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References: <20230512000014.118942-2-kai.heng.feng@canonical.com> <20230718111702.GA354713@bhelgaas>
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From:   Kai-Heng Feng <kai.heng.feng@canonical.com>
Date:   Fri, 21 Jul 2023 11:58:24 +0800
Message-ID: <CAAd53p7RfVcZjw+ShtkTmhCAA4zpegRZOzwiXgmanthx_KMjxA@mail.gmail.com>
Subject: Re: [PATCH v6 2/3] PCI/AER: Disable AER interrupt on suspend
To:     Bjorn Helgaas <helgaas@kernel.org>
Cc:     bhelgaas@google.com, sathyanarayanan.kuppuswamy@linux.intel.com,
        linuxppc-dev@lists.ozlabs.org,
        Mahesh J Salgaonkar <mahesh@linux.ibm.com>,
        linux-kernel@vger.kernel.org, koba.ko@canonical.com,
        "Oliver O'Halloran" <oohall@gmail.com>, linux-pci@vger.kernel.org,
        mika.westerberg@linux.intel.com,
        "Rafael J. Wysocki" <rjw@rjwysocki.net>
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On Tue, Jul 18, 2023 at 7:17=E2=80=AFPM Bjorn Helgaas <helgaas@kernel.org> =
wrote:
>
> [+cc Rafael]
>
> On Fri, May 12, 2023 at 08:00:13AM +0800, Kai-Heng Feng wrote:
> > PCIe services that share an IRQ with PME, such as AER or DPC, may cause=
 a
> > spurious wakeup on system suspend. To prevent this, disable the AER int=
errupt
> > notification during the system suspend process.
>
> I see that in this particular BZ dmesg log, PME, AER, and DPC do share
> the same IRQ, but I don't think this is true in general.
>
> Root Ports usually use MSI or MSI-X.  PME and hotplug events use the
> Interrupt Message Number in the PCIe Capability, but AER uses the one
> in the AER Root Error Status register, and DPC uses the one in the DPC
> Capability register.  Those potentially correspond to three distinct
> MSI/MSI-X vectors.
>
> I think this probably has nothing to do with the IRQ being *shared*,
> but just that putting the downstream component into D3cold, where the
> link state is L3, may cause the upstream component to log and signal a
> link-related error as the link goes completely down.

That's quite likely a better explanation than my wording.
Assuming AER IRQ and PME IRQ are not shared, does system get woken up
by AER IRQ?

>
> I don't think D0-D3hot should be relevant here because in all those
> states, the link should be active because the downstream config space
> remains accessible.  So I'm not sure if it's possible, but I wonder if
> there's a more targeted place we could do this, e.g., in the path that
> puts downstream devices in D3cold.

Let me try to work on this.

Kai-Heng

>
> > As Per PCIe Base Spec 5.0, section 5.2, titled "Link State Power Manage=
ment",
> > TLP and DLLP transmission are disabled for a Link in L2/L3 Ready (D3hot=
), L2
> > (D3cold with aux power) and L3 (D3cold) states. So disabling the AER
> > notification during suspend and re-enabling them during the resume proc=
ess
> > should not affect the basic functionality.
> >
> > 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>
> > ---
> > v6:
> > v5:
> >  - Wording.
> >
> > v4:
> > v3:
> >  - No change.
> >
> > v2:
> >  - Only disable AER IRQ.
> >  - No more check on PME IRQ#.
> >  - Use helper.
> >
> >  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,
> >  };
> >
> > --
> > 2.34.1
> >