[+cc Rajvi, David]
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
>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?
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).
Nit: can you remove the timestamps from the log? They add clutter but
no useful information.
[1] https://git.kernel.org/linus/a697f072f5da
> Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=215453
> Reviewed-by: Mika Westerberg <mika.westerb...@linux.intel.com>
> Signed-off-by: Kai-Heng Feng <kai.heng.f...@canonical.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
>
