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

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Date:	Tue, 28 Apr 2015 14:00:17 +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 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.
> 
> Hopefully relevant dmesg output for the device:
> 
> [   23.551075] snd_hda_intel 0000:00:03.0: enabling device (0000 -> 0002)
> [   23.551279] snd_hda_intel 0000:00:03.0: bound 0000:00:02.0 (ops 0xffffffff81891a00)
> [   23.575852] snd_hda_codec_realtek hdaudioC1D0: autoconfig for ALC3226: line_outs=1 (0x16/0x0/0x0/0x0/0x0) type:line
> [   23.575855] snd_hda_codec_realtek hdaudioC1D0:    speaker_outs=1 (0x14/0x0/0x0/0x0/0x0)
> [   23.575857] snd_hda_codec_realtek hdaudioC1D0:    hp_outs=1 (0x15/0x0/0x0/0x0/0x0)
> [   23.575858] snd_hda_codec_realtek hdaudioC1D0:    mono: mono_out=0x0
> [   23.575859] snd_hda_codec_realtek hdaudioC1D0:    inputs:
> [   23.575861] snd_hda_codec_realtek hdaudioC1D0:      Dock Mic=0x19
> [   23.575863] snd_hda_codec_realtek hdaudioC1D0:      Headset Mic=0x1a
> [   23.575870] snd_hda_codec_realtek hdaudioC1D0:      Internal Mic=0x12
> [   23.582324] input: HDA Intel HDMI HDMI/DP,pcm=3 as /devices/pci0000:00/0000:00:03.0/sound/card0/input12
> [   23.582397] input: HDA Intel HDMI HDMI/DP,pcm=7 as /devices/pci0000:00/0000:00:03.0/sound/card0/input13
> [   23.582747] input: HDA Intel HDMI HDMI/DP,pcm=8 as /devices/pci0000:00/0000:00:03.0/sound/card0/input14
> [   23.593267] input: HDA Digital PCBeep as /devices/pci0000:00/0000:00:1b.0/sound/card1/input9
> [   23.594102] input: HDA Intel PCH Dock Mic as /devices/pci0000:00/0000:00:1b.0/sound/card1/input15
> [   23.594268] input: HDA Intel PCH Dock Line Out as /devices/pci0000:00/0000:00:1b.0/sound/card1/input16
> [   23.594346] input: HDA Intel PCH Front Headphone as /devices/pci0000:00/0000:00:1b.0/sound/card1/input17
> 
> I have:
> 
> CONFIG_SND_HDA_POWER_SAVE_DEFAULT=600
> 
> set in my kernel config. There's no dmesg output around the times when
> the crackling is occurring.

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.

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).

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.


Takashi
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