Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
Date:   Wed, 16 Oct 2019 16:37:22 -0500
From:   Bjorn Helgaas <helgaas@kernel.org>
To:     Karol Herbst <kherbst@redhat.com>,
        "Rafael J . Wysocki" <rjw@rjwysocki.net>
Cc:     LKML <linux-kernel@vger.kernel.org>, Lyude Paul <lyude@redhat.com>,
        Mika Westerberg <mika.westerberg@intel.com>,
        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>,
        linux-acpi@vger.kernel.org
Subject: Re: [PATCH v3] pci: prevent putting nvidia GPUs into lower device
 states on certain intel bridges
Message-ID: <20191016213722.GA72810@google.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <CACO55ttOJaXKWmKQQbMAQRJHLXF-VtNn58n4BZhFKYmAdfiJjA@mail.gmail.com>
User-Agent: Mutt/1.10.1 (2018-07-13)
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

[+cc linux-acpi]

On Wed, Oct 16, 2019 at 09:18:32PM +0200, Karol Herbst wrote:
> but setting the PCI_DEV_FLAGS_NO_D3 flag does prevent using the
> platform means of putting the device into D3cold, right? That's
> actually what should still happen, just the D3hot step should be
> skipped.

If I understand correctly, when we put a device in D3cold on an ACPI
system, we do something like this:

  pci_set_power_state(D3cold)
    if (PCI_DEV_FLAGS_NO_D3)
      return 0                                   <-- nothing at all if quirked
    pci_raw_set_power_state
      pci_write_config_word(PCI_PM_CTRL, D3hot)  <-- set to D3hot
    __pci_complete_power_transition(D3cold)
      pci_platform_power_transition(D3cold)
        platform_pci_set_power_state(D3cold)
          acpi_pci_set_power_state(D3cold)
            acpi_device_set_power(ACPI_STATE_D3_COLD)
              ...
                acpi_evaluate_object("_OFF")     <-- set to D3cold

I did not understand the connection with platform (ACPI) power
management from your patch.  It sounds like you want this entire path
except that you want to skip the PCI_PM_CTRL write?

That seems like something Rafael should weigh in on.  I don't know
why we set the device to D3hot with PCI_PM_CTRL before using the ACPI
methods, and I don't know what the effect of skipping that is.  It
seems a little messy to slice out this tiny piece from the middle, but
maybe it makes sense.

