linux-kernel - Re: Audio crackles with 4.1-rc1

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Date:	Tue, 28 Apr 2015 16:43:00 +0200
From:	Takashi Iwai <tiwai@...e.de>
To:	Jonathan McDowell <noodles@...th.li>
Cc:	alsa-devel@...a-project.org, linux-kernel@...r.kernel.org
Subject: Re: Audio crackles with 4.1-rc1

At Tue, 28 Apr 2015 15:05:20 +0200,
Takashi Iwai wrote:
> 
> At Tue, 28 Apr 2015 13:35:18 +0100,
> Jonathan McDowell wrote:
> > 
> > On Tue, Apr 28, 2015 at 02:00:17PM +0200, Takashi Iwai wrote:
> > > At Tue, 28 Apr 2015 12:21:57 +0100,
> > > Jonathan McDowell wrote:
> > > > 
> > > > Having upgraded to 4.1-rc1 from 4.0 I'm now hearing audio crackles at
> > > > regular intervals. I'm fairly sure this is due to the HDA power save as
> > > > once audio is playing things are fine, it's just when starting to play
> > > > audio that I hear the crackle.
> > > > 
> > > > System is a Dell Latitude E7240. I haven't tried a bisect yet but will
> > > > attempt to find some time to do so in the next few days. It looks like
> > > > there have been some changes in sound/hda/ between 4.0 + 4.1-rc1 so I'll
> > > > concentrate on those first.
> > > > 
> > > There are lots of code changes and enhancements wrt power saving in
> > > 4.1, and bisection won't help so much, I'm afraid.
> > > 
> > > First off, check the device status while you hear crackles.
> > > Is the codec in runtime suspend (aka power save)?  This can be seen in
> > > /sys/bus/hdaudio/devices/*/power/runtime_status.  Then check the
> > > runtime status of the controller, too, found in
> > > /sys/class/sound/card?/device/power/runtime_status.
> > 
> > The cracking is definitely happening with the transition from suspended
> > to active:
> > 
> > /sys/class/sound/card0/device/power/runtime_status:suspended
> > /sys/class/sound/card1/device/power/runtime_status:active
> > /sys/bus/hdaudio/devices/hdaudioC0D0/power/runtime_status:suspended
> > /sys/bus/hdaudio/devices/hdaudioC1D0/power/runtime_status:active
> > 
> > card1 + C1D0 were suspended, I hit delete in a terminal to force a
> > terminal bell, got the crackle and the state changed to active as above.
> 
> Ah, so it's a click noise that happens only once per runtime PM
> transition?  I thought it were constant crackling noises from your
> description ("regular intervals").
> 
> In anyway, please give alsa-info.sh output on both 4.0 and 4.1.

Also, does the click noise occur only at powering up, and not at
powering down?


Takashi
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