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

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Date:   Wed, 11 Dec 2019 05:58:26 +1000
From:   Dave Airlie <airlied@...il.com>
To:     "Rafael J. Wysocki" <rafael@...nel.org>
Cc:     Karol Herbst <kherbst@...hat.com>, Lyude Paul <lyude@...hat.com>,
        Mika Westerberg <mika.westerberg@...el.com>,
        Bjorn Helgaas <helgaas@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        "Rafael J . Wysocki" <rjw@...ysocki.net>,
        Linux PCI <linux-pci@...r.kernel.org>,
        Linux PM <linux-pm@...r.kernel.org>,
        dri-devel <dri-devel@...ts.freedesktop.org>,
        nouveau <nouveau@...ts.freedesktop.org>,
        Mario Limonciello <Mario.Limonciello@...l.com>
Subject: Re: [PATCH v4] pci: prevent putting nvidia GPUs into lower device
 states on certain intel bridges

On Mon, 9 Dec 2019 at 21:39, Rafael J. Wysocki <rafael@...nel.org> wrote:
>
> On Mon, Dec 9, 2019 at 12:17 PM Karol Herbst <kherbst@...hat.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.