When a device’s power_manageable flag is false, we currently only
fall back to the direct parent’s power state. In a deep hierarchy
there may be a more distant ancestor that does support power
management.
Walk up the parent chain until we find the closest power_manageable
ancestor and use its power state. If none is found, default to
ACPI_STATE_D0 (fully on).
Signed-off-by: Guan-Chun.Wu <409411716@xxxxxxxxxxxxxx>
---
drivers/acpi/device_pm.c | 19 +++++++++++++++++--
1 file changed, 17 insertions(+), 2 deletions(-)
diff --git a/drivers/acpi/device_pm.c b/drivers/acpi/device_pm.c
index dbd4446025ec..81b47fb00e80 100644
--- a/drivers/acpi/device_pm.c
+++ b/drivers/acpi/device_pm.c
@@ -84,8 +84,23 @@ int acpi_device_get_power(struct acpi_device *device, int *state)
parent = acpi_dev_parent(device);
if (!device->flags.power_manageable) {
- /* TBD: Non-recursive algorithm for walking up hierarchy. */
- *state = parent ? parent->power.state : ACPI_STATE_D0;
+ /*
+ * If the device itself is not power-manageable,
+ * walk up the parent hierarchy to find the closest
+ * ancestor that is power-manageable.
+ * Use that ancestor's power state as an estimate
+ * for this device. If no such ancestor exists,
+ * default to D0 (Fully On).
+ */
+ struct acpi_device *ancestor = parent;
+ /*
+ * Keep traversing up until a power-manageable ancestor
+ * is found or the root is reached
+ */
+ while (ancestor && !ancestor->flags.power_manageable)
+ ancestor = acpi_dev_parent(ancestor);
+ /* Use the found ancestor's power state, or D0 if none is found */
+ *state = ancestor ? ancestor->power.state : ACPI_STATE_D0;
goto out;
}
--
2.34.1
