linux-kernel - Re: [PATCH v6 2/3] PCI/AER: Disable AER interrupt on suspend

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Message-ID: <CAAd53p5WkzydfLAkMa6Dgt5vS0w5FHATfoDj3f=YkK-hPgJ+vQ@mail.gmail.com>
Date:   Wed, 9 Aug 2023 13:27:31 +0800
From:   Kai-Heng Feng <kai.heng.feng@...onical.com>
To:     Bjorn Helgaas <helgaas@...nel.org>
Cc:     bhelgaas@...gle.com, sathyanarayanan.kuppuswamy@...ux.intel.com,
        linuxppc-dev@...ts.ozlabs.org,
        Mahesh J Salgaonkar <mahesh@...ux.ibm.com>,
        linux-kernel@...r.kernel.org, koba.ko@...onical.com,
        "Oliver O'Halloran" <oohall@...il.com>, linux-pci@...r.kernel.org,
        mika.westerberg@...ux.intel.com,
        "Rafael J. Wysocki" <rjw@...ysocki.net>
Subject: Re: [PATCH v6 2/3] PCI/AER: Disable AER interrupt on suspend

On Fri, Jul 21, 2023 at 11:58 AM Kai-Heng Feng
<kai.heng.feng@...onical.com> wrote:
>
> On Tue, Jul 18, 2023 at 7:17 PM Bjorn Helgaas <helgaas@...nel.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 interrupt
> > > 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.

We are seeing another case where the issue happens on D3hot [0].
So I wonder if it's possible to disable AER unconditionally?

[0] https://bugzilla.kernel.org/show_bug.cgi?id=216295#c3

>
> Kai-Heng
>
> >
> > > As Per PCIe Base Spec 5.0, section 5.2, titled "Link State Power Management",
> > > 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 process
> > > should not affect the basic functionality.
> > >
> > > Link: https://bugzilla.kernel.org/show_bug.cgi?id=216295
> > > Reviewed-by: Mika Westerberg <mika.westerberg@...ux.intel.com>
> > > Signed-off-by: Kai-Heng Feng <kai.heng.feng@...onical.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 = get_service_data(dev);
> > > +     struct pci_dev *pdev = rpc->rpd;
> > > +
> > > +     aer_disable_irq(pdev);
> > > +
> > > +     return 0;
> > > +}
> > > +
> > > +static int aer_resume(struct pcie_device *dev)
> > > +{
> > > +     struct aer_rpc *rpc = get_service_data(dev);
> > > +     struct pci_dev *pdev = 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 = {
> > >       .service        = PCIE_PORT_SERVICE_AER,
> > >
> > >       .probe          = aer_probe,
> > > +     .suspend        = aer_suspend,
> > > +     .resume         = aer_resume,
> > >       .remove         = aer_remove,
> > >  };
> > >
> > > --
> > > 2.34.1
> > >