Nouveau - Apr 2021 - [PATCH v2] ALSA: hda: Continue to probe when codec probe fails

On Sat, Apr 10, 2021 at 04:51:27PM +0100, Roy Spliet
wrote:
> Can I ask someone with more
> technical knowledge of snd_hda_intel and vgaswitcheroo to brainstorm about
> the possible challenges of nouveau taking matters into its own hand rather
> than keeping this PCI quirk around?
It sounds to me like the HDA is not powered if no cable is plugged in.
What is reponsible then for powering it up or down, firmware code on
the GPU or in the host's BIOS?

Ideally, we should try to find out how to control HDA power from the
operating system rather than trying to cooperate with whatever firmware
is doing.  If we have that capability, the OS should power the HDA up
and down as it sees fit.

Thanks,

Lukas

Op 10-04-2021 om 20:23 schreef Lukas Wunner:
> On Sat, Apr 10, 2021 at 04:51:27PM +0100, Roy Spliet wrote:
>> Can I ask someone with more
>> technical knowledge of snd_hda_intel and vgaswitcheroo to brainstorm
about
>> the possible challenges of nouveau taking matters into its own hand
rather
>> than keeping this PCI quirk around?
> 
> It sounds to me like the HDA is not powered if no cable is plugged in.
> What is reponsible then for powering it up or down, firmware code on
> the GPU or in the host's BIOS?
Sometimes the BIOS, but definitely unconditionally the PCI quirk code: 
https://github.com/torvalds/linux/blob/master/drivers/pci/quirks.c#L5289

(CC Aaron Plattner)
> 
> Ideally, we should try to find out how to control HDA power from the
> operating system rather than trying to cooperate with whatever firmware
> is doing.  If we have that capability, the OS should power the HDA up
> and down as it sees fit.
> 
> Thanks,
> 
> Lukas
>