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

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Date:   Wed, 16 Dec 2020 23:50:20 +0800
From:   Kai-Heng Feng <kai.heng.feng@...onical.com>
To:     Takashi Iwai <tiwai@...e.de>
Cc:     tiwai@...e.com, Jaroslav Kysela <perex@...ex.cz>,
        Kai Vehmanen <kai.vehmanen@...ux.intel.com>,
        Pierre-Louis Bossart <pierre-louis.bossart@...ux.intel.com>,
        Alex Deucher <alexander.deucher@....com>,
        Mike Rapoport <rppt@...nel.org>,
        "moderated list:SOUND" <alsa-devel@...a-project.org>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] ALSA: hda: Continue to probe when codec probe fails

On Wed, Dec 16, 2020 at 11:41 PM Takashi Iwai <tiwai@...e.de> wrote:
>
> On Wed, 16 Dec 2020 13:47:24 +0100,
> Kai-Heng Feng wrote:
> >
> > Similar to commit 9479e75fca37 ("ALSA: hda: Keep the controller
> > initialization even if no codecs found"), when codec probe fails, it
> > doesn't enable runtime suspend, and can prevent graphics card from
> > getting powered down:
> > [    4.280991] snd_hda_intel 0000:01:00.1: no codecs initialized
> >
> > $ cat /sys/bus/pci/devices/0000:01:00.1/power/runtime_status
> > active
> >
> > So mark there's no codec and continue probing to let runtime PM to work.
> >
> > BugLink: https://bugs.launchpad.net/bugs/1907212
> > Signed-off-by: Kai-Heng Feng <kai.heng.feng@...onical.com>
>
> Hm, but if the probe fails, doesn't it mean something really wrong?
> IOW, how does this situation happen?

The HDA controller is forcely created by quirk_nvidia_hda(). So
probably there's really not an HDA controller.

>
> The usual no-codec state is for the devices that have a bogus HD-audio
> bus remaining while codecs aren't hooked or disabled by BIOS.  For
> that, it makes to leave the controller driver and let it idle.  But if
> you get really an error, it's something to fix there, not to just
> ignore in general.

The best approach I can think of is to make current two steps probe
into one. So when probe fails, the driver won't bind to the device.
What's the reason behind the two steps approach?

Kai-Heng

>
>
> thanks,
>
> Takashi
>
> > ---
> >  sound/pci/hda/hda_intel.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/sound/pci/hda/hda_intel.c b/sound/pci/hda/hda_intel.c
> > index 6852668f1bcb..872a703dee43 100644
> > --- a/sound/pci/hda/hda_intel.c
> > +++ b/sound/pci/hda/hda_intel.c
> > @@ -2328,7 +2328,7 @@ static int azx_probe_continue(struct azx *chip)
> >       if (bus->codec_mask) {
> >               err = azx_probe_codecs(chip, azx_max_codecs[chip->driver_type]);
> >               if (err < 0)
> > -                     goto out_free;
> > +                     bus->codec_mask = 0;
> >       }
> >
> >  #ifdef CONFIG_SND_HDA_PATCH_LOADER
> > --
> > 2.29.2
> >