Re: [PATCH 4/4] ALSA: hda - Wake the codec up on pin/ELD notify events

From: "Ville Syrjälä" <ville.syrjala@linux.intel.com>
To: David Henningsson <david.henningsson@canonical.com>
Cc: Takashi Iwai <tiwai@suse.de>,
	"Vetter, Daniel" <daniel.vetter@intel.com>,
	"alsa-devel@alsa-project.org" <alsa-devel@alsa-project.org>,
	"intel-gfx@lists.freedesktop.org"
	<intel-gfx@lists.freedesktop.org>
Subject: Re: [PATCH 4/4] ALSA: hda - Wake the codec up on pin/ELD notify events
Date: Thu, 26 Nov 2015 17:43:23 +0200	[thread overview]
Message-ID: <20151126154323.GD4437@intel.com> (raw)
In-Reply-To: <56572548.1020603@canonical.com>

On Thu, Nov 26, 2015 at 04:29:12PM +0100, David Henningsson wrote:
> 
> 
> On 2015-11-26 16:23, Takashi Iwai wrote:
> > On Thu, 26 Nov 2015 16:08:06 +0100,
> > David Henningsson wrote:
> >>
> >>
> >>
> >> On 2015-11-26 10:24, Takashi Iwai wrote:
> >>> On Thu, 26 Nov 2015 10:16:17 +0100,
> >>> Zhang, Xiong Y wrote:
> >>>>
> >>>>
> >>>>> On Thu, 26 Nov 2015 08:57:30 +0100,
> >>>>> Zhang, Xiong Y wrote:
> >>>>>>
> >>>>>>>>> BTW, I have a patchset to avoid the audio h/w wakeup by a new
> >>>>>>>>> component ops to get ELD and connection states.  It was posted to
> >>>>>>>>> alsa-devel shortly ago just as a reference, but this should work well
> >>>>>>>>> in such a case, too.  The test patches are found in test/hdmi-jack
> >>>>>>>>> branch of my sound git tree.
> >>>>>>>
> >>>>>>> Did you try this branch (merge onto intel-test-nightly)?
> >>>>>>>
> >>>>>> [Zhang, Xiong Y] Yes, this branch could fix my issue.
> >>>>>
> >>>>> OK, good to hear.  But this isn't for 4.4 or backport, as it's more
> >>>>> radical changes.
> >>>>>
> >>>>> Could you check the patch below instead?  This suppresses the notifier
> >>>>> handling during suspend.  It's bad, but the hotplug should be still
> >>>>> handled via normal unsol event, so it should keep working, good enough
> >>>>> as a stop gap.
> >>>>>
> >>>>>
> >>>>> Takashi
> >>>>>
> >>>>> ---
> >>>>> diff --git a/sound/pci/hda/patch_hdmi.c b/sound/pci/hda/patch_hdmi.c
> >>>>> index bdb6f226d006..f7c70e2ae65c 100644
> >>>>> --- a/sound/pci/hda/patch_hdmi.c
> >>>>> +++ b/sound/pci/hda/patch_hdmi.c
> >>>>> @@ -33,6 +33,7 @@
> >>>>>    #include <linux/delay.h>
> >>>>>    #include <linux/slab.h>
> >>>>>    #include <linux/module.h>
> >>>>> +#include <linux/pm_runtime.h>
> >>>>>    #include <sound/core.h>
> >>>>>    #include <sound/jack.h>
> >>>>>    #include <sound/asoundef.h>
> >>>>> @@ -2352,7 +2353,9 @@ static void intel_pin_eld_notify(void *audio_ptr, int
> >>>>> port)
> >>>>>    	struct hda_codec *codec = audio_ptr;
> >>>>>    	int pin_nid = port + 0x04;
> >>>>>
> >>>>> -	check_presence_and_report(codec, pin_nid);
> >>>>> +	if (!atomic_read(&codec->core.in_pm) &&
> >>>>> +	    !pm_runtime_suspended(hda_codec_dev(codec)))
> >>>>> +		check_presence_and_report(codec, pin_nid);
> >>>>>    }
> >>>>>
> >>>>>    static int patch_generic_hdmi(struct hda_codec *codec)
> >>>> [Zhang, Xiong Y]  this patch couldn't remove the error message. So audio controller isn't in Runtime D3 after azx_suspend().
> >>>
> >>> OK, then the problem isn't about the HD-audio driver but rather i915
> >>> driver.  As already mentioned, i915 driver shouldn't issue eld_notify
> >>> callback in the suspend code path.
> >>
> >> We don't have a complete drm log so I'm only speculating here; but the
> >> HDA log seems to indicate the power well is off when we try to talk to
> >> the HDA controller. That means either the i915 shut it down while we
> >> were holding a lock on it, or HDA tried to lock it and that didn't make
> >> it through; in which case the HDA side should handle an error from
> >> get_power more gracefully...?
> >
> > My understanding is that it's triggered *during* i915 suspend.  Then
> > the path calls the HDA callback, and HDA controller tries to get power
> > and proceeds as it has no idea that it's being shut off.
> 
> Well; that can also be stopped by letting the get_power call return a 
> failure code in case i915 is trying to suspend itself. That seems more 
> robust to me, as it could potentially avoid other S3 races too...?
> 
> >
> > Unfortunately, neither get_power callback or the corresponding HDA
> > code has a capability to check that state.  So, changing / fixing this
> > there would be nice but very hard.
> 
> Surely the i915 driver has some "am_i_suspending" variable it can check 
> in the get_power callback?

I don't understand why you need to do anything special. When the eld
notify happens during suspend, the hardware is still fully powered up,
so it should just work(tm) as long as the eld_notify is a synchronous
call and it drops the power reference at the end.

I guess for any get_power after i915 has suspended we'd need to just
reject the get_power call. Or does something force hda to suspend before
and resume after i915 always?

-- 
Ville Syrjälä
Intel OTC
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