diff --git a/drivers/gpu/drm/drm_blend.c b/drivers/gpu/drm/drm_blend.c
index d02709dd2d4a..121481f6aa71 100644
--- a/drivers/gpu/drm/drm_blend.c
+++ b/drivers/gpu/drm/drm_blend.c
@@ -132,10 +132,10 @@
  *	planes. Without this property the primary plane is always below the cursor
  *	plane, and ordering between all other planes is undefined. The positive
  *	Z axis points towards the user, i.e. planes with lower Z position values
- *	are underneath planes with higher Z position values. Note that the Z
- *	position value can also be immutable, to inform userspace about the
- *	hard-coded stacking of overlay planes, see
- *	drm_plane_create_zpos_immutable_property().
+ *	are underneath planes with higher Z position values. Two planes with the
+ *	same Z position value have undefined ordering. Note that the Z position
+ *	value can also be immutable, to inform userspace about the hard-coded
+ *	stacking of planes, see drm_plane_create_zpos_immutable_property().
  *
  * pixel blend mode:
  *	Pixel blend mode is set up with drm_plane_create_blend_mode_property().
diff --git a/include/drm/drm_plane.h b/include/drm/drm_plane.h
index cd5903ad33f7..328773690851 100644
--- a/include/drm/drm_plane.h
+++ b/include/drm/drm_plane.h
@@ -140,10 +140,11 @@ struct drm_plane_state {
 	 * @zpos:
 	 * Priority of the given plane on crtc (optional).
 	 *
-	 * Note that multiple active planes on the same crtc can have an
-	 * identical zpos value. The rule to solving the conflict is to compare
-	 * the plane object IDs; the plane with a higher ID must be stacked on
-	 * top of a plane with a lower ID.
+	 * User-space may set mutable zpos properties so that multiple active
+	 * planes on the same CRTC have identical zpos values. This is a
+	 * user-space bug, but drivers can solve the conflict by comparing the
+	 * plane object IDs; the plane with a higher ID is stacked on top of a
+	 * plane with a lower ID.
 	 *
 	 * See drm_plane_create_zpos_property() and
 	 * drm_plane_create_zpos_immutable_property() for more details.