Re: [alsa-devel] [PATCH v6 2/2] ALSA: hda: Allow HDA to be runtime suspended when dGPU is not bound to a driver

[Jaroslav Kysela]

Dne 10. 01. 20 v 10:56 Takashi Iwai napsal(a):
> On Fri, 10 Jan 2020 10:43:26 +0100,
> Jaroslav Kysela wrote:
> > Dne 18. 10. 19 v 9:38 Kai-Heng Feng napsal(a):
> > > Nvidia proprietary driver doesn't support runtime power management, so
> > > when a user only wants to use the integrated GPU, it's a common practice
> > > to let dGPU not to bind any driver, and let its upstream port to be
> > > runtime suspended. At the end of runtime suspension the port uses
> > > platform power management to disable power through _OFF method of power
> > > resource, which is listed by _PR3.
> > >
> > > After commit b516ea586d71 ("PCI: Enable NVIDIA HDA controllers"), when
> > > the dGPU comes with an HDA function, the HDA won't be suspended if the
> > > dGPU is unbound, so the power resource can't be turned off by its
> > > upstream port driver.
> > >
> > > Commit 37a3a98ef601 ("ALSA: hda - Enable runtime PM only for
> > > discrete GPU") only allows HDA to be runtime suspended once GPU is
> > > bound, to keep APU's HDA working.
> > >
> > > However, HDA on dGPU isn't that useful if dGPU is not bound to any
> > > driver.  So let's relax the runtime suspend requirement for dGPU's HDA
> > > function, to disable the power source to save lots of power.
> >
> > This patch breaks the HDMI audio detection at least on some platforms
> > (Lenovo P50 for example) with nouveau and the proprietary nvidia
> > driver. Those laptops have the external HDMI/DP ports connected to
> > dGPU instead the iGPU. The ACPI PR3 is set.
> >
> > The runtime PM off fixes this problem:
> >
> > echo on > /sys/bus/pci/devices/0000\:01\:00.1/power/control
>
> But this will keep the power of the graphics chip on, and that's what
> the patch was supposed to "fix".
>
> > But I don't think that it's the best solution. My proposal is to
> > create a pr3 check blacklist to keep power for the HDMI audio for
> > those machines. Also we may add a new module parameter for
> > snd-hda-intel to control this. Other ideas?
>
> For nouveau, the best fix is to merge the audio component patch.
> This will make things working without fiddling with the power
> up/down.  The patch has been pending over months under review in DRM
> side, unfortunately...  Please pinging them for driving ahead.

Adding Cc: to dri-devel. You probably mean this thread:

https://lists.freedesktop.org/archives/dri-devel/2019-July/thread.html#227423

> For Nvidia, though, it's no path a binary-only stuff can go with, due
> to the GPL symbol of the component framework.  Those guys know of it
> well, and they seem adding the temporary power up/down procedure by
> poking the proc file from the user-space side at the HDMI connection.

Wow.

> About a module option: I don't think it's much better than the sysfs
> toggle.  You can set up a simple udev rule if needed, too.

Ok, it's a bit nightmare to maintain those extra settings in the distribution.

					Jaroslav

> thanks,
>
> Takashi
>
> > 					Jaroslav
> >
> >
> > > BugLink: https://bugs.launchpad.net/bugs/1840835
> > > Fixes: b516ea586d71 ("PCI: Enable NVIDIA HDA controllers")
> > > Signed-off-by: Kai-Heng Feng <kai.heng.feng@xxxxxxxxxxxxx>
> > > ---
> > > v5, v6:
> > > - No change.
> > > v4:
> > > - Find upstream port, it's callee's responsibility now.
> > > v3:
> > > - Make changelog more clear.
> > > v2:
> > > - Change wording.
> > > - Rebase to Tiwai's branch.
> > >    sound/pci/hda/hda_intel.c | 8 +++++++-
> > >    1 file changed, 7 insertions(+), 1 deletion(-)
> > >
> > > diff --git a/sound/pci/hda/hda_intel.c b/sound/pci/hda/hda_intel.c
> > > index 240f4ca76391..e63b871343e5 100644
> > > --- a/sound/pci/hda/hda_intel.c
> > > +++ b/sound/pci/hda/hda_intel.c
> > > @@ -1280,11 +1280,17 @@ static void init_vga_switcheroo(struct azx *chip)
> > >    {
> > >    	struct hda_intel *hda = container_of(chip, struct hda_intel, chip);
> > >    	struct pci_dev *p = get_bound_vga(chip->pci);
> > > +	struct pci_dev *parent;
> > >    	if (p) {
> > >    		dev_info(chip->card->dev,
> > >    			 "Handle vga_switcheroo audio client\n");
> > >    		hda->use_vga_switcheroo = 1;
> > > -		chip->bus.keep_power = 1; /* cleared in either gpu_bound op or codec probe */
> > > +
> > > +		/* cleared in either gpu_bound op or codec probe, or when its
> > > +		 * upstream port has _PR3 (i.e. dGPU).
> > > +		 */
> > > +		parent = pci_upstream_bridge(p);
> > > +		chip->bus.keep_power = parent ? !pci_pr3_present(parent) : 1;
> > >    		chip->driver_caps |= AZX_DCAPS_PM_RUNTIME;
> > >    		pci_dev_put(p);
> > >    	}
> >
> >
> > --
> > Jaroslav Kysela <perex@xxxxxxxx>
> > Linux Sound Maintainer; ALSA Project; Red Hat, Inc.


--
Jaroslav Kysela <perex@xxxxxxxx>
Linux Sound Maintainer; ALSA Project; Red Hat, Inc.