Re: [PATCH v2 2/6] PCI/PM: Disable device wakeups when halting or powering off system

[Rafael J. Wysocki]

On Mon, Apr 27, 2026 at 10:50 PM Mario Limonciello (AMD)
<superm1@xxxxxxxxxx> wrote:
>
> PCI devices can be configured as wakeup sources from low power states.
> However, when the system is powering off such wakeups are not expected
> and may lead to spurious behavior.
>
> ACPI r6.5, section 16.1.5 notes:
>
>     "Hardware does allow a transition to S0 due to power button press
>      or a Remote Start."
>
> This implies that wakeups from PCI devices should not be relied upon
> in these states.

Does it?  And what about the Remote Start part?  Wake-on-LAN etc?

> To align with this expectation and avoid unintended
> wakeups, disable device wakeup capability during these transitions.
>
> Tested-by: Eric Naim <dnaim@xxxxxxxxxxx>
> Signed-off-by: Mario Limonciello (AMD) <superm1@xxxxxxxxxx>
> ---
>  drivers/pci/pci-driver.c | 3 +++
>  1 file changed, 3 insertions(+)
>
> diff --git a/drivers/pci/pci-driver.c b/drivers/pci/pci-driver.c
> index 2bfefd8db5260..a43ee7bbfb3f5 100644
> --- a/drivers/pci/pci-driver.c
> +++ b/drivers/pci/pci-driver.c
> @@ -1166,6 +1166,9 @@ static int pci_pm_poweroff(struct device *dev)
>         struct pci_dev *pci_dev = to_pci_dev(dev);
>         const struct dev_pm_ops *pm = dev->driver ? dev->driver->pm : NULL;
>
> +       if (device_may_wakeup(dev) && system_state == SYSTEM_POWER_OFF)
> +               device_set_wakeup_enable(dev, false);

1. device_wakeup_disable() can be used here.

2. Do you really want to unregister the wakeup source class device here?

If you need to roll back the poweroff transition, user space will see
this change.

3. What if the device is a NIC that needs to be set up for WoL?

> +
>         if (pci_has_legacy_pm_support(pci_dev))
>                 return pci_legacy_suspend(dev, PMSG_HIBERNATE);
>
> --