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 01.09.2025 05:41, Damon Ding wrote:
> On 8/29/2025 4:23 PM, Marek Szyprowski wrote:
>> On 29.08.2025 10:08, Damon Ding wrote:
>>> 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. ;-)
>>
>> Unfortunately I didn't find enough time to debug this further. The above
>> log is from Samsung Snow Chromebook,
>> arch/arm/boot/dts/samsung/exynos5250-snow.dts
>>
>>
>
> I compare the differences in the following display path before and 
> after this patch series:
>
> exynos_dp -> nxp-ptn3460 -> panel "auo,b116xw03"
>
> The issue is likely caused by the &drm_connector_funcs.detect() 
> related logic. Before this patch series, the nxp-ptn3460 connector is 
> always connector_status_connected because there is not available 
> &drm_connector_funcs.detect(). After it, the DRM_BRIDGE_OP_DETECT flag 
> make the connection status depend on analogix_dp_bridge_detect().
>
> Could you please add the following patches additionally and try again?
> (Not the final solution, just validation)
>
> diff --git a/drivers/gpu/drm/bridge/analogix/analogix_dp_core.c 
> b/drivers/gpu/drm/bridge/analogix/analogix_dp_core.c
> index a93ff8f0a468..355911c47354 100644
> --- a/drivers/gpu/drm/bridge/analogix/analogix_dp_core.c
> +++ b/drivers/gpu/drm/bridge/analogix/analogix_dp_core.c
> @@ -1491,9 +1491,11 @@ int analogix_dp_bind(struct analogix_dp_device 
> *dp, struct drm_device *drm_dev)
>                 }
>         }
>
> -       bridge->ops = DRM_BRIDGE_OP_DETECT |
> -                     DRM_BRIDGE_OP_EDID |
> +       bridge->ops = DRM_BRIDGE_OP_EDID |
>                       DRM_BRIDGE_OP_MODES;
> +       if (drm_bridge_is_panel(dp->plat_data->next_bridge))
> +               bridge->ops |= DRM_BRIDGE_OP_DETECT;
> +
>         bridge->of_node = dp->dev->of_node;
>         bridge->type = DRM_MODE_CONNECTOR_eDP;
>         ret = devm_drm_bridge_add(dp->dev, &dp->bridge);

It is better. Now the display panel is detected and reported to 
userspace, but it looks that something is not properly initialized, 
because there is garbage instead of the proper picture.

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