We only have sufficient information for accurate (sub-frame) timestamping
when the modesetting is under our control.
Reported-by: Chris Clayton <chris2553@googlemail.com> Tested-by: Chris Clayton <chris2553@googlemail.com> Reviewed-by: Mario Kleiner <mario.kleiner@tuebingen.mpg.de> Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>