[PATCH v4] pci: prevent putting nvidia GPUs into lower device states on certain intel bridges

[Rafael J. Wysocki]

On Thu, Nov 21, 2019 at 12:08 PM Rafael J. Wysocki <rafael at kernel.org> wrote:
>
> On Thu, Nov 21, 2019 at 12:03 PM Rafael J. Wysocki <rafael at kernel.org> wrote:
> >
> > On Thu, Nov 21, 2019 at 11:14 AM Mika Westerberg
> > <mika.westerberg at intel.com> wrote:
> > >
> > > On Wed, Nov 20, 2019 at 10:36:31PM +0100, Karol Herbst wrote:
> > > > with the branch and patch applied:
> > > > https://gist.githubusercontent.com/karolherbst/03c4c8141b0fa292d781badfa186479e/raw/5c62640afbc57d6e69ea924c338bd2836e770d02/gistfile1.txt
> > >
> > > Thanks for testing. Too bad it did not help :( I suppose there is no
> > > change if you increase the delay to say 1s?
> >
> > Well, look at the original patch in this thread.
> >
> > What it does is to prevent the device (GPU in this particular case)
> > from going into a PCI low-power state before invoking AML to power it
> > down (the AML is still invoked after this patch AFAICS), so why would
> > that have anything to do with the delays?
> >
> > The only reason would be the AML running too early, but that doesn't
> > seem likely.  IMO more likely is that the AML does something which
> > cannot be done to a device in a PCI low-power state.
>
> BTW, I'm wondering if anyone has tried to skip the AML instead of
> skipping the PCI PM in this case (as of 5.4-rc that would be a similar
> patch to skip the invocations of
> __pci_start/complete_power_transition() in pci_set_power_state() for
> the affected device).

Moving the dev->broken_nv_runpm test into
pci_platform_power_transition() (also for transitions into D0) would
be sufficient for that test if I'm not mistaken.