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

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Message-ID: <CAJZ5v0jjwaQpYR0P0TPPTGM-1zObm7w1y4bj=7MDvPL78jOz5w@mail.gmail.com>
Date:   Thu, 21 Nov 2019 12:08:31 +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 12:03 PM Rafael J. Wysocki <rafael@...nel.org> wrote:
>
> 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.

BTW, I'm wondering if anyone has tried to skip the AML instead of
skipping the PCI PM in this case (as of 5.4-rc that would be a similar
patch to skip the invocations of
__pci_start/complete_power_transition() in pci_set_power_state() for
the affected device).