Re: [PATCH v14 0/9] Add Type-C DP support for RK3399 EVB IND board

[Chaoyi Chen <chaoyi.chen@rock-chips.com>]

On 1/26/2026 11:22 AM, Chaoyi Chen wrote:
> Hello,
> 
> On 1/26/2026 3:42 AM, Hugh Cole-Baker wrote:
>> On 19/01/2026 07:30, Chaoyi Chen wrote:
>>> From: Chaoyi Chen <chaoyi.chen@rock-chips.com>
>>>
>>> This series focuses on adding Type-C DP support for USBDP PHY and DP
>>> driver. The USBDP PHY and DP will perceive the changes in cable status
>>> based on the USB PD and Type-C state machines provided by TCPM. Before
>>> this, the USBDP PHY and DP controller of RK3399 sensed cable state
>>> changes through extcon, and devices such as the RK3399 Gru-Chromebook
>>> rely on them. This series should not break them.
>>>
>>> ====
>>> 1. DisplayPort HPD status notify
>>>
>>> Before v7, I implemented a variety of DP HPD status notify. However,
>>> they all had various problems and it was difficult to become a generic
>>> solution.
>>>
>>> Under the guidance of Heikki and Dmitry, a decoupled notification
>>> method between the TypeC and DRM subsystems was introduced in v7.
>>> First, a notification is sent when TypeC registers a new altmode.
>>> Then, a generic DP AUX HPD bridge is implemented on the DRM side.
>>>
>>> During v7-v10, we added a new notifier in typec to notify the altmode
>>> device register event. With the help of Greg and Heikki, we implemented
>>> the reuse of notifiers for the type bus itself in patch1 of v11.
>>>
>>> The USB subsystem related parts have already been merged into the
>>> usb-next branch in v13 [0][1]. Therefore, this series no longer includes
>>> these patches starting from v14. Thanks to Greg and Heikki!
>>>
>>> [0]: https://git.kernel.org/pub/scm/linux/kernel/git/gregkh/usb.git/commit/?h=usb-next&id=67ab45426215c7fdccb65aecd4cac15bbe4dfcbb
>>> [1]: https://git.kernel.org/pub/scm/linux/kernel/git/gregkh/usb.git/commit/?h=usb-next&id=4dee13db29de6dd869af9b3827e1ff569644e838
>>>
>>> That makes it redundant for each Type-C controller driver to implement
>>> a similar DP AUX HPD bridge in embedded scenarios.
>>>
>>> ====
>>> 2. Altmode switching and orientation switching for USBDP PHY
>>>
>>> For USB Type-C interfaces, an external Type-C controller chip assists
>>> by detecting cable attachment, determining plug orientation, and
>>> reporting USB PD message. The USB/DP combo PHY supports software
>>> configurable pin mapping and DisplayPort lane assignment. Based on
>>> these message, the combo PHY can perform both altmode switching and
>>> orientation switching via software.
>>>
>>> The RK3399 EVB IND board has a Type-C interface DisplayPort. It use
>>> fusb302 chip as Type-C controller. The connection diagram is shown below:
>>>
>>> fusb302 chip +---> USB2.0 PHY ----> DWC3 USB controller
>>>              |
>>>              +---> USB/DP PHY0 +--> CDN-DP controller
>>>                                |
>>>                                +--> DWC3 USB controller
>>>
>>> ====
>>> 3. Multiple bridge model for RK3399 CDN-DP
>>>
>>> The RK3399 has two USB/DP combo PHY and one CDN-DP controller. And
>>> the CDN-DP can be switched to output to one of the PHYs.
>>>
>>> USB/DP PHY0 ---+
>>>                | <----> CDN-DP controller
>>> USB/DP PHY1 ---+
>>>
>>> In previous versions, if both PHY ports were connected to DP,
>>> the CDN-DP driver would select the first PHY port for output.
>>>
>>> On Dmitry's suggestion, we introduced a multi-bridge model to support
>>> flexible selection of the output PHY port. For each PHY port, a
>>> separate encoder and bridge are registered.
>>>
>>> The change is based on the DRM AUX HPD bridge, rather than the
>>> extcon approach. This requires the DT to correctly describe the
>>> connections between the first bridge in bridge chain and DP
>>> controller. And Once the first bridge is obtained, we can get the
>>> last bridge corresponding to the USB-C connector, and then set the
>>> DRM connector's fwnode to the corresponding one to enable HPD
>>> notification.
>>
>> With a similar dts patch [1] on top of this series I tested a type-C to
>> DP adapter/cable for display output on the ROCKPro64 board, which also
>> pairs a FUSB302 with RK3399. Booting it up with the cable plugged in
>> works, as does hotplugging the cable after booting in both orientations.
>> The correct mode for the display is detected. I wasn't able to test
>> audio, only video output, as this display doesn't have speakers.
>>
>> I did once, after unplugging and reconnecting the cable a few times,
>> see it get into a state where it didn't detect the attached display.
>> Logs from that unplug/reconnect attempt are here [2] if of interest.
>> Nevertheless, hotplug seems to work the majority of the time, so
>>
>> Tested-by: Hugh Cole-Baker <sigmaris@gmail.com>
>>
>> [1]: https://github.com/sigmaris/linux/commit/91724088b19bee7d248946442a801423e8cd0634
>> [2]: https://gist.github.com/sigmaris/fa107384a7492583ceee1c2962f5030a
>>
> 
> Thank you for the test. I also have the same board, and I will
> try it later :)
> 

I just tested on the ROCKPro64 board using a Type-C to HDMI dock,
and after repeatedly plugging and unplugging it over 30 times, 
it performed correctly every time :)

-- 
Best, 
Chaoyi