[alsa-devel] [RFC PATCH] ALSA: hda - suspend codecs in parallel

[Lin, Mengdong]

Hi Takashi,

> -----Original Message-----
> From: Takashi Iwai [mailto:tiwai at suse.de]
> Sent: Monday, November 25, 2013 6:51 PM

> >  int snd_hda_suspend(struct hda_bus *bus)  {
> >  	struct hda_codec *codec;
> > +	unsigned int mask = 0;
> >
> >  	list_for_each_entry(codec, &bus->codec_list, list) {
> >  		cancel_delayed_work_sync(&codec->jackpoll_work);
> > -		if (hda_codec_is_power_on(codec))
> > -			hda_call_codec_suspend(codec, false);
> > +		if (hda_codec_is_power_on(codec)) {
> > +			if (codec->epss || bus->num_codecs == 1)
> > +				hda_call_codec_suspend(codec, false);
> 
> What's the reason for codec->epss check exceptionally?

Check on codec->epss should be removed here. It's better to always parallel if there are multiple codecs.
I had thought codec with EPSS support can change power state quickly and so we can tolerate not paralleling. 

> > +			else {
> > +				mask |= 1 << codec->addr;
> > +				queue_work(codec->pm_wq, &codec->pm_work);
> > +			}
> > +		}
> > +	}
> > +
> > +	list_for_each_entry(codec, &bus->codec_list, list) {
> > +		if (mask & (1 << codec->addr))
> > +			flush_work(&codec->pm_work);
> > +
> >  	}
> 
> I thought that the recent workqueue is performed asynchronously as
> default (unless an ordered workqueue is used), so it should be enough to
> have a single workqueue in the bus, and flush it.

If using the single work queue in the bus, I observe that the codecs are suspended one after one, not in parallel. 

Thanks
Mengdong