For self-refresh mode WM calculation's "line time" should use
mode's htotal instead of hdisplay. "surface width" is the hdisplay
for display plane and 64 for cursor plane.
Signed-off-by: NZhao Yakui <yakui.zhao@intel.com>
Signed-off-by: NZhenyu Wang <zhenyuw@linux.intel.com>
Signed-off-by: NEric Anholt <eric@anholt.net>