PM / tick: Add tracepoints for suspend-to-idle diagnostics

Add suspend/resume tracepoints to tick_freeze() and tick_unfreeze()
to catch when timekeeping is suspended and resumed during suspend-to-idle
so as to be able to check whether or not we enter the "frozen" state
and to measure the time spent in it.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: Thomas Gleixner <tglx@linutronix.de>

kernel/time/tick-common.c

@@ -19,6 +19,7 @@
 #include <linux/profile.h>
 #include <linux/sched.h>
 #include <linux/module.h>
+#include <trace/events/power.h>
 
 #include <asm/irq_regs.h>
 
@@ -457,10 +458,13 @@ void tick_freeze(void)
 	raw_spin_lock(&tick_freeze_lock);
 
 	tick_freeze_depth++;
-	if (tick_freeze_depth == num_online_cpus())
+	if (tick_freeze_depth == num_online_cpus()) {
+		trace_suspend_resume(TPS("timekeeping_freeze"),
+				     smp_processor_id(), true);
 		timekeeping_suspend();
-	else
+	} else {
 		tick_suspend_local();
+	}
 
 	raw_spin_unlock(&tick_freeze_lock);
 }
@@ -478,10 +482,13 @@ void tick_unfreeze(void)
 {
 	raw_spin_lock(&tick_freeze_lock);
 
-	if (tick_freeze_depth == num_online_cpus())
+	if (tick_freeze_depth == num_online_cpus()) {
 		timekeeping_resume();
-	else
+		trace_suspend_resume(TPS("timekeeping_freeze"),
+				     smp_processor_id(), false);
+	} else {
 		tick_resume_local();
+	}
 
 	tick_freeze_depth--;