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

[Marek Szyprowski <m.szyprowski@samsung.com>]

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.


>
> 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
>
>
Best regards
-- 
Marek Szyprowski, PhD
Samsung R&D Institute Poland