Re: [PATCH 11/11] drm/bridge: tc358768: Add DRM_BRIDGE_ATTACH_NO_CONNECTOR support

[Tomi Valkeinen]

Hi Sam,

On 14/08/2023 13:10, Sam Ravnborg wrote:
Hi Tomi,
 From c13c691bd8826b978325575be9a87f577b83b86b Mon Sep 17 00:00:00 2001
From: Tomi Valkeinen <tomi.valkei...@ideasonboard.com>
Date: Mon, 14 Aug 2023 13:02:23 +0300
Subject: [PATCH] drm/bridge: tc358768: fix 'Add DRM_BRIDGE_ATTACH_NO_CONNECTOR
  support'

Signed-off-by: Tomi Valkeinen <tomi.valkei...@ideasonboard.com>
---
  drivers/gpu/drm/bridge/tc358768.c | 56 +++++++++++++------------------
  1 file changed, 24 insertions(+), 32 deletions(-)

diff --git a/drivers/gpu/drm/bridge/tc358768.c 
b/drivers/gpu/drm/bridge/tc358768.c
index 82ea4d9a814a..9705ce1bd028 100644
--- a/drivers/gpu/drm/bridge/tc358768.c
+++ b/drivers/gpu/drm/bridge/tc358768.c
@@ -455,8 +455,6 @@ static int tc358768_dsi_host_detach(struct mipi_dsi_host 
*host,
        struct tc358768_priv *priv = dsi_host_to_tc358768(host);
  
  	drm_bridge_remove(&priv->bridge);
-       if (priv->output.panel)
-               drm_panel_bridge_remove(priv->output.next_bridge);
  
  	return 0;
  }
@@ -531,49 +529,42 @@ static int tc358768_bridge_attach(struct drm_bridge 
*bridge,
                                  enum drm_bridge_attach_flags flags)
  {
        struct tc358768_priv *priv = bridge_to_tc358768(bridge);
+       struct drm_bridge *next_bridge;
+       struct drm_panel *panel;
+       int ret;
  
  	if (!drm_core_check_feature(bridge->dev, DRIVER_ATOMIC)) {
                dev_err(priv->dev, "needs atomic updates support\n");
                return -ENOTSUPP;
        }
  
-	if (flags & DRM_BRIDGE_ATTACH_NO_CONNECTOR) {
-               struct device_node *node;
-
-               /* Get the next bridge, connected to port@1. */
-               node = of_graph_get_remote_node(priv->dev->of_node, 1, -1);
-               if (!node)
-                       return -ENODEV;
-
-               priv->output.next_bridge = of_drm_find_bridge(node);
-               of_node_put(node);
-               if (!priv->output.next_bridge)
-                       return -EPROBE_DEFER;
-       } else {
-               struct drm_bridge *bridge;
-               struct drm_panel *panel;
-               int ret;
-
-               ret = drm_of_find_panel_or_bridge(priv->dev->of_node, 1, 0,
-                                                 &panel, &bridge);
-               if (ret)
-                       return ret;
-
-               if (panel) {
-                       bridge = drm_panel_bridge_add_typed(panel,
-                               DRM_MODE_CONNECTOR_DSI);
-                       if (IS_ERR(bridge))
-                               return PTR_ERR(bridge);
-               }
+       ret = drm_of_find_panel_or_bridge(priv->dev->of_node, 1, -1, &panel,
+                                         &next_bridge);

I think the right way is to wrap the panel in a bridge,
so something like:

        next_bridge = devm_drm_of_get_bridge(dev, priv->dev->of_node, 1, -1)

        if (IS_ERR(next_bridge))
                return ...
        priv->output.next_bridge = next_bridge;

I tried that, but I had trouble with the cleanup side.

In the fixup patch I attached in my reply to Maxim I used 
drm_of_find_panel_or_bridge() + drm_panel_bridge_add_typed(), and on 
bridge_detach callback I used drm_panel_bridge_remove() (if there is a 
panel). This worked for me, but it does feel like a bit too much work 
for a driver to do.

 Tomi