Re: [PATCH 3/3] e1000e: Serialize TGP e1000e PM ops

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

Hi Sasha,

On Mon, Jul 12, 2021 at 9:35 PM Kai-Heng Feng
<kai.heng.feng@canonical.com> wrote:
>
> On TGL systems, PCI_COMMAND may randomly flip to 0 on system resume.
> This is devastating to drivers that use pci_set_master(), like NVMe and
> xHCI, to enable DMA in their resume routine, as pci_set_master() can
> inadvertently disable PCI_COMMAND_IO and PCI_COMMAND_MEMORY, making
> resources inaccessible.
>
> The issue is reproducible on all kernel releases, but the situation is
> exacerbated by commit 6cecf02e77ab ("Revert "e1000e: disable s0ix entry
> and exit flows for ME systems"").
>
> Seems like ME can do many things to other PCI devices until it's finally out of
> ULP polling. So ensure e1000e PM ops are serialized by enforcing suspend/resume
> order to workaround the issue.
>
> Of course this will make system suspend and resume a bit slower, but we
> probably need to settle on this workaround until ME is fully supported.
>
> Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=212039
> Signed-off-by: Kai-Heng Feng <kai.heng.feng@canonical.com>

Series "e1000e: Add handshake with the CSME to support s0ix" doesn't
fix the issue, so this patch is still needed.

Kai-Heng

> ---
>  drivers/net/ethernet/intel/e1000e/netdev.c | 14 +++++++++++++-
>  1 file changed, 13 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/net/ethernet/intel/e1000e/netdev.c b/drivers/net/ethernet/intel/e1000e/netdev.c
> index e63445a8ce12..0244d3dd90a3 100644
> --- a/drivers/net/ethernet/intel/e1000e/netdev.c
> +++ b/drivers/net/ethernet/intel/e1000e/netdev.c
> @@ -7319,7 +7319,8 @@ static const struct net_device_ops e1000e_netdev_ops = {
>
>  static void e1000e_create_device_links(struct pci_dev *pdev)
>  {
> -       struct pci_dev *tgp_mei_me;
> +       struct pci_bus *bus = pdev->bus;
> +       struct pci_dev *tgp_mei_me, *p;
>
>         /* Find TGP mei_me devices and make e1000e power depend on mei_me */
>         tgp_mei_me = pci_get_device(PCI_VENDOR_ID_INTEL, 0xa0e0, NULL);
> @@ -7335,6 +7336,17 @@ static void e1000e_create_device_links(struct pci_dev *pdev)
>                 pci_info(pdev, "System and runtime PM depends on %s\n",
>                          pci_name(tgp_mei_me));
>
> +       /* Find other devices in the SoC and make them depend on e1000e */
> +       list_for_each_entry(p, &bus->devices, bus_list) {
> +               if (&p->dev == &pdev->dev || &p->dev == &tgp_mei_me->dev)
> +                       continue;
> +
> +               if (device_link_add(&p->dev, &pdev->dev,
> +                                   DL_FLAG_AUTOREMOVE_SUPPLIER))
> +                       pci_info(p, "System PM depends on %s\n",
> +                                pci_name(pdev));
> +       }
> +
>         pci_dev_put(tgp_mei_me);
>  }
>
> --
> 2.31.1
>