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

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Message-ID: <CACO55tvp6n2ahizwhc70xRJ1uTohs2ep962vwtHGQK-MkcLmsw@mail.gmail.com>
Date:   Mon, 21 Oct 2019 16:49:09 +0200
From:   Karol Herbst <kherbst@...hat.com>
To:     Mika Westerberg <mika.westerberg@...el.com>
Cc:     Bjorn Helgaas <helgaas@...nel.org>,
        "Rafael J . Wysocki" <rjw@...ysocki.net>,
        LKML <linux-kernel@...r.kernel.org>,
        Lyude Paul <lyude@...hat.com>,
        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>,
        Linux ACPI Mailing List <linux-acpi@...r.kernel.org>
Subject: Re: [PATCH v3] pci: prevent putting nvidia GPUs into lower device
 states on certain intel bridges

On Mon, Oct 21, 2019 at 4:09 PM Mika Westerberg
<mika.westerberg@...el.com> wrote:
>
> On Mon, Oct 21, 2019 at 03:54:09PM +0200, Karol Herbst wrote:
> > > I really would like to provide you more information about such
> > > workaround but I'm not aware of any ;-) I have not seen any issues like
> > > this when D3cold is properly implemented in the platform.  That's why
> > > I'm bit skeptical that this has anything to do with specific Intel PCIe
> > > ports. More likely it is some power sequence in the _ON/_OFF() methods
> > > that is run differently on Windows.
> >
> > yeah.. maybe. I really don't know what's the actual root cause. I just
> > know that with this workaround it works perfectly fine on my and some
> > other systems it was tested on. Do you know who would be best to
> > approach to get proper documentation about those methods and what are
> > the actual prerequisites of those methods?
>
> Those should be documented in the ACPI spec. Chapter 7 should explain
> power resources and the device power methods in detail.

either I looked up the wrong spec or the documentation isn't really
saying much there.