From mboxrd@z Thu Jan  1 00:00:00 1970
From: Takashi Iwai <tiwai@suse.de>
Subject: Re: multi-channel playback regression
Date: Thu, 23 Jul 2009 10:36:36 +0200
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To: Wu Fengguang <fengguang.wu@intel.com>
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At Thu, 23 Jul 2009 16:33:08 +0800,
Wu Fengguang wrote:
> 
> On Thu, Jul 23, 2009 at 04:15:59PM +0800, Takashi Iwai wrote:
> > At Thu, 23 Jul 2009 15:56:20 +0800,
> > Wu Fengguang wrote:
> > > 
> > > On Thu, Jul 23, 2009 at 03:30:54PM +0800, Takashi Iwai wrote:
> > > > At Thu, 23 Jul 2009 15:22:53 +0800,
> > > > Wu Fengguang wrote:
> > > > > 
> > > > > On Thu, Jul 23, 2009 at 03:01:21PM +0800, Takashi Iwai wrote:
> > > > > > At Thu, 23 Jul 2009 14:53:45 +0800,
> > > > > > Wu Fengguang wrote:
> > > > > > > 
> > > > > > > Hi Takashi,
> > > > > > > 
> > > > > > > When doing multi-channel playback tests on IbexPeak, I found that the
> > > > > > > following patch makes the playback enter an infinite loop, repeatedly
> > > > > > > playing a range of ~0.5s audio content. (Seems that some buffer
> > > > > > > pointer can never advance.)
> > > > > > 
> > > > > > Could you set 1 to /proc/asound/card0/pcm0p/xrun_debug and give the
> > > > > > messages?  Also, please show /proc/.../pcm0p/sub0/hw_params, too.
> > > > > > 
> > > > > > The change affects only the code path for the problematic hardware
> > > > > > that reports wrong DMA position.  So, if this change regresses, it
> > > > > > means that the device has been already problematic from the
> > > > > > beginning...
> > > > > 
> > > > > I caught some messages:
> > > > 
> > > > Is this with the patched (as is on sound git tree) kernel?
> > > 
> > > Yes, it's unmodified latest git tree.
> > > 
> > > > What if changing from #if 1 to #if 0?
> > > 
> > > This makes 8-channel playback work again.
> > 
> > OK, then could you apply the patch below, and do
> > "echo 9 > /proc/../xrun_debug", then gather the messages with both
> > #if 1 and #if 0?  This will record the each snd_pcm_period_elpased()
> > so beware that you may get flood of messages.
> 
> OK, but for now this box is doing something else that cannot interrupted.
> So I'll try the patch some time later. Sorry.

Sure, no problem.

Meanwhile, I'm thinking applying the debug-print patch now.
Any objection?


Takashi