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 8/29/2025 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);

Best regards,
Damon