> On Wed, Oct 16, 2019 at 9:14 PM Bjorn Helgaas <helgaas@kernel.org> wrote:
> >
> > On Wed, Oct 16, 2019 at 04:44:49PM +0200, Karol Herbst wrote:
> > > Fixes state transitions of Nvidia Pascal GPUs from D3cold into higher device
> > > states.
> > >
> > > v2: convert to pci_dev quirk
> > >     put a proper technical explanation of the issue as a in-code comment
> > > v3: disable it only for certain combinations of intel and nvidia hardware
> > >
> > > Signed-off-by: Karol Herbst <kherbst@redhat.com>
> > > Cc: Bjorn Helgaas <bhelgaas@google.com>
> > > Cc: Lyude Paul <lyude@redhat.com>
> > > Cc: Rafael J. Wysocki <rjw@rjwysocki.net>
> > > Cc: Mika Westerberg <mika.westerberg@intel.com>
> > > Cc: linux-pci@vger.kernel.org
> > > Cc: linux-pm@vger.kernel.org
> > > Cc: dri-devel@lists.freedesktop.org
> > > Cc: nouveau@lists.freedesktop.org
> > > ---
> > >  drivers/pci/pci.c    | 11 ++++++++++
> > >  drivers/pci/quirks.c | 52 ++++++++++++++++++++++++++++++++++++++++++++
> > >  include/linux/pci.h  |  1 +
> > >  3 files changed, 64 insertions(+)
> > >
> > > diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
> > > index b97d9e10c9cc..8e056eb7e6ff 100644
> > > --- a/drivers/pci/pci.c
> > > +++ b/drivers/pci/pci.c
> > > @@ -805,6 +805,13 @@ static inline bool platform_pci_bridge_d3(struct pci_dev *dev)
> > >       return pci_platform_pm ? pci_platform_pm->bridge_d3(dev) : false;
> > >  }
> > >
> > > +static inline bool parent_broken_child_pm(struct pci_dev *dev)
> > > +{
> > > +     if (!dev->bus || !dev->bus->self)
> > > +             return false;
> > > +     return dev->bus->self->broken_nv_runpm && dev->broken_nv_runpm;
> > > +}
> > > +
> > >  /**
> > >   * pci_raw_set_power_state - Use PCI PM registers to set the power state of
> > >   *                        given PCI device
> > > @@ -850,6 +857,10 @@ static int pci_raw_set_power_state(struct pci_dev *dev, pci_power_t state)
> > >          || (state == PCI_D2 && !dev->d2_support))
> > >               return -EIO;
> > >
> > > +     /* check if the bus controller causes issues */
> > > +     if (state != PCI_D0 && parent_broken_child_pm(dev))
> > > +             return 0;
> > > +
> > >       pci_read_config_word(dev, dev->pm_cap + PCI_PM_CTRL, &pmcsr);
> > >
> > >       /*
> > > diff --git a/drivers/pci/quirks.c b/drivers/pci/quirks.c
> > > index 44c4ae1abd00..c2f20b745dd4 100644
> > > --- a/drivers/pci/quirks.c
> > > +++ b/drivers/pci/quirks.c
> > > @@ -5268,3 +5268,55 @@ static void quirk_reset_lenovo_thinkpad_p50_nvgpu(struct pci_dev *pdev)
> > >  DECLARE_PCI_FIXUP_CLASS_FINAL(PCI_VENDOR_ID_NVIDIA, 0x13b1,
> > >                             PCI_CLASS_DISPLAY_VGA, 8,
> > >                             quirk_reset_lenovo_thinkpad_p50_nvgpu);
> > > +
> > > +/*
> > > + * Some Intel PCIe bridges cause devices to disappear from the PCIe bus after
> > > + * those were put into D3cold state if they were put into a non D0 PCI PM
> > > + * device state before doing so.
> > > + *
> > > + * This leads to various issue different issues which all manifest differently,
> > > + * but have the same root cause:
> > > + *  - AIML code execution hits an infinite loop (as the coe waits on device
> > > + *    memory to change).
> > > + *  - kernel crashes, as all pci reads return -1, which most code isn't able
> > > + *    to handle well enough.
> > > + *  - sudden shutdowns, as the kernel identified an unrecoverable error after
> > > + *    userspace tries to access the GPU.
> > > + *
> > > + * In all cases dmesg will contain at least one line like this:
> > > + * 'nouveau 0000:01:00.0: Refused to change power state, currently in D3'
> > > + * followed by a lot of nouveau timeouts.
> > > + *
> > > + * ACPI code writes bit 0x80 to the not documented PCI register 0x248 of the
> > > + * PCIe bridge controller in order to power down the GPU.
> > > + * Nonetheless, there are other code paths inside the ACPI firmware which use
> > > + * other registers, which seem to work fine:
> > > + *  - 0xbc bit 0x20 (publicly available documentation claims 'reserved')
> > > + *  - 0xb0 bit 0x10 (link disable)
> > > + * Changing the conditions inside the firmware by poking into the relevant
> > > + * addresses does resolve the issue, but it seemed to be ACPI private memory
> > > + * and not any device accessible memory at all, so there is no portable way of
> > > + * changing the conditions.
> > > + *
> > > + * The only systems where this behavior can be seen are hybrid graphics laptops
> > > + * with a secondary Nvidia Pascal GPU. It cannot be ruled out that this issue
> > > + * only occurs in combination with listed Intel PCIe bridge controllers and
> > > + * the mentioned GPUs or if it's only a hw bug in the bridge controller.
> > > + *
> > > + * But because this issue was NOT seen on laptops with an Nvidia Pascal GPU
> > > + * and an Intel Coffee Lake SoC, there is a higher chance of there being a bug
> > > + * in the bridge controller rather than in the GPU.
> > > + *
> > > + * This issue was not able to be reproduced on non laptop systems.
> > > + */
> > > +
> > > +static void quirk_broken_nv_runpm(struct pci_dev *dev)
> > > +{
> > > +     dev->broken_nv_runpm = 1;
> >
> > Can you use the existing PCI_DEV_FLAGS_NO_D3 flag for this instead of
> > adding a new flag?
> >
> > I would put the parent_broken_child_pm() logic here, if possible,
> > e.g., something like:
> >
> >   struct pci_dev *bridge = pci_upstream_bridge(dev);
> >
> >   if (bridge &&
> >       bridge->vendor == PCI_VENDOR_ID_INTEL && bridge->device == 0x1901)
> >         dev->dev_flags |= PCI_DEV_FLAGS_NO_D3;
> >
> > > +}
> > > +DECLARE_PCI_FIXUP_CLASS_FINAL(PCI_VENDOR_ID_NVIDIA, PCI_ANY_ID,
> > > +                           PCI_BASE_CLASS_DISPLAY, 16,
> > > +                           quirk_broken_nv_runpm);
> > > +/* kaby lake */
> > > +DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_INTEL, 0x1901,
> > > +                     quirk_broken_nv_runpm);
> > > diff --git a/include/linux/pci.h b/include/linux/pci.h
> > > index ac8a6c4e1792..903a0b3a39ec 100644
> > > --- a/include/linux/pci.h
> > > +++ b/include/linux/pci.h
> > > @@ -416,6 +416,7 @@ struct pci_dev {
> > >       unsigned int    __aer_firmware_first_valid:1;
> > >       unsigned int    __aer_firmware_first:1;
> > >       unsigned int    broken_intx_masking:1;  /* INTx masking can't be used */
> > > +     unsigned int    broken_nv_runpm:1;      /* some combinations of intel bridge controller and nvidia GPUs break rtd3 */
> > >       unsigned int    io_window_1k:1;         /* Intel bridge 1K I/O windows */
> > >       unsigned int    irq_managed:1;
> > >       unsigned int    has_secondary_link:1;
> > > --
> > > 2.21.0
> > >