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 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


 > ...

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