ACPI: C-States: accounting of sleep states

Track the actual time spent in C-States (C2 upwards, we can't determine this
for C1), not only the number of invocations.  This is especially useful for
dynamic ticks / "tickless systems", but is also of interest on normal systems,
as any interrupt activity leads to C-States being exited, not only the timer
interrupt.

The time is being measured in PM timer ticks, so an increase by one equals 279
nanoseconds.
Signed-off-by: Dominik Brodowski <linux@dominikbrodowski.net>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Len Brown <len.brown@intel.com>

drivers/acpi/processor_idle.c

@@ -322,8 +322,6 @@ static void acpi_processor_idle(void)
 		cx = &pr->power.states[ACPI_STATE_C1];
 #endif
 
-	cx->usage++;
-
 	/*
 	 * Sleep:
 	 * ------
@@ -430,6 +428,9 @@ static void acpi_processor_idle(void)
 		local_irq_enable();
 		return;
 	}
+	cx->usage++;
+	if ((cx->type != ACPI_STATE_C1) && (sleep_ticks > 0))
+		cx->time += sleep_ticks;
 
 	next_state = pr->power.state;
 
@@ -1053,9 +1054,10 @@ static int acpi_processor_power_seq_show(struct seq_file *seq, void *offset)
 		else
 			seq_puts(seq, "demotion[--] ");
 
-		seq_printf(seq, "latency[%03d] usage[%08d]\n",
+		seq_printf(seq, "latency[%03d] usage[%08d] duration[%020llu]\n",
 			   pr->power.states[i].latency,
-			   pr->power.states[i].usage);
+			   pr->power.states[i].usage,
+			   pr->power.states[i].time);
 	}
 
       end:

include/acpi/processor.h

@@ -62,6 +62,7 @@ struct acpi_processor_cx {
 	u32 latency_ticks;
 	u32 power;
 	u32 usage;
+	u64 time;
 	struct acpi_processor_cx_policy promotion;
 	struct acpi_processor_cx_policy demotion;
 };