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

[Karol Herbst]

On Fri, Nov 22, 2019 at 10:07 AM Rafael J. Wysocki <rafael at kernel.org> wrote:
>
> On Fri, Nov 22, 2019 at 1:13 AM Karol Herbst <kherbst at redhat.com> wrote:
> >
> > so while trying to test with d3cold disabled, I noticed that I run
> > into the exact same error.
>
> Does this mean that you disabled d3cold on the GPU via sysfs (the
> "d3cold_allowed" attribute was 0) and the original problem still
> occurred in that configuration?
>

yes. In my previous testing I was poking into the PCI registers of the
bridge controller and the GPU directly and that never caused any
issues as long as I limited it to putting the devices into D3hot.

> > And I verified that the
> > \_SB.PCI0.PEG0.PG00._STA returns 1, which indicates it should still be
> > turned on.
>
> I don't really understand this comment, so can you explain it a bit to
> me, please?
>

that's the ACPI method to fetch the "status" of the power resource, it
should return 0 when the device was powered off (the GPU) and 1
otherwise.