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Date: Fri, 1 Jul 2022 12:06:46 +0800
From: Kai-Heng Feng <kai.heng.feng@...onical.com>
To: Bjorn Helgaas <helgaas@...nel.org>
Cc: bhelgaas@...gle.com, mika.westerberg@...ux.intel.com,
koba.ko@...onical.com, baolu.lu@...ux.intel.com,
sathyanarayanan.kuppuswamy@...ux.intel.com,
Russell Currey <ruscur@...sell.cc>,
"Oliver O'Halloran" <oohall@...il.com>,
linuxppc-dev@...ts.ozlabs.org, linux-pci@...r.kernel.org,
linux-kernel@...r.kernel.org,
Rajvi Jingar <rajvi.jingar@...el.com>,
david.e.box@...ux.intel.com,
"Rafael J. Wysocki" <rjw@...ysocki.net>, linux-pm@...r.kernel.org
Subject: Re: [PATCH v4 1/2] PCI/AER: Disable AER service when link is in L2/L3
ready, L2 and L3 state
On Sat, Apr 23, 2022 at 6:26 AM Bjorn Helgaas <helgaas@...nel.org> wrote:
>
> [+cc Rafael, linux-pm; sorry forgot this last time]
>
> On Fri, Apr 22, 2022 at 05:24:36PM -0500, Bjorn Helgaas wrote:
> > On Fri, Apr 08, 2022 at 11:31:58PM +0800, Kai-Heng Feng wrote:
> > > On Intel Alder Lake platforms, Thunderbolt entering D3cold can cause
> > > some errors reported by AER:
> > > [ 30.100211] pcieport 0000:00:1d.0: AER: Uncorrected (Non-Fatal) error received: 0000:00:1d.0
> > > [ 30.100251] pcieport 0000:00:1d.0: PCIe Bus Error: severity=Uncorrected (Non-Fatal), type=Transaction Layer, (Requester ID)
> > > [ 30.100256] pcieport 0000:00:1d.0: device [8086:7ab0] error status/mask=00100000/00004000
> > > [ 30.100262] pcieport 0000:00:1d.0: [20] UnsupReq (First)
> > > [ 30.100267] pcieport 0000:00:1d.0: AER: TLP Header: 34000000 08000052 00000000 00000000
> > > [ 30.100372] thunderbolt 0000:0a:00.0: AER: can't recover (no error_detected callback)
> > > [ 30.100401] xhci_hcd 0000:3e:00.0: AER: can't recover (no error_detected callback)
> > > [ 30.100427] pcieport 0000:00:1d.0: AER: device recovery failed
> > >
> > > So disable AER service to avoid the noises from turning power rails
> > > on/off when the device is in low power states (D3hot and D3cold), as
> > > 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).
> >
> > Help me walk through what's happening here, because I'm never very
> > confident about how error reporting works. I *think* the Unsupported
> > Request error means some request was in progress and was not
> > completed. I don't think a link going down should by itself cause
> > an Unsupported Request error because there's no *request*.
> >
> > I have a theory about what happened here. Decoding the TLP Header
> > (from PCIe r6.0, sec 2.2.1.1, 2.2.8.10) gives:
> >
> > 34000000 (0011 0100 ...):
> > Fmt 001 4 DW header, no data
> > Type 1 0100 Msg, Local - Terminate at Receiver
> >
> > 08000052 (0800 ... 0101 0010)
> > Requester ID 0800 00:08.0
> > Message Code 0101 0010 PTM Request
Is there any TLP decoder software available? That will be really
helpful for debugging.
> >
> > From your lspci in bugzilla, 08:00 has PTM enabled. So my theory is
> > that:
> >
> > - 08:00.0 sent a PTM Request Message (a Posted Request)
> > - 00:1d.0 received the PTM Request Message
> > - The link transitioned to DL_Down
> > - Per sec 2.9.1, 00:1d.0 discarded the Request and reported an
> > Unsupported Request
> > - Or, per sec 6.21.3, if 00:1d.0 received a PTM Request when its
> > own PTM Enable was clear, it would also be treated as an
> > Unsupported Request
> >
> > So I suspect we should disable PTM on 08:00.0 before putting it in a
> > low-power state. If you manually disable PTM on 08:00.0, do these
> > errors stop happening?
Yes, disabling PTM on upstream port can solve the issue.
