PM/sleep: Expose suspend stats in sysfs

Userspace can get suspend stats from the suspend stats debugfs node.
Since debugfs doesn't have stable ABI, expose suspend stats in
sysfs under /sys/power/suspend_stats.

Signed-off-by: Kalesh Singh <kaleshsingh@google.com>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

Documentation/ABI/testing/sysfs-power

@@ -301,3 +301,109 @@ Description:
 
 		Using this sysfs file will override any values that were
 		set using the kernel command line for disk offset.
+
+What:		/sys/power/suspend_stats
+Date:		July 2019
+Contact:	Kalesh Singh <kaleshsingh96@gmail.com>
+Description:
+		The /sys/power/suspend_stats directory contains suspend related
+		statistics.
+
+What:		/sys/power/suspend_stats/success
+Date:		July 2019
+Contact:	Kalesh Singh <kaleshsingh96@gmail.com>
+Description:
+		The /sys/power/suspend_stats/success file contains the number
+		of times entering system sleep state succeeded.
+
+What:		/sys/power/suspend_stats/fail
+Date:		July 2019
+Contact:	Kalesh Singh <kaleshsingh96@gmail.com>
+Description:
+		The /sys/power/suspend_stats/fail file contains the number
+		of times entering system sleep state failed.
+
+What:		/sys/power/suspend_stats/failed_freeze
+Date:		July 2019
+Contact:	Kalesh Singh <kaleshsingh96@gmail.com>
+Description:
+		The /sys/power/suspend_stats/failed_freeze file contains the
+		number of times freezing processes failed.
+
+What:		/sys/power/suspend_stats/failed_prepare
+Date:		July 2019
+Contact:	Kalesh Singh <kaleshsingh96@gmail.com>
+Description:
+		The /sys/power/suspend_stats/failed_prepare file contains the
+		number of times preparing all non-sysdev devices for
+		a system PM transition failed.
+
+What:		/sys/power/suspend_stats/failed_resume
+Date:		July 2019
+Contact:	Kalesh Singh <kaleshsingh96@gmail.com>
+Description:
+		The /sys/power/suspend_stats/failed_resume file contains the
+		number of times executing "resume" callbacks of
+		non-sysdev devices failed.
+
+What:		/sys/power/suspend_stats/failed_resume_early
+Date:		July 2019
+Contact:	Kalesh Singh <kaleshsingh96@gmail.com>
+Description:
+		The /sys/power/suspend_stats/failed_resume_early file contains
+		the number of times executing "early resume" callbacks
+		of devices failed.
+
+What:		/sys/power/suspend_stats/failed_resume_noirq
+Date:		July 2019
+Contact:	Kalesh Singh <kaleshsingh96@gmail.com>
+Description:
+		The /sys/power/suspend_stats/failed_resume_noirq file contains
+		the number of times executing "noirq resume" callbacks
+		of devices failed.
+
+What:		/sys/power/suspend_stats/failed_suspend
+Date:		July 2019
+Contact:	Kalesh Singh <kaleshsingh96@gmail.com>
+Description:
+		The /sys/power/suspend_stats/failed_suspend file contains
+		the number of times executing "suspend" callbacks
+		of all non-sysdev devices failed.
+
+What:		/sys/power/suspend_stats/failed_suspend_late
+Date:		July 2019
+Contact:	Kalesh Singh <kaleshsingh96@gmail.com>
+Description:
+		The /sys/power/suspend_stats/failed_suspend_late file contains
+		the number of times executing "late suspend" callbacks
+		of all devices failed.
+
+What:		/sys/power/suspend_stats/failed_suspend_noirq
+Date:		July 2019
+Contact:	Kalesh Singh <kaleshsingh96@gmail.com>
+Description:
+		The /sys/power/suspend_stats/failed_suspend_noirq file contains
+		the number of times executing "noirq suspend" callbacks
+		of all devices failed.
+
+What:		/sys/power/suspend_stats/last_failed_dev
+Date:		July 2019
+Contact:	Kalesh Singh <kaleshsingh96@gmail.com>
+Description:
+		The /sys/power/suspend_stats/last_failed_dev file contains
+		the last device for which a suspend/resume callback failed.
+
+What:		/sys/power/suspend_stats/last_failed_errno
+Date:		July 2019
+Contact:	Kalesh Singh <kaleshsingh96@gmail.com>
+Description:
+		The /sys/power/suspend_stats/last_failed_errno file contains
+		the errno of the last failed attempt at entering
+		system sleep state.
+
+What:		/sys/power/suspend_stats/last_failed_step
+Date:		July 2019
+Contact:	Kalesh Singh <kaleshsingh96@gmail.com>
+Description:
+		The /sys/power/suspend_stats/last_failed_step file contains
+		the last failed step in the suspend/resume path.