[alsa-devel] Audio crackles with 4.1-rc1

[Takashi Iwai]

At Thu, 11 Jun 2015 01:12:36 +0300,
Mihai Donțu wrote:
> 
> On Wed, 10 Jun 2015 20:23:01 +0200 Takashi Iwai wrote:
> > From: Takashi Iwai <tiwai at suse.de>
> > Subject: [PATCH] ALSA: hda - Reduce click noise at power up
> > 
> > Some machines suffer from click noises at power up with the recent
> > kernels, and this seems triggered at the power transition and the
> > immediate verb executions.  As a workaround, put a short delay (10ms)
> > right after the D0 transition.
> > 
> > There are a few places that have the same kind of delays, especially
> > in the resume path.  I guess they can be removed (or reduced) after
> > this patch.  But, since the delay is relatively small, let's do it
> > later as a cleanup.
> > 
> > Reported-by: Mihai Donțu <mihai.dontu at gmail.com>
> > Signed-off-by: Takashi Iwai <tiwai at suse.de>
> > ---
> >  sound/pci/hda/hda_codec.c | 3 +++
> >  1 file changed, 3 insertions(+)
> > 
> > diff --git a/sound/pci/hda/hda_codec.c b/sound/pci/hda/hda_codec.c
> > index b7782212dd64..38f5509ee52f 100644
> > --- a/sound/pci/hda/hda_codec.c
> > +++ b/sound/pci/hda/hda_codec.c
> > @@ -3077,6 +3077,9 @@ static unsigned int hda_set_power_state(struct hda_codec *codec,
> >  			break;
> >  	}
> >  
> > +	if (power_state == AC_PWRST_D0)
> > +		msleep(10);
> > +
> >  	return state;
> >  }
> >  
> 
> I take back my previous observations. I was at work and did not have
> access to headphones (one of those days). Now I'm at home, it's 1 AM,
> very quiet, and I notice the following:
> 
>  * on speakers: the click reproduces but with _very_ low amplitude;
>    msleep(100) is unnoticeable, but msleep(10) is, barely;
>  * on headphones: the moment I plug them I hear a loud static sound
>    (like an old, untuned AM radio). If I play something, the static
>    disappears. If I pause, the static returns after ~15s.

OK, then the patch is no-go.  We need a bit deeper analysis.

About the headphone problem: don't you get the same issue with 4.0.x?
Please take alsa-info.sh outputs on both 4.0.x and 4.1 before and
after plugging the headphone, and attach the outputs.
(Run the script with --no-upload option.)


thanks,

Takashi