[alsa-devel] Regression due to 6169b673618b "ALSA: hda - Always turn on pins for HDMI/DP"

[Takashi Iwai]

At Wed, 29 Jan 2014 16:34:11 -0700,
Stephen Warren wrote:
> 
> Takashi,
> 
> It looks like commit 6169b673618b "ALSA: hda - Always turn on pins for
> HDMI/DP" has caused a regression on NVIDIA graphics cards. It's been
> reported to us by at least two separate users.
> 
> On NVIDIA GPUs, it appears that if multiple pin complex widgets have
> their input mux set to the same audio output widget and PIN_OUT, then
> only one of the pin complex widgets will actually receive the audio.
> That's the reason we need to dynamically toggle PIN_OUT on and off, so
> that only actually active pin complex widgets are enabled. Without this,
> audio will be routed to the same pin complex all the time, rather than
> the user-selected device. I'm not sure if this is the way HDA CODECs are
> meant to work, but it certainly is how they do work:-)

AFAIK, there is no concrete definitions.

> So, I'd like to basically revert 6169b673618b "ALSA: hda - Always turn
> on pins for HDMI/DP", and return the code to the state it was after
> commit 384a48d71520 "ALSA: hda: HDMI: Support codecs with fewer cvts
> than pins". However, I obviously don't want to re-introduce the
> regression that your commit solved. I think we should solve this by
> including the code for both behaviours in the kernel, and having either
> a flag in struct hdmi_spec, or some extra ops in struct hdmi_ops, select
> between the two paths. Does that seem reasonable?

Yes, that's a good option.  I don't mind either way.

> If so, the only remaining question is: which behaviour should be default
> a/k/a should I blacklist the problematic GM965 (mentioned in
> https://bugzilla.kernel.org/show_bug.cgi?id=51421) against having the
> dynamic PIN_OUT behaviour, or whitelist NVIDIA GPUs as requiring the
> dynamic PIN_OUT behaviour? I know that my patch worked fine on my wife's
> Intel chipset, but I have no idea if the dynamic PIN_OUT behaviour was
> actually needed there, or simply tolerated, and I have no way to test
> much aside from NVIDIA GPUs. That all said, the dynamic PIN_OUT
> behaviour seems to make most sense to me, or some systems may end up
> with audio being sent to multiple outputs when only one was expected.

My vote is to apply the dynamic PIN_OUT only for Nvidia.
AMD devices have been tested with the recent kernels, so they should
be no problem with static PIN_OUT setting.  Some Intel chip seem to
mandate it.  And the rest devices have no multiple pins, in anyway :)

Could you care the fix patch?


thanks,

Takashi