[Intel-gfx] [PATCH 3/4] ALSA: hda - display audio call ncts callback

[Takashi Iwai]

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...

> +				0, runtime->rate);

... this implies that no MST support included?

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.


thanks,

Takashi