Message-ID: <e1b172bd-443f-40a5-9d9e-9e575b0b551e@rock-chips.com>
Date: Mon, 26 Jan 2026 11:22:04 +0800
From: Chaoyi Chen <chaoyi.chen@...k-chips.com>
To: Hugh Cole-Baker <sigmaris@...il.com>
Cc: Chaoyi Chen <kernel@...kyi.com>,
 Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
 Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
 Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>,
 Peter Chen <hzpeterchen@...il.com>, Luca Ceresoli
 <luca.ceresoli@...tlin.com>, Rob Herring <robh@...nel.org>,
 Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley
 <conor+dt@...nel.org>, Vinod Koul <vkoul@...nel.org>,
 Kishon Vijay Abraham I <kishon@...nel.org>, Heiko Stuebner
 <heiko@...ech.de>, Sandy Huang <hjc@...k-chips.com>,
 Andy Yan <andy.yan@...k-chips.com>,
 Yubing Zhang <yubing.zhang@...k-chips.com>,
 Frank Wang <frank.wang@...k-chips.com>,
 Andrzej Hajda <andrzej.hajda@...el.com>,
 Neil Armstrong <neil.armstrong@...aro.org>, Robert Foss <rfoss@...nel.org>,
 Laurent Pinchart <Laurent.pinchart@...asonboard.com>,
 Jonas Karlman <jonas@...boo.se>, Jernej Skrabec <jernej.skrabec@...il.com>,
 Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
 Maxime Ripard <mripard@...nel.org>, Thomas Zimmermann <tzimmermann@...e.de>,
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 Amit Sunil Dhamne <amitsd@...gle.com>, Dragan Simic <dsimic@...jaro.org>,
 Johan Jonker <jbx6244@...il.com>, Diederik de Haas <didi.debian@...ow.org>,
 Peter Robinson <pbrobinson@...il.com>, linux-usb@...r.kernel.org,
 devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
 linux-phy@...ts.infradead.org, linux-arm-kernel@...ts.infradead.org,
 linux-rockchip@...ts.infradead.org, dri-devel@...ts.freedesktop.org
Subject: Re: [PATCH v14 0/9] Add Type-C DP support for RK3399 EVB IND board

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@...k-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@...il.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 :)

-- 
Best, 
Chaoyi

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