[PATCH] drm/bridge: fsl-ldb: return -EPROBE_DEFER if the panel bridge is not found

[PATCH] drm/bridge: fsl-ldb: return -EPROBE_DEFER if the panel bridge is not found

[Dario Binacchi]

of_drm_find_and_get_bridge() returns NULL if the panel has not been
registered yet. Returning -ENODEV in this case makes the probe fail
instead of being retried, so the LDB is never bound and the display
pipeline never comes up:

  platform 32e90000.display-controller: deferred probe pending: imx-lcdif: Failed to get bridge for endpoint0

Return -EPROBE_DEFER, so that the probe is retried once the panel is
available.

Fixes: 802372cf316a ("drm/bridge: fsl-ldb: don't create a panel_bridge")
Signed-off-by: Dario Binacchi <dario.binacchi@amarulasolutions.com>

---

 drivers/gpu/drm/bridge/fsl-ldb.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/bridge/fsl-ldb.c b/drivers/gpu/drm/bridge/fsl-ldb.c
index 7ec84c81cd78..420b3e08130e 100644
--- a/drivers/gpu/drm/bridge/fsl-ldb.c
+++ b/drivers/gpu/drm/bridge/fsl-ldb.c
@@ -342,7 +342,7 @@ static int fsl_ldb_probe(struct platform_device *pdev)
 	fsl_ldb->bridge.next_bridge = of_drm_find_and_get_bridge(panel_node);
 	of_node_put(panel_node);
 	if (!fsl_ldb->bridge.next_bridge)
-		return -ENODEV;
+		return -EPROBE_DEFER;
 
 	if (fsl_ldb_is_dual(fsl_ldb)) {
 		struct device_node *port1, *port2;
---
base-commit: c339f4010dea8b0d754f84ace70cd1b089878ef8
branch: fsl-ldb-defer-probe

-- 
2.43.0

Re: [PATCH] drm/bridge: fsl-ldb: return -EPROBE_DEFER if the panel bridge is not found

[Laurentiu Palcu]

Hi Dario,

On Thu, Oct 29, 2026 at 03:41:28PM +0100, Dario Binacchi wrote:
> of_drm_find_and_get_bridge() returns NULL if the panel has not been
> registered yet. Returning -ENODEV in this case makes the probe fail
> instead of being retried, so the LDB is never bound and the display
> pipeline never comes up:
> 
>   platform 32e90000.display-controller: deferred probe pending: imx-lcdif: Failed to get bridge for endpoint0
> 
> Return -EPROBE_DEFER, so that the probe is retried once the panel is
> available.
> 
> Fixes: 802372cf316a ("drm/bridge: fsl-ldb: don't create a panel_bridge")
> Signed-off-by: Dario Binacchi <dario.binacchi@amarulasolutions.com>
> 
> ---
> 
>  drivers/gpu/drm/bridge/fsl-ldb.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/bridge/fsl-ldb.c b/drivers/gpu/drm/bridge/fsl-ldb.c
> index 7ec84c81cd78..420b3e08130e 100644
> --- a/drivers/gpu/drm/bridge/fsl-ldb.c
> +++ b/drivers/gpu/drm/bridge/fsl-ldb.c
> @@ -342,7 +342,7 @@ static int fsl_ldb_probe(struct platform_device *pdev)
>  	fsl_ldb->bridge.next_bridge = of_drm_find_and_get_bridge(panel_node);
>  	of_node_put(panel_node);
>  	if (!fsl_ldb->bridge.next_bridge)
> -		return -ENODEV;
> +		return -EPROBE_DEFER;

Hmm, I have a patch [1] in the DCIF series that adds support for non-panel
bridges to fsl-ldb.c which, indirectly, should fix this as well. But, since I
don't see that patchset merged anytime soon:

Reviewed-by: Laurentiu Palcu <laurentiu.palcu@oss.nxp.com>

[1] https://lore.kernel.org/dri-devel/20261006-dcif-upstreaming-v10-2-bcfb28de0aae@oss.nxp.com/

-- 
Thanks,
Laurentiu

Re: [PATCH] drm/bridge: fsl-ldb: return -EPROBE_DEFER if the panel bridge is not found

[Luca Ceresoli]

On Thu Oct 29, 2026 at 3:41 PM CET, Dario Binacchi wrote:
> of_drm_find_and_get_bridge() returns NULL if the panel has not been
> registered yet. Returning -ENODEV in this case makes the probe fail
> instead of being retried, so the LDB is never bound and the display
> pipeline never comes up:
>
>   platform 32e90000.display-controller: deferred probe pending: imx-lcdif: Failed to get bridge for endpoint0
>
> Return -EPROBE_DEFER, so that the probe is retried once the panel is
> available.
>
> Fixes: 802372cf316a ("drm/bridge: fsl-ldb: don't create a panel_bridge")
> Signed-off-by: Dario Binacchi <dario.binacchi@amarulasolutions.com>

Reviewed-by: Luca Ceresoli <luca.ceresoli@bootlin.com>

--
Luca Ceresoli, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com