tests/pm_rc6_residency: Measure the sleep duration

The code is confused about the units of CODE_TIME. The comment
says 50 microsseconds, but the actual code makes it 50
milliseconds. Avoid the whole mess by measuring the sleep
duration ourselves. Since the time measurement is taken around
the whole operation it obviously includes a bit of extra, but
at least it's much less than the fixed 50 ms.

For instance on one VLV board I now get something like this:
- Residency in rc6 or deeper state: 3002 ms (ratio to expected duration: 0.98)
+ Residency in rc6 or deeper state: 3001 ms (sleep duration 3003 ms) (ratio to expected duration: 1.00)
so the reported ratio is now much closer to reality.

Reviewed-by: Imre Deak <imre.deak@intel.com>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>

1 files changed, 25 insertions, 10 deletions

diff --git a/tests/pm_rc6_residency.c b/tests/pm_rc6_residency.c
index a1e281cd..27729694 100644
--- a/tests/pm_rc6_residency.c
+++ b/tests/pm_rc6_residency.c
@@ -32,10 +32,10 @@
 #include <string.h>
 #include <unistd.h>
 #include <errno.h>
+#include <time.h>
 
 
-#define SLEEP_DURATION 3000 // in milliseconds
-#define CODE_TIME 50 // in microseconfs
+#define SLEEP_DURATION 3 /* in seconds */
 
 #define RC6_ENABLED	1
 #define RC6P_ENABLED	2
@@ -46,6 +46,7 @@ struct residencies {
 	int media_rc6;
 	int rc6p;
 	int rc6pp;
+	int duration;
 };
 
 static unsigned int readit(const char *path)
@@ -96,14 +97,15 @@ static int read_rc6_residency(const char *name_of_rc6_residency)
 }
 
 static void residency_accuracy(unsigned int diff,
+			       unsigned int duration,
 			       const char *name_of_rc6_residency)
 {
 	double ratio;
 
-	ratio = (double)diff / (SLEEP_DURATION + CODE_TIME);
+	ratio = (double)diff / duration;
 
-	igt_info("Residency in %s or deeper state: %u ms (ratio to expected duration: %.02f)\n",
-		 name_of_rc6_residency, diff, ratio);
+	igt_info("Residency in %s or deeper state: %u ms (sleep duration %u ms) (ratio to expected duration: %.02f)\n",
+		 name_of_rc6_residency, diff, duration, ratio);
 	igt_assert_f(ratio > 0.9 && ratio <= 1,
 		     "Sysfs RC6 residency counter is inaccurate.\n");
 }
@@ -125,12 +127,22 @@ static void read_residencies(int devid, unsigned int rc6_mask,
 		res->rc6pp = read_rc6_residency("rc6pp");
 }
 
+static unsigned long gettime_ms(void)
+{
+	struct timespec ts;
+
+	clock_gettime(CLOCK_MONOTONIC, &ts);
+
+	return ts.tv_sec * 1000 + ts.tv_nsec / 1000000;
+}
+
 static void measure_residencies(int devid, unsigned int rc6_mask,
 				struct residencies *res)
 {
 	struct residencies start = { };
 	struct residencies end = { };
 	int retry;
+	unsigned long t;
 
 	if (!rc6_mask)
 		return;
@@ -147,9 +159,11 @@ static void measure_residencies(int devid, unsigned int rc6_mask,
 	 * different platforms and so fixing it up would be non-trivial.
 	 */
 	for (retry = 0; retry < 2; retry++) {
+		t = gettime_ms();
 		read_residencies(devid, rc6_mask, &start);
-		sleep(SLEEP_DURATION / 1000);
+		sleep(SLEEP_DURATION);
 		read_residencies(devid, rc6_mask, &end);
+		t = gettime_ms() - t;
 
 		if (end.rc6 >= start.rc6 && end.media_rc6 >= start.media_rc6 &&
 		    end.rc6p >= start.rc6p && end.rc6pp >= start.rc6pp)
@@ -161,6 +175,7 @@ static void measure_residencies(int devid, unsigned int rc6_mask,
 	res->rc6p = end.rc6p - start.rc6p;
 	res->rc6pp = end.rc6pp - start.rc6pp;
 	res->media_rc6 = end.media_rc6 - start.media_rc6;
+	res->duration = t;
 
 	/*
 	 * For the purposes of this test case we want a given residency value
@@ -196,22 +211,22 @@ igt_main
 	igt_subtest("rc6-accuracy") {
 		igt_skip_on(!(rc6_mask & RC6_ENABLED));
 
-		residency_accuracy(res.rc6, "rc6");
+		residency_accuracy(res.rc6, res.duration, "rc6");
 	}
 	igt_subtest("media-rc6-accuracy") {
 		igt_skip_on(!((rc6_mask & RC6_ENABLED) &&
 			      (IS_VALLEYVIEW(devid) || IS_CHERRYVIEW(devid))));
 
-		residency_accuracy(res.media_rc6, "media_rc6");
+		residency_accuracy(res.media_rc6, res.duration, "media_rc6");
 	}
 	igt_subtest("rc6p-accuracy") {
 		igt_skip_on(!(rc6_mask & RC6P_ENABLED));
 
-		residency_accuracy(res.rc6p, "rc6p");
+		residency_accuracy(res.rc6p, res.duration, "rc6p");
 	}
 	igt_subtest("rc6pp-accuracy") {
 		igt_skip_on(!(rc6_mask & RC6PP_ENABLED));
 
-		residency_accuracy(res.rc6pp, "rc6pp");
+		residency_accuracy(res.rc6pp, res.duration, "rc6pp");
 	}
 }