[PATCH v5 1/2] drm: renesas: rz-du: rzg2l_du_encoder: convert to of_drm_find_and_get_bridge()

[Luca Ceresoli <luca.ceresoli@bootlin.com>]

of_drm_find_bridge() is deprecated. Move to its replacement
of_drm_find_and_get_bridge() which gets a bridge reference, and ensure it
is put when done.

This is made somewhat simpler by the fact that 'bridge' is a local
variable.

However we need to handle both branches of the main if().

In the 'else' case, just switch to of_drm_find_and_get_bridge() to ensure
the bridge is not freed while in use in the function tail
(drm_bridge_attach() mainly).

In the 'then' case, devm_drm_panel_bridge_add_typed() already increments
the refcount using devres which ties the bridge allocation lifetime to the
device lifetime, so we would not need to do anything. However to have the
same behaviour in both branches take an additional reference here, so that
the bridge needs to be put whichever branch is taken without more
complicated logic.

Reviewed-by: Biju Das <biju.das.jz@bp.renesas.com>
Tested-by: Biju Das <biju.das.jz@bp.renesas.com>
Reviewed-by: Linus Walleij <linusw@kernel.org>
Reviewed-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Reviewed-by: Louis Chauvet <louis.chauvet@bootlin.com>
Signed-off-by: Luca Ceresoli <luca.ceresoli@bootlin.com>
---

Changes in v5:
- simplify error bailout using no_free_ptr

Changes in v4:
- Added comment to clarify the additional drm_bridge_get() in the
  panel_bridge case (keeping the R-by and T-by tags as it's just a comment)
---
 drivers/gpu/drm/renesas/rz-du/rzg2l_du_encoder.c | 13 ++++++++++---
 1 file changed, 10 insertions(+), 3 deletions(-)

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 5e6dd16705e6..d53068733c66 100644
--- a/drivers/gpu/drm/renesas/rz-du/rzg2l_du_encoder.c
+++ b/drivers/gpu/drm/renesas/rz-du/rzg2l_du_encoder.c
@@ -67,7 +67,7 @@ int rzg2l_du_encoder_init(struct rzg2l_du_device  *rcdu,
 {
 	struct rzg2l_du_encoder *renc;
 	struct drm_connector *connector;
-	struct drm_bridge *bridge;
+	struct drm_bridge *bridge __free(drm_bridge_put) = NULL;
 	int ret;
 
 	/*
@@ -84,9 +84,16 @@ int rzg2l_du_encoder_init(struct rzg2l_du_device  *rcdu,
 		bridge = devm_drm_panel_bridge_add_typed(rcdu->dev, panel,
 							 DRM_MODE_CONNECTOR_DPI);
 		if (IS_ERR(bridge))
-			return PTR_ERR(bridge);
+			return PTR_ERR(no_free_ptr(bridge));
+
+		/*
+		 * The reference taken by devm_drm_panel_bridge_add_typed() is
+		 * released automatically. Take a second one for the __free()
+		 * when this function will return.
+		 */
+		drm_bridge_get(bridge);
 	} else {
-		bridge = of_drm_find_bridge(enc_node);
+		bridge = of_drm_find_and_get_bridge(enc_node);
 		if (!bridge)
 			return -EPROBE_DEFER;
 	}

-- 
2.53.0