Re: [PATCH v5 2/3] PCI/AER: Disable AER interrupt on suspend

[Kai-Heng Feng <kai.heng.feng@canonical.com>]

On Fri, May 12, 2023 at 6:08 AM Sathyanarayanan Kuppuswamy
<sathyanarayanan.kuppuswamy@linux.intel.com> wrote:
>
>
>
> On 5/11/23 6:36 AM, Kai-Heng Feng wrote:
> > PCIe service that shares IRQ with PME may cause spurious wakeup on
> > system suspend.
> >
> > This is very similar to previous attempts to suspend AER and DPC [1],
> > but this time disabling AER IRQ is to prevent immediate PME wakeup when
> > AER shares the same IRQ line with PME.
>
> IMHO, you don't need to mention the previous submission reason.

Sure, will remove it in next revision.

>
> >
> > It's okay to disable AER because 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), hence we don't lose much here to disable AER IRQ during
> > system suspend.
>
> May be something like below?
>
> 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.
>
> 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.

I'll shamelessly use this in the commit message :)

Kai-Heng

>
> >
> > [1] https://lore.kernel.org/linux-pci/20220408153159.106741-1-kai.heng.feng@canonical.com/
> > Link: https://bugzilla.kernel.org/show_bug.cgi?id=216295
> >
> > Reviewed-by: Mika Westerberg <mika.westerberg@linux.intel.com>
> > Signed-off-by: Kai-Heng Feng <kai.heng.feng@canonical.com>
> > ---
> > 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,
> >  };
> >
>
> --
> Sathyanarayanan Kuppuswamy
> Linux Kernel Developer