drm/sun4i: Allow VI layers to be primary planes

D1's mixer 1 has no UI layers, only a single VI layer. That means the
mixer can only be used if the primary plane comes from this VI layer.
Add the code to handle this case.
Signed-off-by: Samuel Holland <samuel@sholland.org>
Reviewed-by: Jernej Skrabec <jernej.skrabec@gmail.com>
Signed-off-by: Maxime Ripard <maxime@cerno.tech>
Link: https://patchwork.freedesktop.org/patch/msgid/20220424162633.12369-10-samuel@sholland.org

drivers/gpu/drm/sun4i/sun8i_vi_layer.c

@@ -542,6 +542,7 @@ struct sun8i_vi_layer *sun8i_vi_layer_init_one(struct drm_device *drm,
 					       struct sun8i_mixer *mixer,
 					       int index)
 {
+	enum drm_plane_type type = DRM_PLANE_TYPE_OVERLAY;
 	u32 supported_encodings, supported_ranges;
 	unsigned int plane_cnt, format_count;
 	struct sun8i_vi_layer *layer;
@@ -560,12 +561,15 @@ struct sun8i_vi_layer *sun8i_vi_layer_init_one(struct drm_device *drm,
 		format_count = ARRAY_SIZE(sun8i_vi_layer_formats);
 	}
 
+	if (!mixer->cfg->ui_num && index == 0)
+		type = DRM_PLANE_TYPE_PRIMARY;
+
 	/* possible crtcs are set later */
 	ret = drm_universal_plane_init(drm, &layer->plane, 0,
 				       &sun8i_vi_layer_funcs,
 				       formats, format_count,
 				       sun8i_layer_modifiers,
-				       DRM_PLANE_TYPE_OVERLAY, NULL);
+				       type, NULL);
 	if (ret) {
 		dev_err(drm->dev, "Couldn't initialize layer\n");
 		return ERR_PTR(ret);