[igt-dev] [PATCH i-g-t v3] igt: tests: kms_vblank: Stop using magic value

[Stanislav Lisovskiy]

Lot of tests fail, when assertion checking
how many vblanks should have passed during
suspend/resume is compared to magic value 150.

At the same time even for failed cases, sometimes
it is clearly visible that there were no issue -
simply suspend took longer on that machine.
If suspend took around 10 s and we get roughly
60 vblanks per second the value then should be
around 600 and not 150.

This change removes 150 magic value and starts
to use calculation of what it is expected to
be instead of being hardcoded.

v2: Add possible error delta interval, where expected
    vblanks must lie, i.e:
     [estimated_vblanks - err, estimated_vblanks + err]

v3: Made an error range for estimated vblanks a bit less
    strict.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=104894
Signed-off-by: Stanislav Lisovskiy <stanislav.lisovskiy at intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala at linux.intel.com>
---
 tests/kms_vblank.c | 17 +++++++++++++++--
 1 file changed, 15 insertions(+), 2 deletions(-)

diff --git a/tests/kms_vblank.c b/tests/kms_vblank.c
index dafadb58..79ff97b2 100644
--- a/tests/kms_vblank.c
+++ b/tests/kms_vblank.c
@@ -332,14 +332,21 @@ static int get_vblank(int fd, enum pipe pipe, unsigned flags)
 	return vbl.reply.sequence;
 }
 
+#define VBLANK_ERR 5
+
 static void vblank_ts_cont(data_t *data, int fd, int nchildren)
 {
 	igt_display_t *display = &data->display;
 	igt_output_t *output = data->output;
 	int seq1, seq2;
 	union drm_wait_vblank vbl;
+	struct timespec start, end;
+	int estimated_vblanks = 0;
+	int vrefresh = igt_output_get_mode(output)->vrefresh;
+	double time_elapsed;
 
 	seq1 = get_vblank(fd, data->pipe, 0);
+	clock_gettime(CLOCK_MONOTONIC, &start);
 
 	if (data->flags & DPMS) {
 		igt_output_set_prop_value(output, IGT_CONNECTOR_DPMS, DRM_MODE_DPMS_OFF);
@@ -377,11 +384,17 @@ static void vblank_ts_cont(data_t *data, int fd, int nchildren)
 	}
 
 	seq2 = get_vblank(fd, data->pipe, 0);
+	clock_gettime(CLOCK_MONOTONIC, &end);
+
+	time_elapsed = igt_time_elapsed(&start, &end);
+	estimated_vblanks = (int)(time_elapsed * vrefresh);
 
 	igt_debug("testing ts continuity: Current frame %u, old frame %u\n", seq2, seq1);
 
-	igt_assert_f(seq2 - seq1 >= 0, "unexpected vblank seq %u, should be >= %u\n", seq2, seq1);
-	igt_assert_f(seq2 - seq1 <= 150, "unexpected vblank seq %u, should be < %u\n", seq2, seq1 + 150);
+	igt_assert_f(seq2 - seq1 >= 0, "elapsed %f(%d vblanks) unexpected vblank seq %u, should be > %u\n", time_elapsed,
+			estimated_vblanks, seq2, seq1);
+	igt_assert_f(seq2 - seq1 <= estimated_vblanks + VBLANK_ERR, "elapsed %f(%d vblanks) unexpected vblank seq %u, should be <= %u\n", time_elapsed,
+			estimated_vblanks, seq2, seq1 + estimated_vblanks);
 }
 
 static void run_subtests_for_pipe(data_t *data)
-- 
2.17.1