Re: [Nouveau] [PATCH v2] drm: don't continue with anything after the GPU couldn't be woken up

[Thierry Reding <thierry.reding@gmail.com>]

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On Tue, Nov 21, 2017 at 08:03:20PM +0100, Karol Herbst wrote:
> On Tue, Nov 21, 2017 at 6:46 PM, Thierry Reding
> <thierry.reding@gmail.com> wrote:
> > On Tue, Nov 21, 2017 at 04:01:16PM +0100, Karol Herbst wrote:
> >> This should make systems more stable where resuming the GPU fails. This
> >> can happen due to bad firmware or due to a bug within the kernel. The
> >> last thing which should happen in either case is an unusable system.
> >>
> >> v2: do the same in nouveau_pmops_resume
> >>
> >> Tested-by: Karl Hastings <kazen@redhat.com>
> >> Signed-off-by: Karol Herbst <kherbst@redhat.com>
> >> ---
> >>  drm/nouveau/nouveau_drm.c | 31 +++++++++++++++++++++++--------
> >>  1 file changed, 23 insertions(+), 8 deletions(-)
> >>
> >> diff --git a/drm/nouveau/nouveau_drm.c b/drm/nouveau/nouveau_drm.c
> >> index 8d4a5be3..6e4cb4f7 100644
> >> --- a/drm/nouveau/nouveau_drm.c
> >> +++ b/drm/nouveau/nouveau_drm.c
> >> @@ -792,6 +792,27 @@ nouveau_pmops_suspend(struct device *dev)
> >>       return 0;
> >>  }
> >>
> >> +static int
> >> +nouveau_set_power_state_D0(struct pci_dev *pdev)
> >> +{
> >> +     struct nouveau_drm *drm = nouveau_drm(pci_get_drvdata(pdev));
> >> +     int ret;
> >> +
> >> +     pci_set_power_state(pdev, PCI_D0);
> >> +     /* abort if anything went wrong */
> >> +     if (pdev->current_state != PCI_D0) {
> >> +             NV_ERROR(drm, "couldn't wake up GPU!\n");
> >> +             return -EBUSY;
> >> +     }
> >
> > Looks to me like the more idiomatic way to do this is:
> >
> >         ret = pci_set_power_state(pdev, PCI_D0);
> >         if (ret < 0 && ret != -EIO)
> >                 return ret;
> >
> 
> I thought so too, but it ends up returning 0 even if setting the power
> state fails. Or maybe I did something wrong when installing the
> kernel. I could take another shot at it, but what I came up with seems
> to work. Adding airlied in CC, because he saw my patch and didn't
> complain about it. Hopefully he knows more.

pci_raw_set_power_state(), called by pci_set_power_state(), contains
this, which looks to me like it would be the only case where the problem
you're describing could be coming from:

	dev->current_state = (pmcsr & PCI_PM_CTRL_STATE_MASK);
	if (dev->current_state != state && printk_ratelimit())
		dev_info(&dev->dev, "Refused to change power state, currently in D%d\n",
			 dev->current_state);

Do you happen to see this in the kernel logs? Perhaps this should be
considered an error rather than just an KERN_INFO level message?

Adding Bjorn and linux-pci for visibility.

Thierry

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