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Date:   Fri, 18 Dec 2020 09:06:29 +0100
From:   Takashi Iwai <tiwai@...e.de>
To:     Kai-Heng Feng <kai.heng.feng@...onical.com>
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>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Alan Stern <stern@...land.harvard.edu>,
        Linux PCI <linux-pci@...r.kernel.org>
Subject: Re: [PATCH v2] ALSA: hda: Continue to probe when codec probe fails

On Fri, 18 Dec 2020 06:09:38 +0100,
Kai-Heng Feng wrote:
> 
> [+Cc Bjorn, Alan and linux-pci]
> 
> On Thu, Dec 17, 2020 at 12:57 AM Takashi Iwai <tiwai@...e.de> wrote:
> >
> > On Wed, 16 Dec 2020 17:22:17 +0100,
> > Takashi Iwai wrote:
> > >
> > > On Wed, 16 Dec 2020 17:07:45 +0100,
> > > Kai-Heng Feng wrote:
> > > >
> > > > On Wed, Dec 16, 2020 at 11:58 PM Takashi Iwai <tiwai@...e.de> 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@...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.
> > > > >
> > > > > 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 actual problems are shown before that line.
> > >
> > > [    4.178848] pci 0000:01:00.1: can't change power state from D3cold to D0 (config space inaccessible)
> > > [    4.179502] snd_hda_intel 0000:01:00.1: can't change power state from D3cold to D0 (config space inaccessible)
> > > [    4.179511] snd_hda_intel 0000:01:00.1: can't change power state from D3hot to D0 (config space inaccessible)
> > > ....
> > > [    4.280571] hdaudio hdaudioC1D0: no AFG or MFG node found
> > > [    4.280633] hdaudio hdaudioC1D1: no AFG or MFG node found
> > > [    4.280685] hdaudio hdaudioC1D2: no AFG or MFG node found
> > > [    4.280736] hdaudio hdaudioC1D3: no AFG or MFG node found
> > > [    4.280788] hdaudio hdaudioC1D4: no AFG or MFG node found
> > > [    4.280839] hdaudio hdaudioC1D5: no AFG or MFG node found
> > > [    4.280892] hdaudio hdaudioC1D6: no AFG or MFG node found
> > > [    4.280943] hdaudio hdaudioC1D7: no AFG or MFG node found
> > >
> > > Could you check the codec_mask value read in
> > > sound/hda/hdac_controller.c?  I guess it reads 0xff.
> > >
> > > If that's the case, it can be corrected by the patch below.
> > > But, we should check the cause of the first error (inaccessible config
> > > space) in anyway; this must be the primary reason of the whole chain
> > > of errors.
> >
> > Now I took a deeper look at the code.  So we hit errors after errors:
> > - The first problem is that quirk_nvidia_hda() enabled HD-audio even
> >   if it's non-functional by some reason.  We may need additional
> >   checks there.
> 
> Quite possibly the system doesn't power up HDA controller when there's
> no external monitor.
> So when it's connected to external monitor, it's still needed for HDMI audio.
> Let me ask the user to confirm this.

Yeah, it's the basic question whether the HD-audio is supposed to work
on this machine at all.  If yes, the current approach we take makes
less sense - instead we should rather make the HD-audio controller
working.

> > - The second problem is that pci_enable_device() ignores the error
> >   returned from pci_set_power_state() if it's -EIO.  And the
> >   inaccessible access error returns -EIO, although it's rather a fatal
> >   problem.  So the driver believes as the PCI device gets enabled
> >   properly.
> 
> This was introduced in 2005, by Alan's 11f3859b1e85 ("[PATCH] PCI: Fix
> regression in pci_enable_device_bars") to fix UHCI controller.
> 
> >
> > - The third problem is that HD-audio driver blindly believes the
> >   codec_mask read from the register even if it's a read failure as I
> >   already showed.
> 
> This approach has least regression risk.

Yes, but it assumes that HD-audio is really non-existent.


thanks,

Takashi

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