Re: [PATCH 0/5] PCI / igc: Improvements related to PTM enabling

Bjorn Helgaas
2026-02-24T17:13:09Z

On Tue, Feb 24, 2026 at 12:10:39PM +0100, Mika Westerberg wrote:
> Hi all,
>
> There is (still) an issue with Linux PCIe PTM enabling that happens because
> Linux automatically enables PTM if certain capabilities are set. However,
> turns out this is not enough because once we enumerate PCIe Switch Upstream
> port we also enable PTM but the Downstream Ports are not yet enumerated.
> This triggers floods of AER errors like this:
>
> pcieport 0000:00:07.1: AER: Multiple Uncorrectable (Non-Fatal) error message received from 0000:00:07.1
> pcieport 0000:00:07.1: PCIe Bus Error: severity=Uncorrectable (Non-Fatal), type=Transaction Layer, (Receiver ID)
> pcieport 0000:00:07.1: device [8086:d44f] error status/mask=00200000/00000000
> pcieport 0000:00:07.1: [21] ACSViol (First)
> pcieport 0000:00:07.1: AER: TLP Header: 0x34000000 0x00000052 0x00000000 0x00000000
> pcieport 0000:00:07.1: AER: device recovery successful
> pcieport 0000:00:07.1: AER: Uncorrectable (Non-Fatal) error message received from 0000:00:07.1
>
> We have ACS Source Validation enabled so Requester ID 0 which is sent by
> the not-enumerated Downstream Port triggers the ACS violation AER.
>
> This can be prevented by enabling PTM when the whole topology has been
> enumerated and doing it like that seems to be reasonable anyway because we
> only have a couple of drivers enabling it now so it does not make sense to
> enable otherwise as it consumes bandwidth.
>
> I did that fix and the problem went away but wanted to test with a device
> and driver that actually enables PTM. I have a couple of igc NICs here that
> has this support. However, when testing I noticed that during power state
> transitions we still get errors like this from igc:
>
> igc 0000:03:00.0 enp3s0: Timeout reading IGC_PTM_STAT register
>
> and after this PTM for the device stays disabled.
>
> This series includes fixes for igc that deal with the issues I found and
> now PTM gets succesfully enabled and works accross suspend and runtime
> suspend of igc, and there are no flood of AER errors as above. While there
> there is one cleanup patch in the middle that drops unused parameter.
>
> Mika Westerberg (5):
> igc: Call netif_queue_set_napi() with rntl locked
> igc: Let the PCI core deal with the PM resume flow
> igc: Don't reset the hardware on suspend path
> PCI/PTM: Drop granularity parameter from pci_enable_ptm()
> PCI/PTM: Do not enable PTM automatically for Root and Switch Upstream Ports

These last two don't look dependent on the igc patches, so I applied
them to pci/ptm for v7.1, thanks!

Let me know if there is some dependency and I can ack them and drop
them from the PCI tree.

> drivers/net/ethernet/intel/ice/ice_main.c | 2 +-
> drivers/net/ethernet/intel/idpf/idpf_main.c | 2 +-
> drivers/net/ethernet/intel/igc/igc.h | 2 +-
> drivers/net/ethernet/intel/igc/igc_ethtool.c | 6 +-
> drivers/net/ethernet/intel/igc/igc_main.c | 33 ++++----
> .../net/ethernet/mellanox/mlx5/core/main.c | 2 +-
> drivers/pci/pcie/ptm.c | 77 ++++++++++---------
> include/linux/pci.h | 6 +-
> 8 files changed, 64 insertions(+), 66 deletions(-)
>
> --
> 2.50.1
>