gen7_enable_fbc() may write to some registers which we've already touched, so use RMW so that we don't undo any previous updates. Also note that we implemnt WaFbcAsynchFlipDisableFbcQueue:bdw. Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com> Reviewed-by: Damien Lespiau <damien.lespiau@intel.com> Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>