[alsa-devel] [PATCH 2/3] ALSA: hda - WAKEEN feature enabling for runtime pm

[Takashi Iwai]

At Wed, 24 Jul 2013 13:40:15 +0000,
Wang, Xingchao wrote:
> 
> 
> 
> > -----Original Message-----
> > From: Takashi Iwai [mailto:tiwai at suse.de]
> > Sent: Wednesday, July 24, 2013 6:49 PM
> > To: Wang, Xingchao
> > Cc: David Henningsson; Wang Xingchao; alsa-devel at alsa-project.org;
> > Girdwood, Liam R
> > Subject: Re: [PATCH 2/3] ALSA: hda - WAKEEN feature enabling for runtime pm
> > 
> > At Tue, 23 Jul 2013 08:09:02 +0000,
> > Wang, Xingchao wrote:
> > >
> > > > >
> > > > > Signed-off-by: Wang Xingchao <xingchao.wang at linux.intel.com>
> > > > > ---
> > > > >   sound/pci/hda/hda_intel.c | 25 +++++++++++++++++++++++++
> > > > >   1 file changed, 25 insertions(+)
> > > > >
> > > > > diff --git a/sound/pci/hda/hda_intel.c b/sound/pci/hda/hda_intel.c
> > > > > index 8860dd5..a7ac7fd 100644
> > > > > --- a/sound/pci/hda/hda_intel.c
> > > > > +++ b/sound/pci/hda/hda_intel.c
> > > > > @@ -2970,6 +2970,11 @@ static int azx_runtime_suspend(struct
> > > > > device
> > > > *dev)
> > > > >   {
> > > > >   	struct snd_card *card = dev_get_drvdata(dev);
> > > > >   	struct azx *chip = card->private_data;
> > > > > +	int status;
> > > > > +
> > > > > +	/* enable controller wake up event */
> > > > > +	azx_writew(chip, WAKEEN, azx_readw(chip, WAKEEN) |
> > > > > +		  STATESTS_INT_MASK);
> > > > >
> > > > >   	azx_stop_chip(chip);
> > > > >   	azx_enter_link_reset(chip);
> > > > > @@ -2983,11 +2988,31 @@ static int azx_runtime_resume(struct
> > > > > device
> > > > *dev)
> > > > >   {
> > > > >   	struct snd_card *card = dev_get_drvdata(dev);
> > > > >   	struct azx *chip = card->private_data;
> > > > > +	struct hda_bus *bus;
> > > > > +	struct hda_codec *codec;
> > > > > +	int status;
> > > > >
> > > > >   	if (chip->driver_caps & AZX_DCAPS_I915_POWERWELL)
> > > > >   		hda_display_power(true);
> > > > > +
> > > > > +	/* Read STATESTS before controller reset */
> > > > > +	status = azx_readw(chip, STATESTS);
> > > > > +
> > > > >   	azx_init_pci(chip);
> > > > >   	azx_init_chip(chip, 1);
> > > > > +
> > > > > +	bus = chip->bus;
> > > > > +	if (status && bus) {
> > > > > +		list_for_each_entry(codec, &bus->codec_list, list)
> > > > > +			if (status & (1 << codec->addr))
> > > > > +				queue_delayed_work(codec->bus->workq,
> > > > > +						   &codec->jackpoll_work,
> > > > codec->jackpoll_interval);
> > > >
> > > > Is there a reason you want to move the jack detection to a delayed
> > > > work, i e, why can't we just call:
> > > >
> > > >   	snd_hda_jack_set_dirty_all(codec);
> > > >   	snd_hda_jack_poll_all(codec);
> > > >
> > > > ...from here?
> > >
> > > In fact it doesnot work for me, It will again call runtime_resume() and caused
> > dead loop.
> > 
> > It means that the power refcount is messed up by this way.
> > 
> > When a verb is executed, the codec goes to a full resume mode, which turns up
> > the controller, eventually calling azx_power_notify().
> > In azx_power_notify(), pm_runtime_{get|put}_sync() is called accordingly,
> > which again goes to runtime resume.  A quick fix would be to add a flag or
> > something to avoid reentrace.
> > 
> > But, calling the jackpoll in the resume is basically superfluous.
> > As already mentioned, issuing a verb itself triggers the full resume, and this
> > already includes the update of the whole jack status.
> > Thus, executing jackpoll at that place means to perform the jack polling twice.
> > 
> > In other words, what's we need to achieve is just to call
> > snd_hda_resume() appropriately in the runtime resume case.
> > Of course, this will need more fixes for avoiding reentrance, etc.
> 
> Thanks for clarification on the internal logic, Takashi.
> I will modify the patch and do some test tormorrow when I'm at office.

Well, it might be that reusing the jackpoll would be simpler in the
end.  But, even if it's so, give a better description in the first
patch.  It doesn't clarify _why_ it's needed.  And need to clarify
that it doesn't give any ill-effect, too.

(And actually there will be an impact by that change; patch_via.c
 changes the jackpoll_interval dynamically, and the work will be still
 pending with jackpoll_interval=0.  This code should be modified
 before your patch, i.e. clearing the jackpoll_interval before
 cancel_work_sync().)


> > But, it leads to another question: do we need a full resume just for jack
> > detection and user-space notification?  Just reading the pin detect state
> > should be able to run even in D3 (for chips that are capable of it), and the
> > notification itself doesn't need any audio hardware action.
> 
> It will not harm the basic audio playback function. In case audio controller is in runtime suspend mode,
> Jack detection may not be detected, but when user start to play audio, It will wake up system and
> Jack event will be updated then. So user will not hear sound from speaker in such case.
> 
> The exception is user space did not get real-time jack event, it will confuse user.

Yes, and doing the full resume takes time and power.  So, if it's
avoidable, it'd be better to avoid it.  But, again, it depends on how
complex it'd become.


Takashi