Re: [PATCH v2 07/12] drm/bridge: analogix_dp: Add support to find panel or bridge

["Heiko Stübner" <heiko@sntech.de>]

Hi Damon,

Am Mittwoch, 9. Juli 2025, 09:01:34 Mitteleuropäische Sommerzeit schrieb Damon Ding:
> Since the panel/bridge should logically be positioned behind the
> Analogix bridge in the display pipeline, it makes sense to handle
> the panel/bridge parsing on the Analogix side.
> 
> Signed-off-by: Damon Ding <damon.ding@rock-chips.com>
> ---
>  .../drm/bridge/analogix/analogix_dp_core.c    | 48 +++++++++++++++++++
>  include/drm/bridge/analogix_dp.h              |  2 +
>  2 files changed, 50 insertions(+)
> 
> diff --git a/drivers/gpu/drm/bridge/analogix/analogix_dp_core.c b/drivers/gpu/drm/bridge/analogix/analogix_dp_core.c
> index 78d68310e4f6..660f95e90490 100644
> --- a/drivers/gpu/drm/bridge/analogix/analogix_dp_core.c
> +++ b/drivers/gpu/drm/bridge/analogix/analogix_dp_core.c
> @@ -19,12 +19,14 @@
>  #include <linux/platform_device.h>
>  
>  #include <drm/bridge/analogix_dp.h>
> +#include <drm/display/drm_dp_aux_bus.h>
>  #include <drm/drm_atomic.h>
>  #include <drm/drm_atomic_helper.h>
>  #include <drm/drm_bridge.h>
>  #include <drm/drm_crtc.h>
>  #include <drm/drm_device.h>
>  #include <drm/drm_edid.h>
> +#include <drm/drm_of.h>
>  #include <drm/drm_panel.h>
>  #include <drm/drm_print.h>
>  #include <drm/drm_probe_helper.h>
> @@ -1707,6 +1709,52 @@ struct drm_dp_aux *analogix_dp_get_aux(struct analogix_dp_device *dp)
>  }
>  EXPORT_SYMBOL_GPL(analogix_dp_get_aux);
>  
> +static int analogix_dp_aux_done_probing(struct drm_dp_aux *aux)
> +{
> +	struct analogix_dp_device *dp = to_dp(aux);
> +	struct analogix_dp_plat_data *plat_data = dp->plat_data;
> +	int port = plat_data->dev_type == EXYNOS_DP ? 0 : 1;
> +	int ret;
> +
> +	/*
> +	 * If drm_of_find_panel_or_bridge() returns -ENODEV, there may be no valid panel
> +	 * or bridge nodes. The driver should go on for the driver-free bridge or the DP
> +	 * mode applications.
> +	 */
> +	ret = drm_of_find_panel_or_bridge(dp->dev->of_node, port, 0,
> +					  &plat_data->panel, &plat_data->bridge);

Could you check if this can use a panel-bridge?
See for example 
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/gpu/drm/rockchip/rockchip_rgb.c#n138
or a lot of other places for drm_panel_bridge_add()

So if drm_of_find_panel_or_bridge() finds a bridge, just use it; if it
finds a panel, drm_panel_bridge_add() just wraps a bridge around it
and all the code can just assume everything is bridge after that.



> +	if (ret && ret != -ENODEV)
> +		return ret;
> +
> +	return component_add(dp->dev, plat_data->ops);
> +}
> +
> +int analogix_dp_find_panel_or_bridge(struct analogix_dp_device *dp)
> +{
> +	int ret;
> +
> +	ret = devm_of_dp_aux_populate_bus(&dp->aux, analogix_dp_aux_done_probing);
> +	if (ret) {
> +		/*
> +		 * If devm_of_dp_aux_populate_bus() returns -ENODEV, the done_probing() will
> +		 * not be called because there are no EP devices. Then the callback function
> +		 * analogix_dp_aux_done_probing() will be called directly in order to support
> +		 * the other valid DT configurations.
> +		 *
> +		 * NOTE: The devm_of_dp_aux_populate_bus() is allowed to return -EPROBE_DEFER.
> +		 */
> +		if (ret != -ENODEV) {
> +			dev_err(dp->dev, "failed to populate aux bus\n");
> +			return ret;
> +		}
> +
> +		return analogix_dp_aux_done_probing(&dp->aux);
> +	}
> +
> +	return 0;
> +}
> +EXPORT_SYMBOL_GPL(analogix_dp_find_panel_or_bridge);
> +
>  MODULE_AUTHOR("Jingoo Han <jg1.han@samsung.com>");
>  MODULE_DESCRIPTION("Analogix DP Core Driver");
>  MODULE_LICENSE("GPL v2");
> diff --git a/include/drm/bridge/analogix_dp.h b/include/drm/bridge/analogix_dp.h
> index 202e5eafb2cc..0b6d85f1924e 100644
> --- a/include/drm/bridge/analogix_dp.h
> +++ b/include/drm/bridge/analogix_dp.h
> @@ -30,6 +30,7 @@ struct analogix_dp_plat_data {
>  	struct drm_bridge *bridge;
>  	struct drm_encoder *encoder;
>  	struct drm_connector *connector;
> +	const struct component_ops *ops;
>  
>  	int (*power_on)(struct analogix_dp_plat_data *);
>  	int (*power_off)(struct analogix_dp_plat_data *);
> @@ -52,5 +53,6 @@ int analogix_dp_stop_crc(struct drm_connector *connector);
>  
>  struct analogix_dp_plat_data *analogix_dp_aux_to_plat_data(struct drm_dp_aux *aux);
>  struct drm_dp_aux *analogix_dp_get_aux(struct analogix_dp_device *dp);
> +int analogix_dp_find_panel_or_bridge(struct analogix_dp_device *dp);
>  
>  #endif /* _ANALOGIX_DP_H_ */
>