Date:   Wed, 20 Nov 2019 22:36:31 +0100
From:   Karol Herbst <kherbst@...hat.com>
To:     Mika Westerberg <mika.westerberg@...el.com>
Cc:     "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

with the branch and patch applied:
https://gist.githubusercontent.com/karolherbst/03c4c8141b0fa292d781badfa186479e/raw/5c62640afbc57d6e69ea924c338bd2836e770d02/gistfile1.txt

On Wed, Nov 20, 2019 at 5:23 PM Mika Westerberg
<mika.westerberg@...el.com> wrote:
>
> On Wed, Nov 20, 2019 at 05:53:07PM +0200, Mika Westerberg wrote:
> > On Wed, Nov 20, 2019 at 04:37:14PM +0100, Karol Herbst wrote:
> > > On Wed, Nov 20, 2019 at 4:15 PM Mika Westerberg
> > > <mika.westerberg@...el.com> wrote:
> > > >
> > > > On Wed, Nov 20, 2019 at 01:11:52PM +0100, Karol Herbst wrote:
> > > > > On Wed, Nov 20, 2019 at 1:09 PM Mika Westerberg
> > > > > <mika.westerberg@...el.com> wrote:
> > > > > >
> > > > > > On Wed, Nov 20, 2019 at 12:58:00PM +0100, Karol Herbst wrote:
> > > > > > > overall, what I really want to know is, _why_ does it work on windows?
> > > > > >
> > > > > > So do I ;-)
> > > > > >
> > > > > > > Or what are we doing differently on Linux so that it doesn't work? If
> > > > > > > anybody has any idea on how we could dig into this and figure it out
> > > > > > > on this level, this would probably allow us to get closer to the root
> > > > > > > cause? no?
> > > > > >
> > > > > > Have you tried to use the acpi_rev_override parameter in your system and
> > > > > > does it have any effect?
> > > > > >
> > > > > > Also did you try to trace the ACPI _ON/_OFF() methods? I think that
> > > > > > should hopefully reveal something.
> > > > > >
> > > > >
> > > > > I think I did in the past and it seemed to have worked, there is just
> > > > > one big issue with this: it's a Dell specific workaround afaik, and
> > > > > this issue plagues not just Dell, but we've seen it on HP and Lenovo
> > > > > laptops as well, and I've heard about users having the same issues on
> > > > > Asus and MSI laptops as well.
> > > >
> > > > Maybe it is not a workaround at all but instead it simply determines
> > > > whether the system supports RTD3 or something like that (IIRC Windows 8
> > > > started supporting it). Maybe Dell added check for Linux because at that
> > > > time Linux did not support it.
> > > >
> > >
> > > the point is, it's not checking it by default, so by default you still
> > > run into the windows 8 codepath.
> >
> > Well you can add the quirk to acpi_rev_dmi_table[] so it goes to that
> > path by default. There are a bunch of similar entries for Dell machines.
> >
> > Of course this does not help the non-Dell users so we would still need
> > to figure out the root cause.
>
> I think I asked you to test the PCIe delay patch and it did not help but
> I wonder if it helps if we increase the delay. As an experiment could
> you try Bjorn's pci/pm branch. The last two commits are for the delay.
>
> If you could pull that branch and apply the following patch on top and
> give it a try? Then post the dmesg somewhere so we can see whether it
> did the delay at all.
>
> diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
> index 1f319b1175da..1ad6f1372ed5 100644
> --- a/drivers/pci/pci.c
> +++ b/drivers/pci/pci.c
> @@ -4697,12 +4697,7 @@ void pci_bridge_wait_for_secondary_bus(struct pci_dev *dev)
>                 return;
>         }
>
> -       /* Take d3cold_delay requirements into account */
> -       delay = pci_bus_max_d3cold_delay(dev->subordinate);
> -       if (!delay) {
> -               up_read(&pci_bus_sem);
> -               return;
> -       }
> +       delay = 500;
>
>         child = list_first_entry(&dev->subordinate->devices, struct pci_dev,
>                                  bus_list);
> @@ -4715,7 +4710,7 @@ void pci_bridge_wait_for_secondary_bus(struct pci_dev *dev)
>          * management for them (see pci_bridge_d3_possible()).
>          */
>         if (!pci_is_pcie(dev)) {
> -               pci_dbg(dev, "waiting %d ms for secondary bus\n", 1000 + delay);
> +               pci_info(dev, "waiting %d ms for secondary bus\n", 1000 + delay);
>                 msleep(1000 + delay);
>                 return;
>         }
> @@ -4741,10 +4736,10 @@ void pci_bridge_wait_for_secondary_bus(struct pci_dev *dev)
>                 return;
>
>         if (pcie_get_speed_cap(dev) <= PCIE_SPEED_5_0GT) {
> -               pci_dbg(dev, "waiting %d ms for downstream link\n", delay);
> +               pci_info(dev, "waiting %d ms for downstream link\n", delay);
>                 msleep(delay);
>         } else {
> -               pci_dbg(dev, "waiting %d ms for downstream link, after activation\n",
> +               pci_info(dev, "waiting %d ms for downstream link, after activation\n",
>                         delay);
>                 if (!pcie_wait_for_link_delay(dev, true, delay)) {
>                         /* Did not train, no need to wait any further */
> @@ -4753,7 +4748,7 @@ void pci_bridge_wait_for_secondary_bus(struct pci_dev *dev)
>         }
>
>         if (!pci_device_is_present(child)) {
> -               pci_dbg(child, "waiting additional %d ms to become accessible\n", delay);
> +               pci_info(child, "waiting additional %d ms to become accessible\n", delay);
>                 msleep(delay);
>         }
>  }
>

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