[alsa-devel] Timer instability

[Takashi Iwai]

At Wed, 25 Feb 2009 18:34:31 +0000,
Clive Messer wrote:
> 
> On Wednesday 25 Feb 2009 18:13:47 Takashi Iwai wrote:
> 
> > > > diff --git a/src/pcm/pcm_hw.c b/src/pcm/pcm_hw.c
> > > > index e9ce092..5211d1c 100644
> > > > --- a/src/pcm/pcm_hw.c
> > > > +++ b/src/pcm/pcm_hw.c
> > > > @@ -131,6 +131,10 @@ struct timespec snd_pcm_hw_fast_tstamp(snd_pcm_t
> > > > *pcm) static int sync_ptr1(snd_pcm_hw_t *hw, unsigned int flags)
> > > >  {
> > > >         int err;
> > > > +       long old_hwptr, new_hwptr;
> > > > +       long old_applptr, new_applptr;
> > > > +       old_hwptr = hw->sync_ptr->s.status.hw_ptr;
> > > > +       old_applptr = hw->sync_ptr->c.control.appl_ptr;
> > > >         hw->sync_ptr->flags = flags;
> > > >         err = ioctl((hw)->fd, SNDRV_PCM_IOCTL_SYNC_PTR,
> > > > (hw)->sync_ptr); if (err < 0) {
> > > > @@ -138,6 +142,11 @@ static int sync_ptr1(snd_pcm_hw_t *hw, unsigned
> > > > int flags) SYSMSG("SNDRV_PCM_IOCTL_SYNC_PTR failed");
> > > >                 return err;
> > > >         }
> > > > +       new_hwptr = hw->sync_ptr->s.status.hw_ptr;
> > > > +       new_applptr = hw->sync_ptr->c.control.appl_ptr;
> > > > +       printf("sync_ptr1: %ld(%ld), %ld(%ld)\n",
> > > > +              new_hwptr, new_hwptr - old_hwptr,
> > > > +              new_applptr, new_applptr - old_applptr);
> > > >         return 0;
> > > >  }
> > > >  
> 
> With sync_ptr I cannot reproduce the very large numbers. Here's a typical log. 
> (Attached).

Hrm, but still an unexpected jump is found.

If you build the driver with CONFIG_SND_PCM_XRUN_DEBUG=y, you must
have /proc/asound/card0/pcm0p/xrun_debug.  Echo 1 to this (as root)
	echo 1 > /proc/asound/card0/pcm0p/xrun_debug
and try the program, see whether any debug message appears.
If any message appears, it means basically an unstable hardware.

Also, the below is a patch I tried to clean up and improve the
handling.  Give it a try (and do echo 1 above for testing).


thanks,

Takashi
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