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

[Kai-Heng Feng]

On Wed, Dec 16, 2020 at 11:58 PM Takashi Iwai <tiwai@xxxxxxx> wrote:
>
> On Wed, 16 Dec 2020 16:50:20 +0100,
> Kai-Heng Feng wrote:
> >
> > On Wed, Dec 16, 2020 at 11:41 PM Takashi Iwai <tiwai@xxxxxxx> 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@xxxxxxxxxxxxx>
> > >
> > > 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.
>
> I still don't understand how non-zero codec_mask is passed.
> The non-zero codec_mask means that BIOS or whatever believes that
> HD-audio codecs are present and let HD-audio controller reporting the
> presence.  What error did you get at probing?

[    4.280991] snd_hda_intel 0000:01:00.1: no codecs initialized
Full dmesg here:
https://launchpadlibrarian.net/510351476/dmesg.log

>
>
> > > 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?
>
> It's a sort of must, as the module loading is involved with binding
> with the codecs, as well as (optionally) request_firmware()
> invocation.

Ok. I also tried to use device_release_driver(), but azx_remove()
calls "cancel_work_sync(&hda->probe_work)" so there will be a
deadlock.

Kai-Heng

>
>
> Takashi



-- 
Kai-Heng