[alsa-devel] [PATCH 2/2] [RFC] ALSA: hda: hdmi - preserve non-MST PCM routing for Intel platforms

[Kai Vehmanen]

Hey,

On Mon, 2 Dec 2019, Nikhil Mahale wrote:

> On 11/29/19 8:07 PM, Kai Vehmanen wrote:
> > In the drm_audio_component.h interface, the third parameter
> > to pin_eld_notify() is pipe number. On Intel platforms, this value
> > is -1 for MST. On other platforms, a non-zero pipe id is used to
> 
> Do you mean "on Intel platforms, this value is -1 for non-MST"?
[...]
> I am looking into functions
> intel_audio_codec_enable/intel_audio_codec_disable, they sets
> pipe = -1 for non-MST cases, right?

yup, -1 for non-MST, that was just plain wrong in my Friday mail. The 
problem seems to be pipe id is positive in some non-MST cases (like 
https://github.com/thesofproject/linux/issues/1536 ), which is very 
suprising looking at e.g. intel_audio_codec_enable(), but that seems to be 
happening nevertheless.

This would seem like a lurking bug on the i915 graphics driver side. Your 
patch changed the behaviour in these cases on ALSA side (PCM was selected 
based on per_pin->pin_nid_idx, ignoring dev_id), but one can argue whether 
this is worth preserving (or just drop/revert the RFC patch). I'll try to 
get a bit more info on the rootcause and how common case this is.

Br,
Kai