drm/mediatek: Ensure the cursor plane is on top of other overlays

Currently the cursor is placed on the first overlay plane, which means
it will be at the bottom of the stack when the hw does the compositing
with anything other than primary plane. Since mtk doesn't support plane
zpos, change the cursor location to the top-most plane.
Signed-off-by: Sean Paul <seanpaul@chromium.org>
Signed-off-by: CK Hu <ck.hu@mediatek.com>

drivers/gpu/drm/mediatek/mtk_drm_crtc.c

@@ -697,11 +697,12 @@ static int mtk_drm_crtc_num_comp_planes(struct mtk_drm_crtc *mtk_crtc,
 }
 
 static inline
-enum drm_plane_type mtk_drm_crtc_plane_type(unsigned int plane_idx)
+enum drm_plane_type mtk_drm_crtc_plane_type(unsigned int plane_idx,
+					    unsigned int num_planes)
 {
 	if (plane_idx == 0)
 		return DRM_PLANE_TYPE_PRIMARY;
-	else if (plane_idx == 1)
+	else if (plane_idx == (num_planes - 1))
 		return DRM_PLANE_TYPE_CURSOR;
 	else
 		return DRM_PLANE_TYPE_OVERLAY;
@@ -720,7 +721,8 @@ static int mtk_drm_crtc_init_comp_planes(struct drm_device *drm_dev,
 		ret = mtk_plane_init(drm_dev,
 				&mtk_crtc->planes[mtk_crtc->layer_nr],
 				BIT(pipe),
-				mtk_drm_crtc_plane_type(mtk_crtc->layer_nr),
+				mtk_drm_crtc_plane_type(mtk_crtc->layer_nr,
+							num_planes),
 				mtk_ddp_comp_supported_rotations(comp));
 		if (ret)
 			return ret;