On 9/10/25 10:06 AM, Bjorn Helgaas wrote:
On Tue, Sep 09, 2025 at 02:16:12PM -0500, Mario Limonciello (AMD) wrote:
PCI devices can be configured as wakeup sources from low power states.
However, when the system is halting or powering off such wakeups are
not expected and may lead to spurious behavior.
I'm a little unclear on the nomenclature for these low power states,
so I think it would be helpful to connect to the user action, e.g.,
suspend/hibernate/etc, and the ACPI state, e.g.,
... when the system is hibernating (e.g., transitioning to ACPI S4
and halting) or powering off (e.g., transitioning to ACPI S5 soft
off), such wakeups are not expected ...
I will try to firm it up in the commit message. But yes you're getting
the intent, having a wakeup occur at S5 would be unexpected, and would
likely change semantics of what people "think" powering off a machine means.
When I suspend or power off my laptop from the GUI user interface, I
want to know if keyboard or mouse activity will resume or if I need to
press the power button.
The way the kernel is set up today you get a single wakeup sysfs file
for a device and that wakeup file means 3 things:
* abort the process of entering a suspend state or hibernate
* wake up the machine from a suspend state
* wake up the machine from hibernate
ACPI r6.5, section 16.1.5 notes:
"Hardware does allow a transition to S0 due to power button press
or a Remote Start."
Important to note here that sec 16.1.5 is specifically for "S5 Soft
Off State".
S4 is a sleeping state and presumably sec 16.1.6 ("Transitioning from
the Working to the Sleeping State") applies. That section mentions
wakeup devices, so it's not obvious to me that PCI device wakeup
should be disabled for S4.
It actually /shouldn't/ be disabled for S4 - it should only be disabled
for S5.
Are you implying a bug in the flow? I didn't think there was one:
During entering hibernate the poweroff() call will have system_state =
SYSTEM_SUSPEND so wakeups would be enabled.
For powering off the system using hibernate flows poweroff() call would
have system_state = SYSTEM_HALT or SYSTEM_POWER_OFF.
This implies that wakeups from PCI devices should not be relied upon
in these states. To align with this expectation and avoid unintended
wakeups, disable device wakeup capability during these transitions.
Tested-by: Eric Naim <dn...@cachyos.org>
Signed-off-by: Mario Limonciello (AMD) <supe...@kernel.org>
---
v7:
* Reword title
* Reword commit
v5:
* Re-order
* Add tags
v4:
*
https://lore.kernel.org/linux-pci/20250616175019.3471583-1-supe...@kernel.org/
---
drivers/pci/pci-driver.c | 4 ++++
1 file changed, 4 insertions(+)
diff --git a/drivers/pci/pci-driver.c b/drivers/pci/pci-driver.c
index 63665240ae87f..f201d298d7173 100644
--- a/drivers/pci/pci-driver.c
+++ b/drivers/pci/pci-driver.c
@@ -1139,6 +1139,10 @@ 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_HALT || system_state == SYSTEM_POWER_OFF))
+ device_set_wakeup_enable(dev, false);
+
if (pci_has_legacy_pm_support(pci_dev))
return pci_legacy_suspend(dev, PMSG_HIBERNATE);
--
2.43.0
