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

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Message-ID: <s5hd22l7dgo.wl-tiwai@suse.de>
Date:	Thu, 30 Apr 2015 19:06:31 +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 Thu, 30 Apr 2015 16:01:31 +0100,
Jonathan McDowell wrote:
> 
> On Wed, Apr 29, 2015 at 01:54:57PM +0200, Takashi Iwai wrote:
> > At Wed, 29 Apr 2015 12:28:59 +0100,
> > Jonathan McDowell wrote:
> > > 
> > > On Tue, Apr 28, 2015 at 04:43:00PM +0200, Takashi Iwai wrote:
> > > > 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?
> > > 
> > > The click is only on the transition from suspended to active; not
> > > constantly during playback and not when transitioning from active to
> > > suspended. It doesn't appear 4.0 is doing the suspending at all; there
> > > are no /sys/bus/hdaudio/devices/*/power/runtime_status files and the
> > > card runtime_status is always active. alsa-info for 4.0 + 4.1-rc1
> > > attached.
> > 
> > OK, thanks for clarification.
> > 
> > One patch you can try (with or without power_save_node disablement) is
> > below, it squashes the verb sequences at (runtime) PM resume as we did
> > for 4.0.  Let me know if this changes the behavior.
> 
> Patch alone has no effect. Patch with power_save_node disablement solves
> the problem. Didn't try power_save_node disablement without the patch.

Then please confirm that only power_save_node disablement suffices.
This can be considered as the least change that can be put to 4.1-rc
if no better fix is found.


thanks,

Takashi
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