linux-kernel - Re: [PATCH v3] pci: prevent putting nvidia GPUs into lower device states on certain intel bridges

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Date:   Mon, 21 Oct 2019 15:02:23 +0200
From:   Karol Herbst <kherbst@...hat.com>
To:     Mika Westerberg <mika.westerberg@...el.com>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Lyude Paul <lyude@...hat.com>,
        "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>
Subject: Re: [PATCH v3] pci: prevent putting nvidia GPUs into lower device
 states on certain intel bridges

On Mon, Oct 21, 2019 at 2:06 PM Mika Westerberg
<mika.westerberg@...el.com> wrote:
>
> On Mon, Oct 21, 2019 at 02:00:46PM +0200, Karol Herbst wrote:
> > On Mon, Oct 21, 2019 at 1:40 PM Mika Westerberg
> > <mika.westerberg@...el.com> wrote:
> > >
> > > Hi Karol,
> > >
> > > Sorry for commenting late, I just came back from vacation.
> > >
> > > On Wed, Oct 16, 2019 at 04:44:49PM +0200, Karol Herbst wrote:
> > > > Fixes state transitions of Nvidia Pascal GPUs from D3cold into higher device
> > > > states.
> > > >
> > > > v2: convert to pci_dev quirk
> > > >     put a proper technical explanation of the issue as a in-code comment
> > > > v3: disable it only for certain combinations of intel and nvidia hardware
> > > >
> > > > Signed-off-by: Karol Herbst <kherbst@...hat.com>
> > > > Cc: Bjorn Helgaas <bhelgaas@...gle.com>
> > > > Cc: Lyude Paul <lyude@...hat.com>
> > > > Cc: Rafael J. Wysocki <rjw@...ysocki.net>
> > > > Cc: Mika Westerberg <mika.westerberg@...el.com>
> > > > Cc: linux-pci@...r.kernel.org
> > > > Cc: linux-pm@...r.kernel.org
> > > > Cc: dri-devel@...ts.freedesktop.org
> > > > Cc: nouveau@...ts.freedesktop.org
> > > > ---
> > > >  drivers/pci/pci.c    | 11 ++++++++++
> > > >  drivers/pci/quirks.c | 52 ++++++++++++++++++++++++++++++++++++++++++++
> > >
> > > I may be missing something but why you can't do this in the nouveau
> > > driver itself?
> >
> > What do you mean precisely? Move the quirk into nouveau, but keep the
> > changes to pci core?
>
> No, just block runtime PM from the device in nouveau driver.

but that's not what the patch does. It only skips the PCI PM reg
write, but still let the ACPI method be invoked to put the device into
D3cold