linux-kernel - Re: [PATCH bugfix v3.4] ALSA: hda - fix "silence after S3" regression

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Date:	Tue, 08 May 2012 17:38:45 +0400
From:	Konstantin Khlebnikov <khlebnikov@...nvz.org>
To:	Takashi Iwai <tiwai@...e.de>
CC:	"alsa-devel@...a-project.org" <alsa-devel@...a-project.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	David Henningsson <david.henningsson@...onical.com>,
	Jaroslav Kysela <perex@...ex.cz>
Subject: Re: [PATCH bugfix v3.4] ALSA: hda - fix "silence after S3" regression

Takashi Iwai wrote:
> At Tue, 08 May 2012 17:08:10 +0400,
> Konstantin Khlebnikov wrote:
>>
>> This fixes regression in shd-hda-codec after 785f857d1cb0856b612b46a0545b74aa2
>> ("ALSA: hda - Set codec to D3 forcibly even if not used")
>>
>> hda_set_power_state() call must be explicitly protected against recursive
>> snd_hda_power_up/down() calls, otherwise it accidentally switches device into
>> D0 right before suspend. As result after resume sound device stays in D3 state
>> and does not works because driver believes that the device is on already.
>>
>> Signed-off-by: Konstantin Khlebnikov<khlebnikov@...nvz.org>
>
> Hrm, does this really fix your problem?  The path is called only
> during the suspend.  Then, in the resume path, the codec is all
> powered up anyway.

This fixes my problem: during suspend hda_set_power_state() calls snd_hda_power_up()
it set codec->power_on = 1 and switches device into D0. At S3 resume codec->power_on == 1
but all devices actually in D3 state. As result on resume path device stays in D3,
but after one power-save cycle all works again.

>
> If the race between the leftover power-save work is really a culprit,
> the fix would be just calling cancel_delayed_work_sync() before
> that point...

Race was always there, my problem was caused by commit which mentioned above.

Whole this code is very racy, someone needs to fix it.

>
>
> thanks,
>
> Takashi
>
>> ---
>>   sound/pci/hda/hda_codec.c |    6 +++++-
>>   1 file changed, 5 insertions(+), 1 deletion(-)
>>
>> diff --git a/sound/pci/hda/hda_codec.c b/sound/pci/hda/hda_codec.c
>> index 7a8fcc4..a0ea9d6 100644
>> --- a/sound/pci/hda/hda_codec.c
>> +++ b/sound/pci/hda/hda_codec.c
>> @@ -5444,10 +5444,14 @@ int snd_hda_suspend(struct hda_bus *bus)
>>   	list_for_each_entry(codec,&bus->codec_list, list) {
>>   		if (hda_codec_is_power_on(codec))
>>   			hda_call_codec_suspend(codec);
>> -		else /* forcibly change the power to D3 even if not used */
>> +		else {
>> +			/* forcibly change the power to D3 even if not used */
>> +			codec->power_transition = 1;
>>   			hda_set_power_state(codec,
>>   					    codec->afg ? codec->afg : codec->mfg,
>>   					    AC_PWRST_D3);
>> +			codec->power_transition = 0;
>> +		}
>>   		if (codec->patch_ops.post_suspend)
>>   			codec->patch_ops.post_suspend(codec);
>>   	}
>>
> --
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