ACPI / PM: Check low power idle constraints for debug only

For SoC to achieve its lowest power platform idle state a set of hardware
preconditions must be met. These preconditions or constraints can be
obtained by issuing a device specific method (_DSM) with function "1".
Refer to the document provided in the link below.

Here during initialization (from attach() callback of LPS0 device), invoke
function 1 to get the device constraints. Each enabled constraint is
stored in a table.

The devices in this table are used to check whether they were in required
minimum state, while entering suspend. This check is done from platform
freeze wake() callback, only when /sys/power/pm_debug_messages attribute
is non zero.

If any constraint is not met and device is ACPI power managed then it
prints the device information to kernel logs.

Also if debug is enabled in acpi/sleep.c, the constraint table and state
of each device on wake is dumped in kernel logs.

Since pm_debug_messages_on setting is used as condition to check
constraints outside kernel/power/main.c, pm_debug_messages_on is changed
to a global variable.

Link: http://www.uefi.org/sites/default/files/resources/Intel_ACPI_Low_Power_S0_Idle.pdf
Signed-off-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

1 files changed, 2 insertions, 0 deletions

diff --git a/include/linux/suspend.h b/include/linux/suspend.h
index 0d41daf7e89d..d10b7980799d 100644
--- a/include/linux/suspend.h
+++ b/include/linux/suspend.h
@@ -495,9 +495,11 @@ static inline void unlock_system_sleep(void) {}
 
 #ifdef CONFIG_PM_SLEEP_DEBUG
 extern bool pm_print_times_enabled;
+extern bool pm_debug_messages_on;
 extern __printf(2, 3) void __pm_pr_dbg(bool defer, const char *fmt, ...);
 #else
 #define pm_print_times_enabled  (false)
+#define pm_debug_messages_on    (false)
 
 #include <linux/printk.h>