tests/flip_test: measure inter-frame ts jitter

Yell if it's wrong.

For some odd reason this blows up on my snb. And always on the same
o->count frame on the 2nd crtc ... And we have to thank the hpd poll
helper for that. Comment explaining this added, also made the error
non-fatal.

diff --git a/tests/flip_test.c b/tests/flip_test.c
index 027ef05..97ec891 100644 (file)
--- a/tests/flip_test.c
+++ b/tests/flip_test.c
@@ -72,7 +72,8 @@ struct test_output {
        unsigned int current_fb_id;
        unsigned int fb_ids[2];
        struct kmstest_fb fb_info[2];
-       struct timeval last_flip;
+       struct timeval last_flip_received;
+       struct timeval last_flip_ts;
 };
 
 static void emit_dummy_load(struct test_output *o)
@@ -157,6 +158,7 @@ static void page_flip_handler(int fd, unsigned int frame, unsigned int sec,
        struct test_output *o = data;
        unsigned int new_fb_id;
        struct timeval now, diff, pageflip_ts;
+       double usec_interflip;
 
        pageflip_ts.tv_sec = sec;
        pageflip_ts.tv_usec = usec;
@@ -171,11 +173,24 @@ static void page_flip_handler(int fd, unsigned int frame, unsigned int sec,
                exit(5);
        }
 
-       if (!timercmp(&o->last_flip, &pageflip_ts, <)) {
+       if (!timercmp(&o->last_flip_received, &pageflip_ts, <)) {
                fprintf(stderr, "pageflip ts before the pageflip was issued!\n");
                exit(6);
        }
 
+       if (o->count > 1 && o->flags == 0) {
+               timersub(&pageflip_ts, &o->last_flip_ts, &diff);
+               usec_interflip = 1.0 / ((double) o->mode.vrefresh) * 1000.0 * 1000.0;
+
+               if (fabs((((double) diff.tv_usec) - usec_interflip) / usec_interflip) > 0.005) {
+                       fprintf(stderr, "inter-flip timestamp jitter: %is, %ius\n",
+                               (int) diff.tv_sec, (int) diff.tv_usec);
+                       /* atm this is way too easy to hit, thanks to the hpd
+                        * poll helper :( hence make it non-fatal for now */
+                       //exit(9);
+               }
+       }
+
        o->count++;
 
        o->current_fb_id = !o->current_fb_id;
@@ -216,7 +231,8 @@ static void page_flip_handler(int fd, unsigned int frame, unsigned int sec,
                }
        }
 
-       o->last_flip = now;
+       o->last_flip_received = now;
+       o->last_flip_ts = pageflip_ts;
 }
 
 static void connector_find_preferred_mode(struct test_output *o, int crtc_id)
@@ -407,7 +423,7 @@ static void flip_mode(struct test_output *o, int crtc, int duration)
        evctx.page_flip_handler = page_flip_handler;
 
        gettimeofday(&end, NULL);
-       gettimeofday(&o->last_flip, NULL);
+       gettimeofday(&o->last_flip_received, NULL);
        end.tv_sec += duration;
 
        while (1) {