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Date: Wed, 19 Jun 2024 14:05:26 +0800
From: Kai-Heng Feng <kai.heng.feng@...onical.com>
To: Bjorn Helgaas <helgaas@...nel.org>
Cc: bhelgaas@...gle.com, mahesh@...ux.ibm.com, oohall@...il.com,
linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org,
linuxppc-dev@...ts.ozlabs.org, bagasdotme@...il.com,
regressions@...ts.linux.dev, linux-nvme@...ts.infradead.org, kch@...dia.com,
hch@....de, gloriouseggroll@...il.com, kbusch@...nel.org, sagi@...mberg.me,
hare@...e.de
Subject: Re: [PATCH v8 2/3] PCI/AER: Disable AER service on suspend
On Wed, Jun 19, 2024 at 4:48 AM Bjorn Helgaas <helgaas@...nel.org> wrote:
>
> On Thu, Apr 25, 2024 at 03:33:01PM +0800, Kai-Heng Feng wrote:
> > On Fri, Apr 19, 2024 at 4:35 AM Bjorn Helgaas <helgaas@...nel.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@...onical.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.
>
> I think the issue is more likely on the resume side.
>
> aer_disable_rootport() disables AER interrupts, then clears
> PCI_ERR_ROOT_STATUS, so the path looks like this:
>
> aer_suspend
> aer_disable_rootport
> aer_disable_irq()
> pci_write_config_dword(PCI_ERR_ROOT_STATUS) # clear
>
> This happens during suspend, so at this point I think the link is
> still active and the spurious AER errors haven't happened yet and it
> probably doesn't matter that we clear PCI_ERR_ROOT_STATUS *here*.
>
> My guess is that what really matters is that we disable the AER
> interrupt so it doesn't happen during suspend, and then when we
> resume, we probably want to clear out the status registers before
> re-enabling the AER interrupt.
Thanks for catching this. Clearing status registers does the trick for
my cases here.
>
> In any event, I think we need to push this forward. I'll post a v9
> based on this but dropping the pci_ancestor_pr3_present(pdev) and
> pm_suspend_via_firmware() tests so we do this unconditionally.
Thanks for the v9.
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
> > > >
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