drm/atomic: Reject attempts to use multiple rotation angles at once

The rotation property should only accept exactly one rotation angle
at once. Let's reject attempts to set none or multiple angles.

Testcase: igt/kms_rotation_crc/bad-rotation
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/1474907460-10717-3-git-send-email-ville.syrjala@linux.intel.com

drivers/gpu/drm/drm_atomic.c

@@ -706,6 +706,8 @@ int drm_atomic_plane_set_property(struct drm_plane *plane,
 	} else if (property == config->prop_src_h) {
 		state->src_h = val;
 	} else if (property == config->rotation_property) {
+		if (!is_power_of_2(val & DRM_ROTATE_MASK))
+			return -EINVAL;
 		state->rotation = val;
 	} else if (property == plane->zpos_property) {
 		state->zpos = val;