ACPI / sleep: pm_power_off needs more sanity checks to be installed

Sleep control and status registers need santity checks as well before
ACPI installs acpi_power_off to pm_power_off hook. The checking code in
acpi_enter_sleep_state() is too late, we should not allow a not-working
pm_power_off function to be hooked up.
Signed-off-by: Aubrey Li <aubrey.li@intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

drivers/acpi/sleep.c

@@ -807,7 +807,12 @@ int __init acpi_sleep_init(void)
 	acpi_sleep_hibernate_setup();
 
 	status = acpi_get_sleep_type_data(ACPI_STATE_S5, &type_a, &type_b);
-	if (ACPI_SUCCESS(status)) {
+	/*
+	 * Check both ACPI S5 object and ACPI sleep registers to
+	 * install pm_power_off_prepare/pm_power_off hook
+	 */
+	if (ACPI_SUCCESS(status) && acpi_gbl_FADT.sleep_control.address
+	    && acpi_gbl_FADT.sleep_status.address) {
 		sleep_states[ACPI_STATE_S5] = 1;
 		pm_power_off_prepare = acpi_power_off_prepare;
 		pm_power_off = acpi_power_off;