[alsa-devel] Grey noise with HDA Intel PCH

[Julian Wollrath]

Am Thu, 14 Aug 2014 17:11:32 +0200
schrieb Takashi Iwai <tiwai at suse.de>:

> At Thu, 14 Aug 2014 17:04:59 +0200,
> Julian Wollrath wrote:
> > 
> > Am Thu, 14 Aug 2014 16:47:46 +0200
> > schrieb Takashi Iwai <tiwai at suse.de>:
> > 
> > > At Thu, 14 Aug 2014 16:39:14 +0200,
> > > Julian Wollrath wrote:
> > > > 
> > > > Am Thu, 14 Aug 2014 16:09:51 +0200
> > > > schrieb Takashi Iwai <tiwai at suse.de>:
> > > > 
> > > > > At Thu, 14 Aug 2014 16:07:37 +0200,
> > > > > Julian Wollrath wrote:
> > > > > > 
> > > > > > > > > > Simple mixer control 'Mic',0
> > > > > > > > > >   Front Left: Playback 0 [0%] [-34.50dB] [on]
> > > > > > > > > >   Front Right: Playback 0 [0%] [-34.50dB] [on]
> > > > > > > > > 
> > > > > > > > > This plays any noise from the mic input.
> > > > > > > > Turning it off makes no difference since capture is
> > > > > > > > turned off anyway:
> > > > > > > 
> > > > > > > This is a loopback mixer element, it has nothing to do
> > > > > > > with capture stream.
> > > > > > > 
> > > > > > > The likely culprit of the static noises is the signal
> > > > > > > from the analog loopback.  In some cases, you can disable
> > > > > > > the whole loopback via "Loopback Mixing" mixer element on
> > > > > > > the fly.  In some cases, you'd need to disable each mixer
> > > > > > > input (e.g. "Mic Playback Switch"). In some cases (e.g.
> > > > > > > on some Sony and Dell laptops), you'd need to disable the
> > > > > > > complete analog loopback at the initialization.
> > > > > > > 
> > > > > > > The last one can be done via the early patching or sysfs
> > > > > > > reconfiguration, pass "mixer_nid = 0" hint.  See
> > > > > > > HD-Audio.txt for a brief instruction.
> > > > > > Sadly, that did not help.
> > > > > 
> > > > > Give alsa-info.sh output after your change to verify whether
> > > > > you did correctly.
> > > > Here it is, cheers:
> > > 
> > > Thanks.  The setup looks OK, the path is:
> > >   DAC (0x02) -> mixer (0x0c) -> mixer (0x14)
> > > and the mixer mutes the loopback path (index 1).
> > > 
> > > Is it the state where you still hear the static noise?
> > Yes, the alsa-info.sh script was executed, while hearing the static
> > noise.
> 
> OK.  And if you mute "Speaker" or "Headphone", the noise is gone, too,
> right?
No, if I mute "Speaker" (the internal laptop speaker) it is not gone. It
is only gone, if I mute "Master" or have a headphone plugged in and
mute "Headphone" or "Master".

More fascinating, it is not present, if the speaker is not muted and I
disable powersaving via "echo '0' >
'/sys/module/snd_hda_intel/parameters/power_save'" but even then, it is
still present on the headphone.

> > > Also, what if you use the module option for snd-hda-intel
> > > model=nofixup or model=generic?
> > That did not change anything either. Passing the "mixer_nid = 0"
> > hint also did not get rid of the static noise, when loading
> > snd-hda-intel with model=nofixup resp. model=generic.
> 
> Did you reboot with setting the option in /etc/modprobe.d/*?
> Reloading the module might not work for such a problem.
No, I just unloaded every sound-related module and than loaded the
module via "modprobe snd-hda-intel model=..." again.

> In either way, there should be some difference in alsa-info.sh output,
> e.g. more (or less) mixer items with the model option.
The difference is their, all the "Dock ..." entries were missing, when
loading with the model="..." option.

Cheers,
Julian