Re: [PATCH v4 00/13] Apply drm_bridge_connector and panel_bridge helper for the Analogix DP driver

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

Hi Marek,

On 2025/8/15 5:16, Marek Szyprowski wrote:
> 
> On 14.08.2025 16:33, Marek Szyprowski wrote:
>> On 14.08.2025 12:47, Damon Ding wrote:
>>> PATCH 1 is a small format optimization for struct analogid_dp_device.
>>> PATCH 2 is to perform mode setting in &drm_bridge_funcs.atomic_enable.
>>> PATCH 3-6 are preparations for apply drm_bridge_connector helper.
>>> PATCH 7 is to apply the drm_bridge_connector helper.
>>> PATCH 8-10 are to move the panel/bridge parsing to the Analogix side.
>>> PATCH 11-12 are preparations for apply panel_bridge helper.
>>> PATCH 13 is to apply the panel_bridge helper.
>>
>> This series lacks 'select DRM_BRIDGE_CONNECTOR' in ExynosDP's Kconfig,
>> so it causes build break:
>>
>> drivers/gpu/drm/exynos/exynos_dp.c:177: undefined reference to
>> `drm_bridge_connector_init'
>> make[2]: *** [scripts/Makefile.vmlinux:91: vmlinux] Error 1
>>
>> After adding this dependency, the Exynos DP driver stops working. On
>> Samsung Snow Chromebook I observed following issue:
>>
>> [    4.534220] exynos-dp 145b0000.dp-controller: failed to attach
>> following panel or bridge (-16)
>> [    4.543428] exynos-drm exynos-drm: failed to bind
>> 145b0000.dp-controller (ops exynos_dp_ops): -16
>> [    4.551775] exynos-drm exynos-drm: adev bind failed: -16
>> [    4.556559] exynos-dp 145b0000.dp-controller: probe with driver
>> exynos-dp failed with error -16
>>
>> I will investigate details later in the evening.
> 
> The failure is caused by trying to add plat_data->next_bridge twice
> (from exynos_dp's .attach callback, and from analogix' ->bind callback).
> 
> 
> Best regards

I see. The bridge attachment for the next bridge was not well thought 
out. It may be better to move panel_bridge addition a little forward and 
remove next_bridge attachment on the Analogix side. Then, the Rockchip 
side and Exynos side can do their own next_bridge attachment in 
&analogix_dp_plat_data.attach() as they want.

Could you please help test the following modifications(they have been 
tested on my RK3588S EVB1 Board) on the Samsung Snow Chromebook? ;-)

diff --git a/drivers/gpu/drm/bridge/analogix/analogix_dp_core.c 
b/drivers/gpu/drm/bridge/analogix/analogix_dp_core.c
index 0529bfb02884..8a9ce1f31678 100644
--- a/drivers/gpu/drm/bridge/analogix/analogix_dp_core.c
+++ b/drivers/gpu/drm/bridge/analogix/analogix_dp_core.c
@@ -1573,6 +1573,15 @@ int analogix_dp_bind(struct analogix_dp_device 
*dp, struct drm_device *drm_dev)
                 return ret;
         }

+       if (dp->plat_data->panel) {
+               dp->plat_data->next_bridge = 
devm_drm_panel_bridge_add(dp->dev,
+ 
dp->plat_data->panel);
+               if (IS_ERR(dp->plat_data->next_bridge)) {
+                       ret = PTR_ERR(bridge);
+                       goto err_unregister_aux;
+               }
+       }
+
         bridge->ops = DRM_BRIDGE_OP_DETECT |
                       DRM_BRIDGE_OP_EDID |
                       DRM_BRIDGE_OP_MODES;
@@ -1588,22 +1597,6 @@ int analogix_dp_bind(struct analogix_dp_device 
*dp, struct drm_device *drm_dev)
                 goto err_unregister_aux;
         }

-       if (dp->plat_data->panel) {
-               dp->plat_data->next_bridge = 
devm_drm_panel_bridge_add(dp->dev,
- 
dp->plat_data->panel);
-               if (IS_ERR(dp->plat_data->next_bridge)) {
-                       ret = PTR_ERR(bridge);
-                       goto err_unregister_aux;
-               }
-       }
-
-       ret = drm_bridge_attach(dp->encoder, dp->plat_data->next_bridge, 
bridge,
-                               DRM_BRIDGE_ATTACH_NO_CONNECTOR);
-       if (ret) {
-               dev_err(dp->dev, "failed to attach following panel or 
bridge (%d)\n", ret);
-               goto err_unregister_aux;
-       }
-
         return 0;

  err_unregister_aux:
diff --git a/drivers/gpu/drm/exynos/exynos_dp.c 
b/drivers/gpu/drm/exynos/exynos_dp.c
index 80ba700d2964..d0422f940249 100644
--- a/drivers/gpu/drm/exynos/exynos_dp.c
+++ b/drivers/gpu/drm/exynos/exynos_dp.c
@@ -104,7 +104,7 @@ static int exynos_dp_bridge_attach(struct 
analogix_dp_plat_data *plat_data,
         /* Pre-empt DP connector creation if there's a bridge */
         if (plat_data->next_bridge) {
                 ret = drm_bridge_attach(&dp->encoder, 
plat_data->next_bridge, bridge,
-                                       0);
+                                       DRM_BRIDGE_ATTACH_NO_CONNECTOR);
                 if (ret)
                         return ret;
         }
diff --git a/drivers/gpu/drm/rockchip/analogix_dp-rockchip.c 
b/drivers/gpu/drm/rockchip/analogix_dp-rockchip.c
index 0862b09a8be2..dfd32a79b94f 100644
--- a/drivers/gpu/drm/rockchip/analogix_dp-rockchip.c
+++ b/drivers/gpu/drm/rockchip/analogix_dp-rockchip.c
@@ -164,6 +164,24 @@ static int rockchip_dp_powerdown(struct 
analogix_dp_plat_data *plat_data)
         return 0;
  }

+static int rockchip_dp_attach(struct analogix_dp_plat_data *plat_data,
+                                    struct drm_bridge *bridge)
+{
+       struct rockchip_dp_device *dp = pdata_encoder_to_dp(plat_data);
+       int ret;
+
+       if (plat_data->next_bridge) {
+               ret = drm_bridge_attach(&dp->encoder.encoder, 
plat_data->next_bridge, bridge,
+                                       DRM_BRIDGE_ATTACH_NO_CONNECTOR);
+               if (ret) {
+                       dev_err(dp->dev, "failed to attach following 
panel or bridge (%d)\n", ret);
+                       return ret;
+               }
+       }
+
+       return 0;
+}
+
  static int rockchip_dp_get_modes(struct analogix_dp_plat_data *plat_data,
                                  struct drm_connector *connector)
  {
@@ -478,6 +496,7 @@ static int rockchip_dp_probe(struct platform_device 
*pdev)
         dp->plat_data.dev_type = dp->data->chip_type;
         dp->plat_data.power_on = rockchip_dp_poweron;
         dp->plat_data.power_off = rockchip_dp_powerdown;
+       dp->plat_data.attach = rockchip_dp_attach;
         dp->plat_data.get_modes = rockchip_dp_get_modes;
         dp->plat_data.ops = &rockchip_dp_component_ops;


Best regards,
Damon