[alsa-devel] Problems with the DP MST audio support patchset

[Michael Forney]

On Thu, Mar 30, 2017 at 9:35 AM, Pascal Wichmann
<pascal.wichmann at pa-w.de> wrote:
> -----BEGIN PGP SIGNED MESSAGE-----
> Hash: SHA256
>
> Hi,
>
>> Do you mean the issue is caused by the patches
>> 1480992519-108079-1-git-send-email-libin.yang at intel.com?
> I don't know whether the issues are caused directly by the
> specific patches; without them, digital audio does not work at
> all in my setup. Using analog audio however does not have the problems
> mentioned in my first email.
>
>> I can't see which patches are included you mentioned in the link.
> I am building my kernel from drm-tip. The relevant patches enabling DP M
> ST
> audio seem to be "ALSA: hda - add DP mst verb support" [0] as well as
> "ALSA: hda - add DP MST audio support" [1].

Hi,

I recently updated my kernel to 4.11, and am experiencing similar
problems as Pascal. I have a Skylake processor and DP output hooked up
with a DP to HDMI cable to an Onkyo SR-606 receiver.

I can't get audio to work at all through my receiver anymore. I tried
both DTS and PCM audio files. I bisected it to the above mentioned
commit 9152085defb6426ce8f9989ca27e4450daefbd89 (ALSA: hda - add DP
MST audio support).

>> Do you know if the DP MST audio mode is used in your case?

I don't know what DP MST is or how to tell if I'm using it. However, I
noticed that when it does work, `aplay -L` gives me

hdmi:CARD=PCH,DEV=0
    HDA Intel PCH, HDMI 0
    HDMI Audio Output
hdmi:CARD=PCH,DEV=1
    HDA Intel PCH, HDMI 1
    HDMI Audio Output

and when it doesn't, I get

hdmi:CARD=PCH,DEV=0
    HDA Intel PCH, Generic Digital
    HDMI Audio Output

> I think it is used; at least dp/hdmi audio does not work at all without
> building against drm-tip. (the outputs are all stated as unplugged
> and unavailable in pavucontrol for example)
> Is there any way to know for sure?

I tried building against drm-tip as well as v4.12-rc2, but observed
the same issue. I am not using pulseaudio, but alsa directly.

Any help would be appreciated.

Thanks,
Michael