Re: HDA, power saving and recording

[Takashi Iwai <tiwai@suse.de>]

On Fri, 12 May 2023 14:00:54 +0200,
Amadeusz Sławiński wrote:
> 
> On 5/12/2023 1:33 PM, Takashi Iwai wrote:
> > On Fri, 12 May 2023 13:23:49 +0200,
> > Takashi Iwai wrote:
> >> 
> >> On Thu, 11 May 2023 19:20:17 +0200,
> >> Amadeusz Sławiński wrote:
> >>> 
> >>> On 5/11/2023 5:58 PM, Takashi Iwai wrote:
> >>>> On Thu, 11 May 2023 17:31:37 +0200,
> >>>> Amadeusz Sławiński wrote:
> >>>>> 
> >>>>> On 5/10/2023 2:21 PM, Takashi Iwai wrote:
> >>>>>> On Tue, 09 May 2023 12:10:06 +0200,
> >>>>>> Amadeusz Sławiński wrote:
> >>>>> Then capture stream starts and seems to assume that
> >>>>> registers were already set, so it doesn't write them to hw.
> >>>> 
> >>>> ... it seems this didn't happen, and that's the inconsistency.
> >>>> 
> >>>> So the further question is:
> >>>> At the point just before you start recording, is the codec in runtime
> >>>> suspended?  Or it's running?
> >>>> 
> >>>> If it's runtime-suspended, snd_hda_regmap_sync() must be called from
> >>>> alc269_resume() via runtime-resume, and this must write out the
> >>>> cached values.  Then the bug can be along with that line.
> >>>> 
> >>>> Or if it's running, it means that the previous check of
> >>>> snd_hdac_keep_power_up() was bogus (or racy).
> >>>> 
> >>> 
> >>> Well, it is in... let's call it semi powered state. When snd_hda_intel
> >>> driver is loaded with power_save=X option it sets timeout to X seconds
> >>> and problem only happens when I start the stream before those X
> >>> seconds pass and it runs first runtime suspend. After it suspends it
> >>> then uses standard pm_runtime_resume and works correctly. That's why
> >>> the pm_runtime_force_suspend(&codec->core.dev);  mentioned in first
> >>> email in thread "fixes" the problem, as it forces it to be instantly
> >>> suspended instead of waiting for timeout and then later normal
> >>> resume-play/record-suspend flow can be followed.
> >> 
> >> Hm, then maybe it's a bad idea to rely on the usage count there.
> >> Even if the usage is 0, the device can be still active, and the update
> >> can be missed.
> >> 
> >> How about the patch like below?
> > 
> > Scratch that, it returns a wrong value.
> > A simpler version like below works instead?
> > 
> 
> Yes it was broken, arecord didn't even start capturing ;)
> 
> > 
> > Takashi
> > 
> > --- a/sound/hda/hdac_device.c
> > +++ b/sound/hda/hdac_device.c
> > @@ -611,10 +611,9 @@ EXPORT_SYMBOL_GPL(snd_hdac_power_up_pm);
> >   int snd_hdac_keep_power_up(struct hdac_device *codec)
> >   {
> >   	if (!atomic_inc_not_zero(&codec->in_pm)) {
> > -		int ret = pm_runtime_get_if_in_use(&codec->dev);
> > -		if (!ret)
> > +		if (!pm_runtime_active(&codec->dev))
> >   			return -1;
> > -		if (ret < 0)
> > +		if (pm_runtime_get_sync(&codec->dev) < 0)
> >   			return 0;
> >   	}
> >   	return 1;
> 
> 
> This one seems to work, as in I'm able to record before first suspend
> hits. However device stays in D0 when no stream is running...
> # cat /sys/devices/pci0000\:00/0000\:00\:0e.0/power_state
> D0

OK, one step forward.  The previous change was bad in anyway, as we
shouldn't sync there at all.

So, the problem becomes clearer now: it's in the lazy update mechanism
that misses the case that has to be written.

Scratch the previous one again, and could you try the following one
instead?


Takashi

--- a/sound/hda/hdac_regmap.c
+++ b/sound/hda/hdac_regmap.c
@@ -293,8 +293,17 @@ static int hda_reg_write(void *context, unsigned int reg, unsigned int val)
 
 	if (verb != AC_VERB_SET_POWER_STATE) {
 		pm_lock = codec_pm_lock(codec);
-		if (pm_lock < 0)
-			return codec->lazy_cache ? 0 : -EAGAIN;
+		if (pm_lock < 0) {
+			/* skip the actual write if it's in lazy-update mode
+			 * and only if the device is actually suspended;
+			 * the usage count can be zero at transition phase
+			 * (either suspending/resuming or auto-suspend sleep)
+			 */
+			if (codec->lazy_cache &&
+			    pm_runtime_suspended(&codec->dev))
+				return 0;
+			return -EAGAIN;
+		}
 	}
 
 	if (is_stereo_amp_verb(reg)) {