Re: [PATCH] ALSA: hda: intel: Fix Optimus when GPU has no sound

[Takashi Iwai <tiwai@xxxxxxx>]

On Fri, 06 Sep 2024 20:05:06 +0200,
Maxim Mikityanskiy wrote:
> 
> On Thu, 05 Sep 2024 at 16:24:26 +0200, Takashi Iwai wrote:
> > On Wed, 04 Sep 2024 22:39:55 +0200,
> > Maxim Mikityanskiy wrote:
> > > 
> > > Lenovo IdeaPad Z570 with NVIDIA GeForce Ge 520M doesn't have sound on
> 
> Spotted a typo: s/520M/540M/
> 
> > > the discrete GPU. snd_hda_intel probes the device and schedules
> > > azx_probe_continue(), which fails at azx_first_init(). The driver ends
> > > up probed, but calls azx_free() and stops the chip. However, from the
> > > runtime PM point of view, the device remains active, because the PCI
> > > subsystem makes it active on probe, and it's still bound. It prevents
> > > vga_switcheroo from turning off the DGPU (pci_create_device_link() syncs
> > > power management for the video and audio devices).
> > > 
> > > Fix it by forcing the device to the suspended state in azx_free().
> > > 
> > > Fixes: 07f4f97d7b4b ("vga_switcheroo: Use device link for HDA controller")
> > > Signed-off-by: Maxim Mikityanskiy <maxtram95@xxxxxxxxx>
> > 
> > What if this device probe is skipped (e.g. adding your device entry to
> > driver_denylist[] in hda_intel.c)?  Is the device also in the
> > runtime-suspended state?
> 
> I added the following:
> 
> { PCI_DEVICE_SUB(0x10de, 0x0bea, 0x0000, 0x0000) },
> 
> The probe was apparently skipped (the device is not attached to a
> driver), runtime_status=suspended, runtime_usage=0, the GPU goes to
> DynOff.

OK, that's good.

> However, I'm not sure whether it's a good idea to blacklist 540M
> entirely, as there might be other laptops with this GPU that have sound,
> and AFAIK there are variants of Lenovo Z570 with other NVIDIA GPUs.

You should specify the PCI SSID of your device instead of 0:0 in the
above, so that it's picked up only for yours.


Takashi

> Another way to make vga_switcheroo work is to disable quirk_nvidia_hda,
> although I don't know whether it can be done without recompiling the
> kernel. In this case, 0000:01:00.1 doesn't even appear on the bus.
> 
> (Note that I need to set nouveau.modeset=2 either way, otherwise it
> stays in DynPwr if the screen is on.)
> 
> > 
> > 
> > thanks,
> > 
> > Takashi
> > 
> > > ---
> > >  sound/pci/hda/hda_intel.c | 14 +++++++++++++-
> > >  1 file changed, 13 insertions(+), 1 deletion(-)
> > > 
> > > diff --git a/sound/pci/hda/hda_intel.c b/sound/pci/hda/hda_intel.c
> > > index b79020adce63..65fcb92e11c7 100644
> > > --- a/sound/pci/hda/hda_intel.c
> > > +++ b/sound/pci/hda/hda_intel.c
> > > @@ -1361,8 +1361,20 @@ static void azx_free(struct azx *chip)
> > >  	if (use_vga_switcheroo(hda)) {
> > >  		if (chip->disabled && hda->probe_continued)
> > >  			snd_hda_unlock_devices(&chip->bus);
> > > -		if (hda->vga_switcheroo_registered)
> > > +		if (hda->vga_switcheroo_registered) {
> > >  			vga_switcheroo_unregister_client(chip->pci);
> > > +
> > > +			/* Some GPUs don't have sound, and azx_first_init fails,
> > > +			 * leaving the device probed but non-functional. As long
> > > +			 * as it's probed, the PCI subsystem keeps its runtime
> > > +			 * PM status as active. Force it to suspended (as we
> > > +			 * actually stop the chip) to allow GPU to suspend via
> > > +			 * vga_switcheroo.
> > > +			 */
> > > +			pm_runtime_disable(&pci->dev);
> > > +			pm_runtime_set_suspended(&pci->dev);
> > > +			pm_runtime_enable(&pci->dev);
> > > +		}
> > >  	}
> > >  
> > >  	if (bus->chip_init) {
> > > -- 
> > > 2.46.0
> > >