ACPI: PM: Fix regression in acpi_device_set_power()

Commit f850a48a0799 ("ACPI: PM: Allow transitions to D0 to occur in
special cases") overlooked the fact that acpi_power_transition() may
change the power.state value for the target device and if that
happens, it may confuse acpi_device_set_power() and cause it to
omit the _PS0 evaluation which on some systems is necessary to
change power states of devices from low-power to D0.

Fix that by saving the current value of power.state for the
target device before passing it to acpi_power_transition() and
using the saved value in a subsequent check.

Fixes: f850a48a0799 ("ACPI: PM: Allow transitions to D0 to occur in special cases")
Reported-by: Kai-Heng Feng <kai.heng.feng@canonical.com>
Reported-by: Mario Limonciello <mario.limonciello@dell.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Tested-by: Kai-Heng Feng <kai.heng.feng@canonical.com>
Tested-by: Mario Limonciello <mario.limonciello@dell.com>

diff --git a/drivers/acpi/device_pm.c b/drivers/acpi/device_pm.c
index 28cffaa..f616b16 100644 (file)
--- a/drivers/acpi/device_pm.c
+++ b/drivers/acpi/device_pm.c
@@ -232,13 +232,15 @@ int acpi_device_set_power(struct acpi_device *device, int state)
                if (device->power.flags.power_resources)
                        result = acpi_power_transition(device, target_state);
        } else {
+               int cur_state = device->power.state;
+
                if (device->power.flags.power_resources) {
                        result = acpi_power_transition(device, ACPI_STATE_D0);
                        if (result)
                                goto end;
                }
 
-               if (device->power.state == ACPI_STATE_D0) {
+               if (cur_state == ACPI_STATE_D0) {
                        int psc;
 
                        /* Nothing to do here if _PSC is not present. */