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From:   Kai-Heng Feng <kai.heng.feng@canonical.com>
Date:   Tue, 25 Apr 2023 13:55:46 +0800
Message-ID: <CAAd53p5nrTQOxLkv+e9gLu3R9iOLXz5taJuwaAO4_W7_y89vEw@mail.gmail.com>
Subject: Re: [PATCH v4 2/3] PCI/AER: Disable AER interrupt on suspend
To:     Sathyanarayanan Kuppuswamy 
        <sathyanarayanan.kuppuswamy@linux.intel.com>
Cc:     bhelgaas@google.com, mika.westerberg@linux.intel.com,
        koba.ko@canonical.com, Mahesh J Salgaonkar <mahesh@linux.ibm.com>,
        "Oliver O'Halloran" <oohall@gmail.com>,
        linuxppc-dev@lists.ozlabs.org, linux-pci@vger.kernel.org,
        linux-kernel@vger.kernel.org
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On Tue, Apr 25, 2023 at 7:47=E2=80=AFAM Sathyanarayanan Kuppuswamy
<sathyanarayanan.kuppuswamy@linux.intel.com> wrote:
>
>
>
> On 4/23/23 10:52 PM, Kai-Heng Feng wrote:
> > PCIe service that shares IRQ with PME may cause spurious wakeup on
> > system suspend.
> >
> > PCIe Base Spec 5.0, section 5.2 "Link State Power Management" states
> > that TLP and DLLP transmission is disabled for a Link in L2/L3 Ready
> > (D3hot), L2 (D3cold with aux power) and L3 (D3cold), so we don't lose
> > much here to disable AER during system suspend.
> >
> > This is very similar to previous attempts to suspend AER and DPC [1],
> > but with a different reason.
> >
> > [1] https://lore.kernel.org/linux-pci/20220408153159.106741-1-kai.heng.=
feng@canonical.com/
> > Link: https://bugzilla.kernel.org/show_bug.cgi?id=3D216295
> >
> > Reviewed-by: Mika Westerberg <mika.westerberg@linux.intel.com>
> > Signed-off-by: Kai-Heng Feng <kai.heng.feng@canonical.com>
> > ---
>
> IIUC, you encounter AER errors during the suspend/resume process, which
> results in AER IRQ. Because AER and PME share an IRQ, it is regarded as a
> spurious wake-up IRQ. So to fix it, you want to disable AER reporting,
> right?

Yes. That's exactly what happened.

>
> It looks like it is harmless to disable the AER during the suspend/resume
> path. But, I am wondering why we get these errors? Did you check what err=
ors
> you get during the suspend/resume path? Are these errors valid?

I really don't know. I think it's similar to the reasoning in commit
b07461a8e45b ("PCI/AER: Clear error status registers during
enumeration and restore"): "AER errors might be recorded when
powering-on devices. These errors can be ignored, ...".
For this case, it happens when powering-off the device (D3cold) via
turning off power resources.

Kai-Heng

>
>
> >  drivers/pci/pcie/aer.c | 22 ++++++++++++++++++++++
> >  1 file changed, 22 insertions(+)
> >
> > diff --git a/drivers/pci/pcie/aer.c b/drivers/pci/pcie/aer.c
> > index 1420e1f27105..9c07fdbeb52d 100644
> > --- a/drivers/pci/pcie/aer.c
> > +++ b/drivers/pci/pcie/aer.c
> > @@ -1356,6 +1356,26 @@ static int aer_probe(struct pcie_device *dev)
> >       return 0;
> >  }
> >
> > +static int aer_suspend(struct pcie_device *dev)
> > +{
> > +     struct aer_rpc *rpc =3D get_service_data(dev);
> > +     struct pci_dev *pdev =3D rpc->rpd;
> > +
> > +     aer_disable_irq(pdev);
> > +
> > +     return 0;
> > +}
> > +
> > +static int aer_resume(struct pcie_device *dev)
> > +{
> > +     struct aer_rpc *rpc =3D get_service_data(dev);
> > +     struct pci_dev *pdev =3D rpc->rpd;
> > +
> > +     aer_enable_irq(pdev);
> > +
> > +     return 0;
> > +}
> > +
> >  /**
> >   * aer_root_reset - reset Root Port hierarchy, RCEC, or RCiEP
> >   * @dev: pointer to Root Port, RCEC, or RCiEP
> > @@ -1420,6 +1440,8 @@ static struct pcie_port_service_driver aerdriver =
=3D {
> >       .service        =3D PCIE_PORT_SERVICE_AER,
> >
> >       .probe          =3D aer_probe,
> > +     .suspend        =3D aer_suspend,
> > +     .resume         =3D aer_resume,
> >       .remove         =3D aer_remove,
> >  };
> >
>
> --
> Sathyanarayanan Kuppuswamy
> Linux Kernel Developer