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

[Raymond Yau]

>
> > -----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.

Refer to DCN HDA040-A

Multi-stream over Single Display Port

Can the driver use subdevices for those display port support multi
streaming ?

The specification allow up to 64 device entries

This mean the number of subdevices is equal to the device list length

More than one audio output /converters can be connected to the multi stream
displayport pin widget but different device entry while only one audio
output can be dynamically allocated  to other HDMI pin widget

7.3.3.42 Device Select

For Digital Display Pin Widget that is multi stream capable, the Device
Select control determines which Device Entry is currently selected and
accessible by the Pin Widget verbs which are controlling the sink device
operations.  This control verb is only required if it is a Digital Display
Pin Widget and multi stream capable.

The index is in relation to the Device List associated with the widget.
The index is a zero-based offset into the Device List.  Once the Device
Entry is selected by the Set index, all subsequent Pin Widget verbs
controlling the sink device operations will be directed to the selected
Device Entry, until the Device Select verb get updated with a new value.

Device Entry: Indicate the index of Device Entry (0 63) which the UR bit of
is generated for a multi stream capable Digital Display Pin Widget.  Not
valid for non Digital Display Pin Widget or Digital Display Pin Widget that
is not multi stream capable

Device List Length is a 0 based integer value indicating the number of sink
device that a multi stream capable Digital Display Pin Widget can support.
If Device List Length is value is 0, there is only one sink device
connection possible indicating the Pin Widget is not multi stream capable,
and there is no Device Select control (see Section 7.3.3.42).  If the
Device List Length value is 1 – 63, it indicates the Pin Widget is multi
stream capable, and 2 – 64 Device Entries are supported in the Pin Widget.
>