drm: rcar-du: Skip LVDS1 output on Gen3 when using dual-link LVDS mode

In dual-link LVDS mode, the LVDS1 encoder is used as a companion for
LVDS0, and both encoders transmit data from DU0. The LVDS1 output of DU1
can't be used in that case, don't create an encoder and connector for
it.
Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Reviewed-by: Jacopo Mondi <jacopo+renesas@jmondi.org>
Tested-by: Jacopo Mondi <jacopo+renesas@jmondi.org>
Acked-by: Sam Ravnborg <sam@ravnborg.org>
Reviewed-by: Kieran Bingham <kieran.bingham+renesas@ideasonboard.com>

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

@@ -16,6 +16,7 @@
 #include "rcar_du_drv.h"
 #include "rcar_du_encoder.h"
 #include "rcar_du_kms.h"
+#include "rcar_lvds.h"
 
 /* -----------------------------------------------------------------------------
  * Encoder
@@ -97,6 +98,17 @@ int rcar_du_encoder_init(struct rcar_du_device *rcdu,
 		}
 	}
 
+	/*
+	 * On Gen3 skip the LVDS1 output if the LVDS1 encoder is used as a
+	 * companion for LVDS0 in dual-link mode.
+	 */
+	if (rcdu->info->gen >= 3 && output == RCAR_DU_OUTPUT_LVDS1) {
+		if (rcar_lvds_dual_link(bridge)) {
+			ret = -ENOLINK;
+			goto done;
+		}
+	}
+
 	ret = drm_encoder_init(rcdu->ddev, encoder, &encoder_funcs,
 			       DRM_MODE_ENCODER_NONE, NULL);
 	if (ret < 0)

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

@@ -378,7 +378,7 @@ static int rcar_du_encoders_init_one(struct rcar_du_device *rcdu,
 	}
 
 	ret = rcar_du_encoder_init(rcdu, output, entity);
-	if (ret && ret != -EPROBE_DEFER)
+	if (ret && ret != -EPROBE_DEFER && ret != -ENOLINK)
 		dev_warn(rcdu->dev,
 			 "failed to initialize encoder %pOF on output %u (%d), skipping\n",
 			 entity, output, ret);