Thanks for find the root cause!
> >
> > David did something like this [1], but just for Root Ports. That
> > looks wrong to me because sec 6.21.3 says we should not have PTM
> > enabled in an Upstream Port (i.e., in a downstream device like
> > 08:00.0) unless it is already enabled in the Downstream Port (i.e., in
> > the Root Port 00:1d.0).
So I think it should be like this?
diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index cfaf40a540a82..8ba8a0e12946e 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -2717,7 +2717,8 @@ int pci_prepare_to_sleep(struct pci_dev *dev)
* port to enter a lower-power PM state and the SoC to reach a
* lower-power idle state as a whole.
*/
- if (pci_pcie_type(dev) == PCI_EXP_TYPE_ROOT_PORT)
+ if (pci_pcie_type(dev) == PCI_EXP_TYPE_ROOT_PORT ||
+ pci_pcie_type(dev) == PCI_EXP_TYPE_UPSTREAM)
pci_disable_ptm(dev);
pci_enable_wake(dev, target_state, wakeup);
@@ -2775,7 +2776,8 @@ int pci_finish_runtime_suspend(struct pci_dev *dev)
* port to enter a lower-power PM state and the SoC to reach a
* lower-power idle state as a whole.
*/
- if (pci_pcie_type(dev) == PCI_EXP_TYPE_ROOT_PORT)
+ if (pci_pcie_type(dev) == PCI_EXP_TYPE_ROOT_PORT ||
+ pci_pcie_type(dev) == PCI_EXP_TYPE_UPSTREAM)
pci_disable_ptm(dev);
__pci_enable_wake(dev, target_state, pci_dev_run_wake(dev));
> >
> > Nit: can you remove the timestamps from the log? They add clutter but
> > no useful information.
Sure.
> >
> > [1] https://git.kernel.org/linus/a697f072f5da
> >
> > > Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=215453
> > > Reviewed-by: Mika Westerberg <mika.westerberg@...ux.intel.com>
> > > Signed-off-by: Kai-Heng Feng <kai.heng.feng@...onical.com>
> > > ---
> > > v4:
> > > - Explicitly states the spec version.
> > > - Wording change.
> > >
> > > v3:
> > > - Remove reference to ACS.
> > > - Wording change.
> > >
> > > v2:
> > > - Wording change.
> > >
> > > drivers/pci/pcie/aer.c | 31 +++++++++++++++++++++++++------
> > > 1 file changed, 25 insertions(+), 6 deletions(-)
> > >
> > > diff --git a/drivers/pci/pcie/aer.c b/drivers/pci/pcie/aer.c
> > > index 9fa1f97e5b270..e4e9d4a3098d7 100644
> > > --- a/drivers/pci/pcie/aer.c
> > > +++ b/drivers/pci/pcie/aer.c
> > > @@ -1367,6 +1367,22 @@ 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);
> > > +
> > > + aer_disable_rootport(rpc);
> > > + return 0;
> > > +}
> > > +
> > > +static int aer_resume(struct pcie_device *dev)
> > > +{
> > > + struct aer_rpc *rpc = get_service_data(dev);
> > > +
> > > + aer_enable_rootport(rpc);
> > > + return 0;
> > > +}
> > > +
> > > /**
> > > * aer_root_reset - reset Root Port hierarchy, RCEC, or RCiEP
> > > * @dev: pointer to Root Port, RCEC, or RCiEP
> > > @@ -1433,12 +1449,15 @@ static pci_ers_result_t aer_root_reset(struct pci_dev *dev)
> > > }
> > >
> > > static struct pcie_port_service_driver aerdriver = {
> > > - .name = "aer",
> > > - .port_type = PCIE_ANY_PORT,
> > > - .service = PCIE_PORT_SERVICE_AER,
> > > -
> > > - .probe = aer_probe,
> > > - .remove = aer_remove,
> > > + .name = "aer",
> > > + .port_type = PCIE_ANY_PORT,
> > > + .service = PCIE_PORT_SERVICE_AER,
> > > + .probe = aer_probe,
> > > + .suspend = aer_suspend,
> > > + .resume = aer_resume,
> > > + .runtime_suspend = aer_suspend,
> > > + .runtime_resume = aer_resume,
> > > + .remove = aer_remove,
> > > };
> > >
> > > /**
> > > --
> > > 2.34.1
> > >
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