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

[Damon Ding <damon.ding@rock-chips.com>]

Hi Heiko,

On 2025/7/10 4:07, Heiko Stübner wrote:
> 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.
> 
> 

Yes, that is a good approach. Using the panel-bridge will make the 
related checks more concise.

> 
>> +	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_ */
>>
> 

Best regards,
Damon