[alsa-devel] [PATCH 3/4] ALSA: hda - display audio call ncts callback

[Yang, Libin]

Hi Takashi,

> -----Original Message-----
> From: Takashi Iwai [mailto:tiwai at suse.de]
> Sent: Thursday, August 06, 2015 6:03 PM
> To: Yang, Libin
> Cc: alsa-devel at alsa-project.org; intel-gfx at lists.freedesktop.org; Lin,
> Mengdong
> Subject: Re: [PATCH 3/4] ALSA: hda - display audio call ncts callback
> 
> On Thu, 06 Aug 2015 08:52:56 +0200,
> libin.yang at intel.com wrote:
> >
> > From: Libin Yang <libin.yang at intel.com>
> >
> > On some Intel platforms, display audio need set N/CTS
> > manually at some TMDS frequencies.
> >
> > Signed-off-by: Libin Yang <libin.yang at intel.com>
> > ---
> >  sound/pci/hda/patch_hdmi.c | 7 +++++++
> >  1 file changed, 7 insertions(+)
> >
> > diff --git a/sound/pci/hda/patch_hdmi.c
> b/sound/pci/hda/patch_hdmi.c
> > index a97db5f..4bd11ff 100644
> > --- a/sound/pci/hda/patch_hdmi.c
> > +++ b/sound/pci/hda/patch_hdmi.c
> > @@ -1786,6 +1786,8 @@ static int
> generic_hdmi_playback_pcm_prepare(struct hda_pcm_stream *hinfo,
> >  	int pin_idx = hinfo_to_pin_index(codec, hinfo);
> >  	struct hdmi_spec_per_pin *per_pin = get_pin(spec, pin_idx);
> >  	hda_nid_t pin_nid = per_pin->pin_nid;
> > +	struct snd_pcm_runtime *runtime = substream->runtime;
> > +	struct i915_audio_component *acomp = codec->bus-
> >core.audio_component;
> >  	bool non_pcm;
> >  	int pinctl;
> >
> > @@ -1802,6 +1804,11 @@ static int
> generic_hdmi_playback_pcm_prepare(struct hda_pcm_stream *hinfo,
> >  		intel_not_share_assigned_cvt(codec, pin_nid, per_pin-
> >mux_idx);
> >  	}
> >
> > +	if (is_haswell_plus(codec)) {
> > +		if (acomp && acomp->ops && acomp->ops->set_ncts)
> > +			acomp->ops->set_ncts(acomp->dev, per_pin-
> >pin_nid - 4,
> 
> Please describe more how "pin_nid - 4" is supposed to work.  Also...

OK, I see.

> 
> > +				0, runtime->rate);
> 
> ... this implies that no MST support included?

We will support MST later. Currently I just add the
interface to support MST, but not implementing it.

After we enabled MST, I will submit another patch
to support MST. Currently, it seems the display audio
driver need do some change to support MST.

> 
> Overall, it'd be appreciated if you put more information text in
> changelog or comment.  it series looks like a black magic to me unless
> clearly explained.

OK, I will add the comments about the details.

> 
> 
> thanks,
> 
> Takashi