Re: [PATCH] ALSA: hda - verify pin:cvt connection on preparing a stream for Intel HDMI codec

From: "Lin, Mengdong" <mengdong.lin@intel.com>
To: Takashi Iwai <tiwai@suse.de>
Cc: "alsa-devel@alsa-project.org" <alsa-devel@alsa-project.org>
Subject: Re: [PATCH] ALSA: hda - verify pin:cvt connection on preparing a stream for Intel HDMI codec
Date: Wed, 19 Mar 2014 04:00:41 +0000	[thread overview]
Message-ID: <F46914AEC2663F4A9BB62374E5EEF8F82B31AE02@SHSMSX151.ccr.corp.intel.com> (raw)
In-Reply-To: <s5ha9cnpmw8.wl%tiwai@suse.de>

Hi Takashi,

> -----Original Message-----
> From: Takashi Iwai [mailto:tiwai@suse.de]
> Sent: Tuesday, March 18, 2014 11:06 PM

> > > > The pin:converter connection may get reset after S3 on Intel
> > > > Broadwell HDMI codec. And this can cause multiple pins share a
> > > > same convertor and mute control will affect each other. We
> > > > observed a resumed audio playback become silent after S3.
> > > >
> > > > This patch verifies pin:cvt connection on preparing a stream, to
> > > > assure the pin selects the right convetor and an assigned
> > > > convertor is not shared by other unused pins. Apply this fix-up on
> > > > Haswell,
> > > Broadwell and Baytrail.
> > > >
> > > > Signed-off-by: Mengdong Lin <mengdong.lin@intel.com>
> > >
> > > Hm, it's still not clear to me why this happens.  The connections
> > > are recorded via snd_hda_codec_write_cache(), and these values
> > > should be restored in the resume.  Where the things went wrong?
> >
> > I don't think it's the problem of snd_hda_codec_write_cache().
> >
> > When the pcm stream is opened, the convertor to pin connection is
> > configured by the driver, not interrupted by S3, and then playback start.
> 
> Yes.  And at this moment, the connection was already saved in the cache
> via snd_hda_codec_write_cache().
> 
> > But after S3, HW forgets this configuration and pin can select the
> > default convertor.
> 
> ... but the driver restores the old connection read from the cache.
> So, after S3 resume, this connection should have been already restored.
> Also the connections of other converters should be also covered, as they
> are set with snd_hda_codec_write_cache() in
> intel_not_share_assigned_cvt().
> 
> > Thus a used pin and an unused pin can share a same convertor and a
> muted pin can make the other used pin no sound output.
> > As a result, a resumed playback after S3 can have no sound output.
> 
> I'm afraid that there is a big missing piece here.
> Check whether the cached values are really restored properly in the
> resume.  snd_hda_codec_resume_cache() does it.

Thanks for your tips!
snd_hda_codec_resume_cache() works well as expected, it does apply the convertor selections for all pins with the right cached value.

So the big missing piece here is the audio driver restores things earlier than gfx side is ready, and such connect selection is overlooked by HW.
After Gfx is ready, the pins make the default selection again.

I think the better solution is to let gfx driver tell audio when it's ready by the new communication channel as we discussed before. 
And probably we could delay generic_hdmi_resume until gfx notify it's ready.

Not only the pin:cvt connection, but pin's power state/muting status also depend on gfx status as we observed before.
Unsolicited event is not reliable and will be lost when the audio controller in D3 and ELD in HW buffer can be broken if the display power well has on/off. 
A SW channel will be more reliable than using unsol event and checking ELD by pin_sense.

Sorry that the implementation on audio/gfx channel has been pending so long due to other internal tasks. 
But now we'd better do this asap since several features is blocked by this.

Thanks
Mengdong

> 
> > The commit f82d7d16aee5eb4c2315ba11a90f2f3c662d45b8 (ALSA : hda -
> not use assigned converters for all unused pins) is to avoid convertor
> sharing when a pcm stream is opened.
> > Now this patch will verify pin:converter connection and avoid convertor
> sharing when preparing the stream, for resuming a stream after S3.
> >
> > Although this issue after S3 is only observed on Broadwell, we want to
> apply it to Haswell and Baytrail (Valleyview) for safety consideration.
> >
> > Thanks
> > Mengdong
> >
> >
> > > >
> > > > diff --git a/sound/pci/hda/patch_hdmi.c
> > > > b/sound/pci/hda/patch_hdmi.c index 3ab7063..6000ce9 100644
> > > > --- a/sound/pci/hda/patch_hdmi.c
> > > > +++ b/sound/pci/hda/patch_hdmi.c
> > > > @@ -68,6 +68,7 @@ struct hdmi_spec_per_pin {
> > > >  	hda_nid_t pin_nid;
> > > >  	int num_mux_nids;
> > > >  	hda_nid_t mux_nids[HDA_MAX_CONNECTIONS];
> > > > +	int mux_idx;
> > > >  	hda_nid_t cvt_nid;
> > > >
> > > >  	struct hda_codec *codec;
> > > > @@ -1342,6 +1343,8 @@ static int hdmi_choose_cvt(struct
> hda_codec
> > > *codec,
> > > >  	if (cvt_idx == spec->num_cvts)
> > > >  		return -ENODEV;
> > > >
> > > > +	per_pin->mux_idx = mux_idx;
> > > > +
> > > >  	if (cvt_id)
> > > >  		*cvt_id = cvt_idx;
> > > >  	if (mux_id)
> > > > @@ -1350,6 +1353,22 @@ static int hdmi_choose_cvt(struct
> hda_codec
> > > *codec,
> > > >  	return 0;
> > > >  }
> > > >
> > > > +/* Assure the pin select the right convetor */ static void
> > > > +intel_verify_pin_cvt_connect(struct hda_codec *codec,
> > > > +			struct hdmi_spec_per_pin *per_pin) {
> > > > +	hda_nid_t pin_nid = per_pin->pin_nid;
> > > > +	int mux_idx, curr;
> > > > +
> > > > +	mux_idx = per_pin->mux_idx;
> > > > +	curr = snd_hda_codec_read(codec, pin_nid, 0,
> > > > +					  AC_VERB_GET_CONNECT_SEL, 0);
> > > > +	if (curr != mux_idx)
> > > > +		snd_hda_codec_write_cache(codec, pin_nid, 0,
> > > > +					    AC_VERB_SET_CONNECT_SEL,
> > > > +					    mux_idx);
> > > > +}
> > > > +
> > > >  /* Intel HDMI workaround to fix audio routing issue:
> > > >   * For some Intel display codecs, pins share the same connection
> list.
> > > >   * So a conveter can be selected by multiple pins and playback on
> > > > any of these @@ -1751,6 +1770,12 @@ static int
> > > generic_hdmi_playback_pcm_prepare(struct hda_pcm_stream *hinfo,
> > > >  	bool non_pcm;
> > > >  	int pinctl;
> > > >
> > > > +	if (is_haswell_plus(codec) || is_valleyview(codec)) {
> > > > +		/* the pin:cvt connection may get reset after S3 */
> > > > +		intel_verify_pin_cvt_connect(codec, per_pin);
> > > > +		intel_not_share_assigned_cvt(codec, pin_nid,
> > > per_pin->mux_idx);
> > > > +	}
> > > > +
> > > >  	non_pcm = check_non_pcm_per_cvt(codec, cvt_nid);
> > > >  	mutex_lock(&per_pin->lock);
> > > >  	per_pin->channels = substream->runtime->channels;
> > > > --
> > > > 1.8.1.2
> > > >
> >