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

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Message-ID: <CAJZ5v0hAgz4Fu=83AJE2PYUsi+Jk=Lrr4MNp5ySA9yY=3wr5rg@mail.gmail.com>
Date:   Thu, 21 Nov 2019 12:03:52 +0100
From:   "Rafael J. Wysocki" <rafael@...nel.org>
To:     Mika Westerberg <mika.westerberg@...el.com>
Cc:     Karol Herbst <kherbst@...hat.com>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Bjorn Helgaas <helgaas@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        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>,
        Dave Airlie <airlied@...il.com>,
        Mario Limonciello <Mario.Limonciello@...l.com>
Subject: Re: [PATCH v4] pci: prevent putting nvidia GPUs into lower device
 states on certain intel bridges

On Thu, Nov 21, 2019 at 11:14 AM Mika Westerberg
<mika.westerberg@...el.com> wrote:
>
> On Wed, Nov 20, 2019 at 10:36:31PM +0100, Karol Herbst wrote:
> > with the branch and patch applied:
> > https://gist.githubusercontent.com/karolherbst/03c4c8141b0fa292d781badfa186479e/raw/5c62640afbc57d6e69ea924c338bd2836e770d02/gistfile1.txt
>
> Thanks for testing. Too bad it did not help :( I suppose there is no
> change if you increase the delay to say 1s?

Well, look at the original patch in this thread.

What it does is to prevent the device (GPU in this particular case)
from going into a PCI low-power state before invoking AML to power it
down (the AML is still invoked after this patch AFAICS), so why would
that have anything to do with the delays?

The only reason would be the AML running too early, but that doesn't
seem likely.  IMO more likely is that the AML does something which
cannot be done to a device in a PCI low-power state.