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From:   "Rafael J. Wysocki" <rafael@kernel.org>
Date:   Thu, 21 Nov 2019 12:15:17 +0100
Message-ID: <CAJZ5v0j515o9miy65MQkRURkw5bkFZxsva5pcgFW6Zfi+DE10Q@mail.gmail.com>
Subject: Re: [PATCH v4] pci: prevent putting nvidia GPUs into lower device
 states on certain intel bridges
To:     Mika Westerberg <mika.westerberg@intel.com>
Cc:     Karol Herbst <kherbst@redhat.com>,
        "Rafael J. Wysocki" <rafael@kernel.org>,
        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 Thu, Nov 21, 2019 at 12:08 PM Rafael J. Wysocki <rafael@kernel.org> wrote:
>
> On Thu, Nov 21, 2019 at 12:03 PM Rafael J. Wysocki <rafael@kernel.org> wrote:
> >
> > On Thu, Nov 21, 2019 at 11:14 AM Mika Westerberg
> > <mika.westerberg@intel.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).

Moving the dev->broken_nv_runpm test into
pci_platform_power_transition() (also for transitions into D0) would
be sufficient for that test if I'm not mistaken.