[alsa-devel] [PATCH] ALSA: hda - More pop noise fixes for Dell XPS 13 9333

[Takashi Iwai]

At Fri, 08 Aug 2014 17:01:44 +0200,
Gabriele Mazzotta wrote:
> 
> On Friday 08 August 2014 12:13:38 you wrote:
> > At Fri, 08 Aug 2014 10:49:25 +0200,
> > Gabriele Mazzotta wrote:
> > > 
> > > On Friday 08 August 2014 08:11:18 Takashi Iwai wrote:
> > > > At Thu, 07 Aug 2014 18:35:39 +0200,
> > > > Gabriele Mazzotta wrote:
> > > > > 
> > > > > On init, mic-in is always set as input source, indipendently on what
> > > > > is plugged in. Since setting/unsetting mic-in as input source causes
> > > > > a pop noise, make sure the internal microphone is selected as input
> > > > > source on boot.
> > > > > 
> > > > > On shutdown, make sure the codec is not suspended as that would cause
> > > > > a pop noise.
> > > > > 
> > > > > Signed-off-by: Gabriele Mazzotta <gabriele.mzt at gmail.com>
> > > > > ---
> > > > >  sound/pci/hda/hda_codec.c     |  2 ++
> > > > >  sound/pci/hda/hda_codec.h     |  1 +
> > > > >  sound/pci/hda/patch_realtek.c | 12 ++++++++++++
> > > > >  3 files changed, 15 insertions(+)
> > > > > 
> > > > > diff --git a/sound/pci/hda/hda_codec.c b/sound/pci/hda/hda_codec.c
> > > > > index 4c20277..92d8292 100644
> > > > > --- a/sound/pci/hda/hda_codec.c
> > > > > +++ b/sound/pci/hda/hda_codec.c
> > > > > @@ -5348,6 +5348,8 @@ void snd_hda_bus_reboot_notify(struct hda_bus *bus)
> > > > >  	if (!bus)
> > > > >  		return;
> > > > >  	list_for_each_entry(codec, &bus->codec_list, list) {
> > > > > +		if (codec->resume_at_reboot)
> > > > > +			hda_call_codec_resume(codec);
> > > > 
> > > > Do you really need the resume at reboot?  I thought the codec needs
> > > > power down at reboot, i.e. rather it needs suspend.
> > > 
> > > Yes, the pop noise happens if it's suspended.
> > 
> > Then the patch is wrong in anyway.  You cannot call it
> > unconditionally.  The codec might be still active, and calling resume
> > in that state does re-initialize the whole things doubly.
> 
> Now I see that it's wrong. In addition, I guess it also breaks the build 
> when CONFIG_PM is not set.
> 
> > > Now that I payed more attention, the pop noise happens only when 
> > > rebooting the laptop and not when powering it down.
> > > Also, the noise is heard quite late, I think the kernel is no longer 
> > > running when I hear it.
> > > I will try to better understand what is actually happening and why
> > > resuming prevents the noise.
> > 
> > If so, it might be BIOS causes the noise by re-initializing the
> > codec.
> 
> It seems that if 0x15 (Headphone playback switch) is in D0, the pop noise 
> cannot be heard.
> I tried to see using powertop whether it's worth making the current code more 
> complex and force nid 0x15 in D0 only at reboot or not and I couldn't notice 
> any major difference. Between 0x02, 0x15 and AFG only the last is causing a 
> noticeable difference in the power consumption.
> 
> That said, I would simply add 0x15 to alc_power_filter_xps13(). I will send the 
> patches soon.

Thanks, it's a good catch.


Takashi