Re: [PATCH v3 0/5] Add Type-C DP support for RK3399 EVB IND board

Dmitry Baryshkov
2025-07-30T19:13:58Z

On Tue, Jul 29, 2025 at 05:00:27PM +0800, 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.
>

[....]

> ====
> 2. DP HPD event notify
>
> 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 ---+

Could you please clarify this, can you switch DP stream between two
USB-C outputs? What happens if user plugs in DP dongles in both USB-C
ports?

>
> BTW, one of the important things to do is to implement extcon-like
> notifications. I found include/drm/bridge/aux-bridge.h , but if the
> aux-bridge is used, the bridge chain would look like this:
>
> PHY0 aux-bridge ---+
> | ----> CDN-DP bridge
> PHY1 aux-bridge ---+
>
> Oh, CDN-DP bridge has two previous aux-bridge!
>
> Now, I try to use drm_connector_oob_hotplug_event() to notify HPD
> state between PHY and CDN-DP controller.

Does it actually work? The OOB HPD event will be repoted for the usb-c
connector's fwnode, but the DP controller isn't connected to that node
anyhow. If I'm not mistaken, the HPD signal will not reach DP driver in
this case.

>
> Patch1 add new Type-C mode switch for RK3399 USBDP phy binding.
> Patch2 add typec_mux and typec_switch for RK3399 USBDP PHY.
> Patch3 drops CDN-DP's extcon dependency when Type-C is present.
> Patch4 add missing dp_out port for RK3399 CDN-DP.
> Patch5 add Type-C DP support for RK3399 EVB IND board.
>

--
With best wishes
Dmitry