Re: [PATCH v3 17/19] drm/omap: dss: don't create a panel_bridge

[Andreas Kemnade <andreas@kemnade.info>]

On Wed, 16 Sep 2026 15:45:41 +0200
Luca Ceresoli <luca.ceresoli@bootlin.com> wrote:

> Now a panel_bridge is automatically created for every drm_panel and the
> panel-bridge API is just a deprecated wrapper to access it.
> 
> Update and simplify the code by just getting a reference to the
> already-existing bridge using of_drm_get_bridge_by_endpoint().
> 
> Signed-off-by: Luca Ceresoli <luca.ceresoli@bootlin.com>

This breaks the display on GTA04/OMAPDRM.

Panel is panel-tpo-td028ttec1 attached via DPI, controlled
via spi_gpio.

I get
[   12.050201] omapdrm omapdrm.0: [drm] No compatible format found
[   12.050231] omapdrm omapdrm.0: [drm] Cannot find any crtc or sizes

Workaround:
rmmod omapdrm
modprobe omapdrm

Regards,
Andreas

> ---
>  drivers/gpu/drm/omapdrm/dss/omapdss.h |  1 -
>  drivers/gpu/drm/omapdrm/dss/output.c  | 42 ++++-------------------------------
>  2 files changed, 4 insertions(+), 39 deletions(-)
> 
> diff --git a/drivers/gpu/drm/omapdrm/dss/omapdss.h b/drivers/gpu/drm/omapdrm/dss/omapdss.h
> index 4c22c09c93d5..e3e685c931f1 100644
> --- a/drivers/gpu/drm/omapdrm/dss/omapdss.h
> +++ b/drivers/gpu/drm/omapdrm/dss/omapdss.h
> @@ -204,7 +204,6 @@ struct omap_dss_device {
>  	struct dss_device *dss;
>  	struct drm_bridge *bridge;
>  	struct drm_bridge *next_bridge;
> -	struct drm_panel *panel;
>  
>  	struct list_head list;
>  
> diff --git a/drivers/gpu/drm/omapdrm/dss/output.c b/drivers/gpu/drm/omapdrm/dss/output.c
> index 6e9bc605ee22..36d37deac802 100644
> --- a/drivers/gpu/drm/omapdrm/dss/output.c
> +++ b/drivers/gpu/drm/omapdrm/dss/output.c
> @@ -12,7 +12,6 @@
>  #include <linux/of_graph.h>
>  
>  #include <drm/drm_bridge.h>
> -#include <drm/drm_panel.h>
>  
>  #include "dss.h"
>  #include "omapdss.h"
> @@ -20,40 +19,16 @@
>  int omapdss_device_init_output(struct omap_dss_device *out,
>  			       struct drm_bridge *local_bridge)
>  {
> -	struct device_node *remote_node;
> +	struct drm_bridge *bridge;
>  	int ret;
>  
> -	remote_node = of_graph_get_remote_node(out->dev->of_node,
> -					       out->of_port, 0);
> -	if (!remote_node) {
> +	bridge = of_drm_get_bridge_by_endpoint(out->dev->of_node, out->of_port, 0);
> +	if (IS_ERR(bridge)) {
>  		dev_dbg(out->dev, "failed to find video sink\n");
>  		return 0;
>  	}
>  
> -	out->panel = of_drm_find_panel(remote_node);
> -	if (IS_ERR(out->panel))
> -		out->panel = NULL;
> -
> -	if (!out->panel)
> -		out->bridge = of_drm_find_and_get_bridge(remote_node);
> -
> -	of_node_put(remote_node);
> -
> -	if (out->panel) {
> -		struct drm_bridge *bridge;
> -
> -		bridge = drm_panel_bridge_add(out->panel);
> -		drm_panel_put(out->panel);
> -		if (IS_ERR(bridge)) {
> -			dev_err(out->dev,
> -				"unable to create panel bridge (%ld)\n",
> -				PTR_ERR(bridge));
> -			ret = PTR_ERR(bridge);
> -			goto error;
> -		}
> -
> -		out->bridge = drm_bridge_get(bridge);
> -	}
> +	out->bridge = bridge;
>  
>  	if (local_bridge) {
>  		if (!out->bridge) {
> @@ -65,11 +40,6 @@ int omapdss_device_init_output(struct omap_dss_device *out,
>  		out->bridge = drm_bridge_get(local_bridge);
>  	}
>  
> -	if (!out->bridge) {
> -		ret = -EPROBE_DEFER;
> -		goto error;
> -	}
> -
>  	return 0;
>  
>  error:
> @@ -79,10 +49,6 @@ int omapdss_device_init_output(struct omap_dss_device *out,
>  
>  void omapdss_device_cleanup_output(struct omap_dss_device *out)
>  {
> -	if (out->bridge && out->panel)
> -		drm_panel_bridge_remove(out->next_bridge ?
> -					out->next_bridge : out->bridge);
> -
>  	drm_bridge_put(out->next_bridge);
>  	drm_bridge_put(out->bridge);
>  }
>