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 8/20/2025 5:20 AM, Marek Szyprowski wrote:
> On 15.08.2025 04:59, Damon Ding wrote:
>> 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? ;-)
> 
> Assuming that I properly applied the malformed diff, it doesn't solve
> all the issues. There are no errors reported though, but the display
> chain doesn't work and no valid mode is reported:
> 
> # dmesg | grep drm
> [    3.384992] [drm] Initialized panfrost 1.4.0 for 11800000.gpu on minor 0
> [    4.487739] [drm] Exynos DRM: using 14400000.fimd device for DMA
> mapping operations
> [    4.494202] exynos-drm exynos-drm: bound 14400000.fimd (ops
> fimd_component_ops)
> [    4.502374] exynos-drm exynos-drm: bound 14450000.mixer (ops
> mixer_component_ops)
> [    4.511930] exynos-drm exynos-drm: bound 145b0000.dp-controller (ops
> exynos_dp_ops)
> [    4.518411] exynos-drm exynos-drm: bound 14530000.hdmi (ops
> hdmi_component_ops)
> [    4.529628] [drm] Initialized exynos 1.1.0 for exynos-drm on minor 1
> [    4.657434] exynos-drm exynos-drm: [drm] Cannot find any crtc or sizes
> [    4.925023] exynos-drm exynos-drm: [drm] Cannot find any crtc or sizes
> 
> # ./modetest -c -Mexynos
> Connectors:
> id      encoder status          name            size (mm)       modes
>     encoders
> 69      0       disconnected    LVDS-1          0x0             0       68
>    props:
>          1 EDID:
>                  flags: immutable blob
>                  blobs:
> 
>                  value:
>          2 DPMS:
>                  flags: enum
>                  enums: On=0 Standby=1 Suspend=2 Off=3
>                  value: 0
>          5 link-status:
>                  flags: enum
>                  enums: Good=0 Bad=1
>                  value: 0
>          6 non-desktop:
>                  flags: immutable range
>                  values: 0 1
>                  value: 0
>          4 TILE:
>                  flags: immutable blob
>                  blobs:
> 
>                  value:
> 71      0       disconnected    HDMI-A-1        0x0             0       70
>    props:
>          1 EDID:
>                  flags: immutable blob
>                  blobs:
> 
>                  value:
>          2 DPMS:
>                  flags: enum
>                  enums: On=0 Standby=1 Suspend=2 Off=3
>                  value: 0
>          5 link-status:
>                  flags: enum
>                  enums: Good=0 Bad=1
>                  value: 0
>          6 non-desktop:
>                  flags: immutable range
>                  values: 0 1
>                  value: 0
>          4 TILE:
>                  flags: immutable blob
>                  blobs:
> 
>                  value:
> 
> 
> I will investigate details later this week.
> 

Could you please provide the related DTS file for the test? I will also 
try to find out the reason for this unexpected issue. ;-)

> 
>>
>> 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