linux-kernel - Re: [Nouveau] [PATCH v2] ALSA: hda: Continue to probe when codec probe fails

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Date:   Sat, 10 Apr 2021 21:23:14 +0200
From:   Lukas Wunner <lukas@...ner.de>
To:     Roy Spliet <nouveau@...iet.org>
Cc:     Karol Herbst <kherbst@...hat.com>,
        Kai-Heng Feng <kai.heng.feng@...onical.com>,
        "moderated list:SOUND" <alsa-devel@...a-project.org>,
        Kai Vehmanen <kai.vehmanen@...ux.intel.com>,
        Takashi Iwai <tiwai@...e.de>,
        nouveau <nouveau@...ts.freedesktop.org>,
        Pierre-Louis Bossart <pierre-louis.bossart@...ux.intel.com>,
        tiwai@...e.com, Alex Deucher <alexander.deucher@....com>,
        Alan Stern <stern@...land.harvard.edu>,
        Mike Rapoport <rppt@...nel.org>,
        Linux PCI <linux-pci@...r.kernel.org>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Jaroslav Kysela <perex@...ex.cz>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [Nouveau] [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