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

[Konstantin Khlebnikov]

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@xxxxxxxxxx>
>
> 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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