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

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Message-ID: <20150428123518.GU10148@earth.li>
Date:	Tue, 28 Apr 2015 13:35:18 +0100
From:	Jonathan McDowell <noodles@...th.li>
To:	Takashi Iwai <tiwai@...e.de>
Cc:	alsa-devel@...a-project.org, linux-kernel@...r.kernel.org
Subject: Re: Audio crackles with 4.1-rc1

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.

> And, take alsa-info.sh output snapshot while the noise.  Run the
> script with --no-upload option and attach the output file.  Also, take
> alsa-info.sh output on 4.0 kernel for comparison, too.  At best, take
> a snapshot in the similar situation (in power save, etc).

Unfortunately the crackle is really very brief so it's difficult to
catch it in the act. I've attached the alsa-info.sh output from when
the above is reporting suspended and then when it's reporting active.

> The possibly affecting change was the support of widget power saving.
> For disabling it, try to comment out the line
> 	codec->power_save_node = 1;
> in patch_alc269() in sound/pci/hda/patch_realtek.c.

I'll try this out but it's probably going to be at least tomorrow before
I have time.

J.

-- 
                                            xmpp:noodles@...th.li
101 things you can't have too much of : 10
                                            - CDs.

View attachment "alsa-info.txt.suspended" of type "text/plain" (40238 bytes)

View attachment "alsa-info.txt.active" of type "text/plain" (40239 bytes)