Re: [PATCH] ALSA: hda - using POS_FIX_LPIB on Broadwell HDMI Audio

[Takashi Iwai <tiwai@suse.de>]

At Thu, 8 May 2014 06:28:17 +0000,
Yang, Libin wrote:
> 
> Hi Takashi,
> 
> > -----Original Message-----
> > From: Takashi Iwai [mailto:tiwai@suse.de]
> > Sent: Thursday, May 8, 2014 2:20 PM
> > To: Yang, Libin
> > Cc: alsa-devel@alsa-project.org; Lin, Mengdong; Pierre-Louis Bossart
> > Subject: Re: [PATCH] ALSA: hda - using POS_FIX_LPIB on Broadwell HDMI
> > Audio
> > 
> > At Thu, 8 May 2014 06:13:31 +0000,
> > Yang, Libin wrote:
> > >
> > > Hi Takashi,
> > >
> > > > -----Original Message-----
> > > > From: Takashi Iwai [mailto:tiwai@suse.de]
> > > > Sent: Thursday, May 8, 2014 1:51 PM
> > > > To: Yang, Libin
> > > > Cc: alsa-devel@alsa-project.org; Lin, Mengdong; Pierre-Louis Bossart
> > > > Subject: Re: [PATCH] ALSA: hda - using POS_FIX_LPIB on Broadwell
> > > > HDMI Audio
> > > >
> > > > At Thu, 8 May 2014 05:48:04 +0000,
> > > > Yang, Libin wrote:
> > > > >
> > > > > Hi Takashi,
> > > > >
> > > > > I checked the wallclock counter. The counter is OK. But it failed
> > > > > to correct
> > > > the position.
> > > >
> > > > So, how wrong the position buffer is?  Is the problem intermittent?
> > > > Please elaborate more.
> > >
> > > The issue is the position is almost always inaccurate. You will hear there is
> > intermittent noise in the sound. And the sound is played faster than it should
> > be.
> > >
> > > The following message is what I got from dmesg:
> > >
> > > [ 73.278117] snd_hda_intel 0000:00:03.0: IRQ timing workaround is
> > activated for card #0. Suggest a bigger bdl_pos_adj.
> > > [ 73.528575] snd_hda_intel 0000:00:03.0: Unstable LPIB (26240 >=
> > > 24064); disabling LPIB delay counting
> > >
> > > Do you think the print of wallclk and position information in the function
> > azx_position_ok() is useful to you? If yes, I will add debug code to print the
> > info.
> > 
> > It'd better to have the raw values of posbuf, lpib and wallclock for further
> > analysis, yes.
> > 
> > BTW, did you try non-snoop mode via snoop=0 option?
> 
> I haven't tried non-snoop. Do I use `modprobe snd-hda-intel snoop=0` to use non-snoop mode?

Yes.

Takashi