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

[Dave Airlie]

On Mon, 9 Dec 2019 at 21:39, Rafael J. Wysocki <rafael at kernel.org> wrote:
>
> On Mon, Dec 9, 2019 at 12:17 PM Karol Herbst <kherbst at redhat.com> wrote:
> >
> > anybody any other ideas?
>
> Not yet, but I'm trying to collect some more information.
>
> > It seems that both patches don't really fix
> > the issue and I have no idea left on my side to try out. The only
> > thing left I could do to further investigate would be to reverse
> > engineer the Nvidia driver as they support runpm on Turing+ GPUs now,
> > but I've heard users having similar issues to the one Lyude told us
> > about... and I couldn't verify that the patches help there either in a
> > reliable way.
>
> It looks like the newer (8+) versions of Windows expect the GPU driver
> to prepare the GPU for power removal in some specific way and the
> latter fails if the GPU has not been prepared as expected.
>
> Because testing indicates that the Windows 7 path in the platform
> firmware works, it may be worth trying to do what it does to the PCIe
> link before invoking the _OFF method for the power resource
> controlling the GPU power.
>

Remember the pre Win8 path required calling a DSM method to actually
power the card down, I think by the time we reach these methods in
those cases the card is already gone.

Dave.