Re: [PATCH v8 2/3] PCI/AER: Disable AER service on suspend

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

On Fri, Apr 19, 2024 at 4:35 AM Bjorn Helgaas <helgaas@kernel.org> wrote:
>
> On Tue, Apr 16, 2024 at 12:32:24PM +0800, Kai-Heng Feng wrote:
> > When the power rail gets cut off, the hardware can create some electric
> > noise on the link that triggers AER. If IRQ is shared between AER with
> > PME, such AER noise will cause a spurious wakeup on system suspend.
> >
> > When the power rail gets back, the firmware of the device resets itself
> > and can create unexpected behavior like sending PTM messages. For this
> > case, the driver will always be too late to toggle off features should
> > be disabled.
> >
> > 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 if
> > the power will be turned off during suspend process, disable AER service
> > and re-enable it during the resume process. This should not affect the
> > basic functionality.
> >
> > Link: https://bugzilla.kernel.org/show_bug.cgi?id=209149
> > Link: https://bugzilla.kernel.org/show_bug.cgi?id=216295
> > Link: https://bugzilla.kernel.org/show_bug.cgi?id=218090
> > Signed-off-by: Kai-Heng Feng <kai.heng.feng@canonical.com>
>
> Thanks for reviving this series.  I tried follow the history about
> this, but there are at least two series that were very similar and I
> can't put it all together.
>
> > ---
> > v8:
> >  - Add more bug reports.
> >
> > v7:
> >  - Wording
> >  - Disable AER completely (again) if power will be turned off
> >
> > 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 | 25 +++++++++++++++++++++++++
> >  1 file changed, 25 insertions(+)
> >
> > diff --git a/drivers/pci/pcie/aer.c b/drivers/pci/pcie/aer.c
> > index ac6293c24976..bea7818c2d1b 100644
> > --- a/drivers/pci/pcie/aer.c
> > +++ b/drivers/pci/pcie/aer.c
> > @@ -28,6 +28,7 @@
> >  #include <linux/delay.h>
> >  #include <linux/kfifo.h>
> >  #include <linux/slab.h>
> > +#include <linux/suspend.h>
> >  #include <acpi/apei.h>
> >  #include <acpi/ghes.h>
> >  #include <ras/ras_event.h>
> > @@ -1497,6 +1498,28 @@ 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;
> > +
> > +     if (pci_ancestor_pr3_present(pdev) || pm_suspend_via_firmware())
> > +             aer_disable_rootport(rpc);
>
> Why do we check pci_ancestor_pr3_present(pdev) and
> pm_suspend_via_firmware()?  I'm getting pretty convinced that we need
> to disable AER interrupts on suspend in general.  I think it will be
> better if we do that consistently on all platforms, not special cases
> based on details of how we suspend.

Sure. Will change in next revision.

>
> Also, why do we use aer_disable_rootport() instead of just
> aer_disable_irq()?  I think it's the interrupt that causes issues on
> suspend.  I see that there *were* some versions that used
> aer_disable_irq(), but I can't find the reason it changed.

Interrupt can cause system wakeup, if it's shared with PME.

The reason why aer_disable_rootport() is used over aer_disable_irq()
is that when the latter is used the error still gets logged during
sleep cycle. Once the pcieport driver resumes, it invokes
aer_root_reset() to reset the hierarchy, while the hierarchy hasn't
resumed yet.

So use aer_disable_rootport() to prevent such issue from happening.

Kai-Heng

>
> > +
> > +     return 0;
> > +}
> > +
> > +static int aer_resume(struct pcie_device *dev)
> > +{
> > +     struct aer_rpc *rpc = get_service_data(dev);
> > +     struct pci_dev *pdev = rpc->rpd;
> > +
> > +     if (pci_ancestor_pr3_present(pdev) || pm_resume_via_firmware())
> > +             aer_enable_rootport(rpc);
> > +
> > +     return 0;
> > +}
> > +
> >  /**
> >   * aer_root_reset - reset Root Port hierarchy, RCEC, or RCiEP
> >   * @dev: pointer to Root Port, RCEC, or RCiEP
> > @@ -1561,6 +1584,8 @@ 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
> >