CVT_MIN_VSYNC_BP  232 drivers/gpu/drm/drm_modes.c #define CVT_MIN_VSYNC_BP	550
CVT_MIN_VSYNC_BP  428 drivers/media/v4l2-core/v4l2-dv-timings.c #define CVT_MIN_VSYNC_BP	550	/* min time of vsync + back porch (us) */