ktime_us_delta
time = ktime_us_delta(now.ktime, prev->ktime);
ktime_us_delta(end_vbl_time, crtc->debug.start_vbl_time),
else if (ktime_us_delta(end_vbl_time, crtc->debug.start_vbl_time) >
ktime_us_delta(end_vbl_time, crtc->debug.start_vbl_time),