[Intel-gfx] [PATCH i-g-t v2] lib/igt_core: Prefer CLOCK_MONOTONIC_RAW

[Joonas Lahtinen]

CLOCK_MONOTONIC_RAW is not affected by NTP, so it should be THE clock
used for timing execution of tests.

v2:
- Cache the used clock (Chris)
- Do not change the clock during execution
- Spit out and error if monotonic time can not be read

Cc: Thomas Wood <thomas.wood at intel.com>
Cc: Chris Wilson <chris at chris-wilson.co.uk>
Signed-off-by: Joonas Lahtinen <joonas.lahtinen at linux.intel.com>
---
 lib/igt_core.c | 20 ++++++++++++++++++--
 1 file changed, 18 insertions(+), 2 deletions(-)

diff --git a/lib/igt_core.c b/lib/igt_core.c
index 04a0ab2..c56bc15 100644
--- a/lib/igt_core.c
+++ b/lib/igt_core.c
@@ -220,6 +220,7 @@ static char *run_single_subtest = NULL;
 static bool run_single_subtest_found = false;
 static const char *in_subtest = NULL;
 static struct timespec subtest_time;
+static clockid_t igt_clock = (clockid_t)-1;
 static bool in_fixture = false;
 static bool test_with_subtests = false;
 static bool in_atexit_handler = false;
@@ -341,10 +342,25 @@ static void gettime(struct timespec *ts)
 {
 	memset(ts, 0, sizeof(*ts));
 
+	// Stay on the same clock for consistency.
+	if (igt_clock != (clockid_t)-1) {
+		clock_gettime(igt_clock, ts);
+		return;
+	}
+
+#ifdef CLOCK_MONOTONIC_RAW
+	if (!clock_gettime(igt_clock = CLOCK_MONOTONIC_RAW, ts))
+		return;
+#endif
 #ifdef CLOCK_MONOTONIC_COARSE
-	if (clock_gettime(CLOCK_MONOTONIC_COARSE, ts))
+	if (!clock_gettime(igt_clock = CLOCK_MONOTONIC_COARSE, ts))
+		return;
 #endif
-		clock_gettime(CLOCK_MONOTONIC, ts);
+	if (!clock_gettime(igt_clock = CLOCK_MONOTONIC, ts))
+		return;
+
+	igt_warn("Unable to get monotonic time!\n");
+	exit(IGT_EXIT_FAILURE);
 }
 
 bool __igt_fixture(void)
-- 
2.4.3