[PATCH v9 08/10] drm: renesas: rz-du: Share the encoder of an output driven by several DUs

[Tommaso Merciai]

On a SoC with several DU instances an output can be reachable from more
than one of them, but a drm_bridge can only be attached to one encoder.

In preparation for supporting RZ/G3E, where the DSI and the LVDS channel
1 are reachable from both instances, let the first instance create the
encoder and the others add their CRTC to its possible_crtcs mask, which
rzg2l_du_modeset_init_finish() then extends rather than overwrites.

Without this the second drm_bridge_attach() fails with -EBUSY, leaving
behind the encoder allocated just before it.

SoCs with a single instance are unaffected, as no encoder is ever
already attached.

Signed-off-by: Tommaso Merciai <tommaso.merciai.xr@xxxxxxxxxxxxxx>
---
v8->v9:
 - New patch

 drivers/gpu/drm/renesas/rz-du/rzg2l_du_encoder.c | 12 ++++++++++++
 drivers/gpu/drm/renesas/rz-du/rzg2l_du_kms.c     |  2 +-
 2 files changed, 13 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/renesas/rz-du/rzg2l_du_encoder.c b/drivers/gpu/drm/renesas/rz-du/rzg2l_du_encoder.c
index 5c21c5f9fbaf..45f980ea3c20 100644
--- a/drivers/gpu/drm/renesas/rz-du/rzg2l_du_encoder.c
+++ b/drivers/gpu/drm/renesas/rz-du/rzg2l_du_encoder.c
@@ -129,6 +129,18 @@ int rzg2l_du_encoder_init(struct rzg2l_du_device  *rcdu,
 			return -EPROBE_DEFER;
 	}
 
+	/*
+	 * A bridge can only be attached to one encoder. If another DU instance
+	 * has already attached it, add this instance's CRTC to that encoder.
+	 */
+	if (bridge->dev == rcdu->ddev && bridge->encoder) {
+		const struct rzg2l_du_output_routing *route =
+			&rcdu->info->routes[output];
+
+		bridge->encoder->possible_crtcs |= route->possible_outputs << rcdu->index;
+		return 0;
+	}
+
 	dev_dbg(rcdu->dev, "initializing encoder %pOF for output %s\n",
 		enc_node, rzg2l_du_output_name(output));
 
diff --git a/drivers/gpu/drm/renesas/rz-du/rzg2l_du_kms.c b/drivers/gpu/drm/renesas/rz-du/rzg2l_du_kms.c
index cad378418b38..c20c0e0188ea 100644
--- a/drivers/gpu/drm/renesas/rz-du/rzg2l_du_kms.c
+++ b/drivers/gpu/drm/renesas/rz-du/rzg2l_du_kms.c
@@ -480,7 +480,7 @@ int rzg2l_du_modeset_init_finish(struct drm_device *dev)
 		const struct rzg2l_du_output_routing *route =
 			&renc->dev->info->routes[renc->output];
 
-		encoder->possible_crtcs = route->possible_outputs << renc->dev->index;
+		encoder->possible_crtcs |= route->possible_outputs << renc->dev->index;
 		encoder->possible_clones = (1 << num_encoders) - 1;
 	}
 
-- 
2.54.0