofik <jkrzyszt at tis.icnet.pl> wrote:
> > With recent (2.6.34) chnages in PCM handling, capture stopped working on
> > my OMAP1510 based Amstrad Delta videophone.
> >
> > Using 2.6.34-rc2, I was able to correct the problem in 3 different ways:
> >
> > 1. reverting commit 7b3a177b0d4f92b3431b8dca777313a07533a710,
> > 2. enabling additional jiffies check with
> > 	echo 4 >/proc/asound/card0/pcm0c0/xrun_debug
> > 3. applying the patch below.
> >
> > Since I wasn't able to reproduce the problem on my i686 PC, I guess the
> > problem is probably machine specific.
> >
> > The patch reuses the method for software emulation of missing hardware
> > pointer, already implemented for playback on OMAP1510. It's possible that
> > event if a hardware pointer is available for capture on this machine, its
> > behaviour may be not compatible with what upper layer expects.
> >
> > If you think the problem may be more general and should be solved
> > differently, on a higher level, I can try to work more on it if you give
> > me a hint.
> I don't have anything against this patch as it makes the
> playback/capture code uniform on 1510 but I don't understand why the
> capture broke now if it was working before.
> What I was thinking if there has been always some overruns which were
> not detected on 2.6.34-rc anymore and that caused somehow the capture
> not working on 1510. Could you try does a patch below have any effect?
> http://mailman.alsa-project.org/pipermail/alsa-devel/2010-March/026487.html

Hi Jarrko,

I should have mention that I was already aware of your patch; applied alone, 
it didn't solve the problem for me. However, when configuring ALSA with 
debugging turned off, I have to use both patches, yours and mine, in order to 
get things working.

The most mysterious part of the issue, and most interesting question that I'm 
not able to find an answer myself for, is why the problem can be corrected by 
reverting commit 7b3a177b0d4f92b3431b8dca777313a07533a710.

Jaroslav, I'm CCing you, the author of the "magic" commit, in hope you may be 
able to shed some more light on the issue.


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