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From:   Karol Herbst <kherbst@redhat.com>
Date:   Fri, 22 Nov 2019 12:30:52 +0100
Message-ID: <CACO55tue979AjxXO0MsOMVzUYvVaLh3rMDVg43=kqz=-OpW3Jw@mail.gmail.com>
Subject: Re: [PATCH v4] pci: prevent putting nvidia GPUs into lower device
 states on certain intel bridges
To:     "Rafael J. Wysocki" <rafael@kernel.org>
Cc:     Mika Westerberg <mika.westerberg@intel.com>,
        Bjorn Helgaas <helgaas@kernel.org>,
        LKML <linux-kernel@vger.kernel.org>,
        Lyude Paul <lyude@redhat.com>,
        "Rafael J . Wysocki" <rjw@rjwysocki.net>,
        Linux PCI <linux-pci@vger.kernel.org>,
        Linux PM <linux-pm@vger.kernel.org>,
        dri-devel <dri-devel@lists.freedesktop.org>,
        nouveau <nouveau@lists.freedesktop.org>,
        Dave Airlie <airlied@gmail.com>,
        Mario Limonciello <Mario.Limonciello@dell.com>
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On Fri, Nov 22, 2019 at 10:07 AM Rafael J. Wysocki <rafael@kernel.org> wrot=
e:
>
> On Fri, Nov 22, 2019 at 1:13 AM Karol Herbst <kherbst@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.