Re: [PATCH v4 2/2] PCI: Don't assume root ports from > 2015 are power manageable

[Rafael J. Wysocki]

On Wed, May 24, 2023 at 9:07 PM Mario Limonciello
<mario.limonciello@xxxxxxx> wrote:
>
> Using a USB keyboard or mouse to wakeup the system from s2idle fails when
> that XHCI device is connected to a USB-C port for an AMD USB4 router.
>
> Due to commit 9d26d3a8f1b0 ("PCI: Put PCIe ports into D3 during suspend")
> all PCIe ports go into D3 during s2idle.
>
> When specific root ports are put into D3 over s2idle on some AMD platforms
> it is not possible for the platform to properly identify wakeup sources.
> This happens whether the root port goes into D3hot or D3cold.
>
> Comparing registers between Linux and Windows 11 this behavior to put
> these specific root ports into D3 at suspend is unique to Linux. On an
> affected system Windows does not put those specific root ports into D3
> over Modern Standby.
>
> Windows doesn't put the root ports into D3 because root ports are not
> power manageable.
>
> Linux shouldn't assume root ports support D3 just because they're on a
> machine newer than 2015, the ports should also be deemed power manageable.
> Add an extra check explicitly for root ports to ensure D3 isn't selected
> for these ports.

"D3 isn't selected for them if they are not power-manageable through
platform firmware."  Or similar.

With this addressed:

Acked-by: Rafael J. Wysocki <rafael@xxxxxxxxxx>

>
> Fixes: 9d26d3a8f1b0 ("PCI: Put PCIe ports into D3 during suspend")
> Reported-by: Iain Lane <iain@xxxxxxxxxxxxxxxxxxx>
> Closes: https://forums.lenovo.com/t5/Ubuntu/Z13-can-t-resume-from-suspend-with-external-USB-keyboard/m-p/5217121
> Signed-off-by: Mario Limonciello <mario.limonciello@xxxxxxx>
> ---
> v3->v4:
>  * Move after refactor
> ---
>  drivers/pci/pci.c | 8 ++++++++
>  1 file changed, 8 insertions(+)
>
> diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
> index d1fa040bcea7..d293db963327 100644
> --- a/drivers/pci/pci.c
> +++ b/drivers/pci/pci.c
> @@ -3015,6 +3015,14 @@ bool pci_bridge_d3_possible(struct pci_dev *bridge)
>         if (dmi_check_system(bridge_d3_blacklist))
>                 return false;
>
> +       /*
> +        * It's not safe to put root ports that don't support power
> +        * management into D3.
> +        */
> +       if (pci_pcie_type(bridge) == PCI_EXP_TYPE_ROOT_PORT &&
> +           !platform_pci_power_manageable(bridge))
> +               return false;
> +
>         /*
>          * It should be safe to put PCIe ports from 2015 or newer
>          * to D3.
> --
> 2.34.1
>