linux-kernel - [PATCH 4/6] drm/mcde: dsi: convert to of_drm_find_and_get

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Message-Id: <20260116-drm-bridge-alloc-getput-drm_of_find_bridge-4-v1-4-e34b38f50d27@bootlin.com>
Date: Fri, 16 Jan 2026 18:32:39 +0100
From: Luca Ceresoli <luca.ceresoli@...tlin.com>
To: Biju Das <biju.das.jz@...renesas.com>, 
 Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>, 
 Maxime Ripard <mripard@...nel.org>, Thomas Zimmermann <tzimmermann@...e.de>, 
 David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>, 
 Anitha Chrisanthus <anitha.chrisanthus@...el.com>, 
 Edmund Dea <edmund.j.dea@...el.com>, Linus Walleij <linusw@...nel.org>, 
 Laurent Pinchart <laurent.pinchart+renesas@...asonboard.com>, 
 Tomi Valkeinen <tomi.valkeinen+renesas@...asonboard.com>, 
 Kieran Bingham <kieran.bingham+renesas@...asonboard.com>, 
 Geert Uytterhoeven <geert+renesas@...der.be>, 
 Magnus Damm <magnus.damm@...il.com>, 
 Tomi Valkeinen <tomi.valkeinen@...asonboard.com>
Cc: Hui Pu <Hui.Pu@...ealthcare.com>, Ian Ray <ian.ray@...ealthcare.com>, 
 Thomas Petazzoni <thomas.petazzoni@...tlin.com>, 
 dri-devel@...ts.freedesktop.org, linux-renesas-soc@...r.kernel.org, 
 linux-kernel@...r.kernel.org, Luca Ceresoli <luca.ceresoli@...tlin.com>
Subject: [PATCH 4/6] drm/mcde: dsi: convert to of_drm_find_and_get_bridge()

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.

We need to handle the two cases: when a panel is found and when it isn't,
even though the latter is not supported. So:

 * in case a panel is not found and bridge is, get a reference to the
   found bridge
 * in case a panel is found, get a reference to the panel_bridge when it
   is added, so the following code always get exactly one reference that
   it needs to put

Finally, use the next_bridge pointer in struct drm_bridge in order to
simplify putting the reference.

Signed-off-by: Luca Ceresoli <luca.ceresoli@...tlin.com>
---
 drivers/gpu/drm/mcde/mcde_dsi.c | 13 +++++++------
 1 file changed, 7 insertions(+), 6 deletions(-)

diff --git a/drivers/gpu/drm/mcde/mcde_dsi.c b/drivers/gpu/drm/mcde/mcde_dsi.c
index 3faebe571fc2..bd2135fd4293 100644
--- a/drivers/gpu/drm/mcde/mcde_dsi.c
+++ b/drivers/gpu/drm/mcde/mcde_dsi.c
@@ -40,7 +40,6 @@ struct mcde_dsi {
 	struct mcde *mcde;
 	struct drm_bridge bridge;
 	struct drm_panel *panel;
-	struct drm_bridge *bridge_out;
 	struct mipi_dsi_host dsi_host;
 	struct mipi_dsi_device *mdsi;
 	const struct drm_display_mode *mode;
@@ -1060,7 +1059,7 @@ static int mcde_dsi_bridge_attach(struct drm_bridge *bridge,
 	}
 
 	/* Attach the DSI bridge to the output (panel etc) bridge */
-	return drm_bridge_attach(encoder, d->bridge_out, bridge, flags);
+	return drm_bridge_attach(encoder, d->bridge.next_bridge, bridge, flags);
 }
 
 static const struct drm_bridge_funcs mcde_dsi_bridge_funcs = {
@@ -1076,7 +1075,7 @@ static int mcde_dsi_bind(struct device *dev, struct device *master,
 	struct mcde_dsi *d = dev_get_drvdata(dev);
 	struct device_node *child;
 	struct drm_panel *panel = NULL;
-	struct drm_bridge *bridge = NULL;
+	struct drm_bridge *bridge __free(drm_bridge_put) = NULL;
 
 	if (!of_get_available_child_count(dev->of_node)) {
 		dev_info(dev, "unused DSI interface\n");
@@ -1112,7 +1111,8 @@ static int mcde_dsi_bind(struct device *dev, struct device *master,
 				PTR_ERR(panel));
 			panel = NULL;
 
-			bridge = of_drm_find_bridge(child);
+			drm_bridge_put(bridge); // In case of multiple matching loops
+			bridge = of_drm_find_and_get_bridge(child);
 			if (!bridge) {
 				dev_err(dev, "failed to find bridge\n");
 				of_node_put(child);
@@ -1127,6 +1127,7 @@ static int mcde_dsi_bind(struct device *dev, struct device *master,
 			dev_err(dev, "error adding panel bridge\n");
 			return PTR_ERR(bridge);
 		}
+		drm_bridge_get(bridge);
 		dev_info(dev, "connected to panel\n");
 		d->panel = panel;
 	} else if (bridge) {
@@ -1138,7 +1139,7 @@ static int mcde_dsi_bind(struct device *dev, struct device *master,
 		return -ENODEV;
 	}
 
-	d->bridge_out = bridge;
+	d->bridge.next_bridge = drm_bridge_get(bridge);
 
 	/* Create a bridge for this DSI channel */
 	d->bridge.of_node = dev->of_node;
@@ -1158,7 +1159,7 @@ static void mcde_dsi_unbind(struct device *dev, struct device *master,
 	struct mcde_dsi *d = dev_get_drvdata(dev);
 
 	if (d->panel)
-		drm_panel_bridge_remove(d->bridge_out);
+		drm_panel_bridge_remove(d->bridge.next_bridge);
 	regmap_update_bits(d->prcmu, PRCM_DSI_SW_RESET,
 			   PRCM_DSI_SW_RESET_DSI0_SW_RESETN, 0);
 }

-- 
2.52.0