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From:   Bin Meng <bmeng.cn@gmail.com>
Date:   Thu, 27 Sep 2018 10:10:07 +0800
Message-ID: <CAEUhbmXc--Ph71DGu2b+ijTzB6xvHXzuESBJKp9zARE2gjqV6w@mail.gmail.com>
Subject: Re: [PATCH] pci: Add a few new IDs for Intel GPU "spurious interrupt" quirk
To:     helgaas@kernel.org
Cc:     Bjorn Helgaas <bhelgaas@google.com>,
        linux-pci <linux-pci@vger.kernel.org>,
        Thomas Jarosch <thomas.jarosch@intra2net.com>,
        stable <stable@vger.kernel.org>, jani.nikula@linux.intel.com,
        joonas.lahtinen@linux.intel.com, rodrigo.vivi@intel.com,
        intel-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org,
        linux-kernel <linux-kernel@vger.kernel.org>
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Sender: linux-kernel-owner@vger.kernel.org
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Hi Bjorn,

On Thu, Sep 27, 2018 at 12:57 AM Bjorn Helgaas <helgaas@kernel.org> wrote:
>
> [+cc Intel DRM maintainers, etc]
>
> On Wed, Sep 26, 2018 at 08:14:01AM -0700, Bin Meng wrote:
> > Add more PCI IDs to the Intel GPU "spurious interrupt" quirk table,
> > which are known to break.
>
> Do you have a reference for this?  Any public bug reports, bugzilla,
> Intel spec reference or errata?  "Which are known to break" is pretty
> vague.
>

Sorry I used wrong words and should have been clearer. These devices
are validated to be broken. The test I used is very simple, just
unplug the VGA cable and plug it again, and "spurious interrupt" will
be seen on the interrupt line of the IGD device. I was not aware of
any public bugs filed to Intel, nor seen any errata from Intel.

> > See commit f67fd55fa96f ("PCI: Add quirk for still enabled interrupts
> > on Intel Sandy Bridge GPUs"), and commit 7c82126a94e6 ("PCI: Add new
> > ID for Intel GPU "spurious interrupt" quirk") for some history.
> >
> > Based on current findings, it is highly possible that all Intel
> > 1st/2nd/3rd generation Core processors' IGD has such quirk.
>
> Can you include a reference to these "current findings"?  I assume you
> have bug reports that include the device IDs you're adding?  If not,
> how did you build this list of new IDs?
>

By "current findings" I mean given the IDs we have here, plus previous
one added by Thomas, it's highly possible this VGA BIOS bug exists in
every 1st/2nd/3rd generation Core processors.

> The function comment added by f67fd55fa96f ("PCI: Add quirk for still
> enabled interrupts on Intel Sandy Bridge GPUs") suggests that this is
> actually a BIOS issue, not a hardware erratum, i.e., I don't see
> anything there that suggests a hardware defect.
>
> But there must be a hole somewhere -- the kernel can't be expected to
> disable interrupts in device-specific ways when there's no driver
> loaded.  Maybe it's simply a BIOS defect or maybe there's some
> interrupt or _PRT-related setup we're missing.
>

It's a pure VGA BIOS bug, not the BIOS bug or _PRT etc. The VGA BIOS
forgot to turn off the interrupt on these devices.

> > Signed-off-by: Bin Meng <bmeng.cn@gmail.com>
> > Cc: <stable@vger.kernel.org> # v3.4+
> > ---
> >
> >  drivers/pci/quirks.c | 4 ++++
> >  1 file changed, 4 insertions(+)
> >
> > diff --git a/drivers/pci/quirks.c b/drivers/pci/quirks.c
> > index 6bc27b7..c0673a7 100644
> > --- a/drivers/pci/quirks.c
> > +++ b/drivers/pci/quirks.c
> > @@ -3190,7 +3190,11 @@ static void disable_igfx_irq(struct pci_dev *dev)
> >
> >       pci_iounmap(dev, regs);
> >  }
> > +DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_INTEL, 0x0042, disable_igfx_irq);
> > +DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_INTEL, 0x0046, disable_igfx_irq);
> > +DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_INTEL, 0x004a, disable_igfx_irq);
> >  DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_INTEL, 0x0102, disable_igfx_irq);
> > +DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_INTEL, 0x0106, disable_igfx_irq);
> >  DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_INTEL, 0x010a, disable_igfx_irq);
> >  DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_INTEL, 0x0152, disable_igfx_irq);
> >
> > --

Regards,
Bin