drm/i915: Avoid underruns when disabling sprites
drm/i915: Avoid underruns when disabling sprites

As the watermark registers aren't double bufferd, clearing the
watermarks immediately after writing the sprite registers can be
hazardous.

Until we have something better, add a wait for vblank between the
two steps to make sure the sprite no longer needs the watermark
levels before we clear them.

Signed-off-by: Ville Syrjälä <cd6e8d405ca90be3a03d5427c5b24fbd2d68dcc4@linux.intel.com>
Reviewed-by: Imre Deak <fbd5edba1988036c8923f0cca0cce6ac4811db29@intel.com>
Signed-off-by: Daniel Vetter <c1b6782c4af8f0673da8923a0702a1832e5940f4@ffwll.ch>

KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs