[alsa-devel] Invalid PCM pointer with CMI8738 and pcm.c buffer underuns

Takashi Iwai tiwai at suse.de
Tue Apr 29 08:04:31 CEST 2014

At Mon, 28 Apr 2014 21:28:42 +0000 (UTC),
Andoru wrote:
> [Continued from here:
> http://thread.gmane.org/gmane.linux.alsa.devel/122028/focus=122354 ]
> > It's way too old.  Better to build the latest kernel.
> The latest kernel available for my distro, or the latest kernel available
> "from Linus"? I've already tried the former.

The latter.

> > You need to figure out the condition reproducing the issue.
> For all I know (I'm not that knowledgeable on those things, mind you) this
> happens completely at random. There hasn't been any pattern when the PC
> would become unusable, and the OS unresponsive.

If it's completely random, it's a hardware problem, and impossible to
fix properly.  If there is some condition (i.e. happens only when
using this period size and buffer size, etc), then we have a chance to
fix.  You have to figure out it by yourself.  Note that the condition
doesn't mean only the timing.  It means the audio setup you're using,

> > For example, application may apply some strange buffer size and period
> > size the hardware chip doesn't like. If so, changing the buffer size
> > and/or period size may reduce the problem.
> I'm not aware of any feature to change the buffer size in any of the
> programs that cause the lock-ups.

If so, try another program (or better to write a test case by
yourself) to reproduce the problem more easily and allow you to adjust
the parameters to figure out the condition.

> > Meanwhile, you can try the patch below, too, which aligns the period
> That patch is for kernel sources or for the above snapshots I mentioned? Or
> perhaps there are more recent ALSA source codes?

It should be applicable to most of existing versions.


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