drm: rcar-du: lvds: Get dual link configuration from DT

For dual-LVDS configurations, it is now possible to mark the
DT port nodes for the sink with boolean properties (like
dual-lvds-even-pixels and dual-lvds-odd-pixels) to let drivers
know the encoders need to be configured in dual-LVDS mode.

Rework the implementation of rcar_lvds_parse_dt_companion
to make use of the DT markers while keeping backward
compatibility.

Signed-off-by: Fabrizio Castro <fabrizio.castro@bp.renesas.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>

drivers/gpu/drm/rcar-du/rcar_lvds.c

@@ -678,7 +678,10 @@ static int rcar_lvds_parse_dt_companion(struct rcar_lvds *lvds)
 {
 	const struct of_device_id *match;
 	struct device_node *companion;
+	struct device_node *port0, *port1;
+	struct rcar_lvds *companion_lvds;
 	struct device *dev = lvds->dev;
+	int dual_link;
 	int ret = 0;
 
 	/* Locate the companion LVDS encoder for dual-link operation, if any. */
@@ -697,13 +700,54 @@ static int rcar_lvds_parse_dt_companion(struct rcar_lvds *lvds)
 		goto done;
 	}
 
+	/*
+	 * We need to work out if the sink is expecting us to function in
+	 * dual-link mode. We do this by looking at the DT port nodes we are
+	 * connected to, if they are marked as expecting even pixels and
+	 * odd pixels than we need to enable vertical stripe output.
+	 */
+	port0 = of_graph_get_port_by_id(dev->of_node, 1);
+	port1 = of_graph_get_port_by_id(companion, 1);
+	dual_link = drm_of_lvds_get_dual_link_pixel_order(port0, port1);
+	of_node_put(port0);
+	of_node_put(port1);
+
+	if (dual_link >= DRM_LVDS_DUAL_LINK_EVEN_ODD_PIXELS)
+		lvds->dual_link = true;
+	else if (lvds->next_bridge && lvds->next_bridge->timings)
+		/*
+		 * Early dual-link bridge specific implementations populate the
+		 * timings field of drm_bridge, read the dual_link flag off the
+		 * bridge directly for backward compatibility.
+		 */
+		lvds->dual_link = lvds->next_bridge->timings->dual_link;
+
+	if (!lvds->dual_link) {
+		dev_dbg(dev, "Single-link configuration detected\n");
+		goto done;
+	}
+
 	lvds->companion = of_drm_find_bridge(companion);
 	if (!lvds->companion) {
 		ret = -EPROBE_DEFER;
 		goto done;
 	}
 
-	dev_dbg(dev, "Found companion encoder %pOF\n", companion);
+	dev_dbg(dev,
+		"Dual-link configuration detected (companion encoder %pOF)\n",
+		companion);
+
+	/*
+	 * FIXME: We should not be messing with the companion encoder private
+	 * data from the primary encoder, we should rather let the companion
+	 * encoder work things out on its own. However, the companion encoder
+	 * doesn't hold a reference to the primary encoder, and
+	 * drm_of_lvds_get_dual_link_pixel_order needs to be given references
+	 * to the output ports of both encoders, therefore leave it like this
+	 * for the time being.
+	 */
+	companion_lvds = bridge_to_rcar_lvds(lvds->companion);
+	companion_lvds->dual_link = true;
 
 done:
 	of_node_put(companion);
@@ -720,13 +764,7 @@ static int rcar_lvds_parse_dt(struct rcar_lvds *lvds)
 	if (ret)
 		goto done;
 
-	if ((lvds->info->quirks & RCAR_LVDS_QUIRK_DUAL_LINK) &&
-	    lvds->next_bridge)
-		lvds->dual_link = lvds->next_bridge->timings
-				? lvds->next_bridge->timings->dual_link
-				: false;
-
-	if (lvds->dual_link)
+	if (lvds->info->quirks & RCAR_LVDS_QUIRK_DUAL_LINK)
 		ret = rcar_lvds_parse_dt_companion(lvds);
 
 done: