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Subject: Re: [Nouveau] [PATCH v2] ALSA: hda: Continue to probe when codec
 probe fails
To:     Lukas Wunner <lukas@wunner.de>
Cc:     Karol Herbst <kherbst@redhat.com>,
        Kai-Heng Feng <kai.heng.feng@canonical.com>,
        "moderated list:SOUND" <alsa-devel@alsa-project.org>,
        Kai Vehmanen <kai.vehmanen@linux.intel.com>,
        Takashi Iwai <tiwai@suse.de>,
        nouveau <nouveau@lists.freedesktop.org>,
        Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>,
        tiwai@suse.com, Alex Deucher <alexander.deucher@amd.com>,
        Alan Stern <stern@rowland.harvard.edu>,
        Mike Rapoport <rppt@kernel.org>,
        Linux PCI <linux-pci@vger.kernel.org>,
        Bjorn Helgaas <bhelgaas@google.com>,
        Jaroslav Kysela <perex@perex.cz>,
        open list <linux-kernel@vger.kernel.org>,
        Aaron Plattner <aplattner@nvidia.com>
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From:   Roy Spliet <nouveau@spliet.org>
Message-ID: <bddba2ca-15d5-7fd3-5b64-f4ba7e179ec0@spliet.org>
Date:   Sat, 10 Apr 2021 21:48:15 +0100
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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
>