USB-C DisplayPort Alt Mode on Rockchip RK3588/RK3576, Starting with Flipper One
2 days ago
- Partnership with Flipper to support USB-C DisplayPort AltMode on Flipper One, demo at OSS+ELC EU 2026.
- USB-PD protocol negotiates power, data roles, and alternate modes; uses CC pins for communication and determines orientation.
- Rockchip SoCs integrate a combined USBDP PHY for USB3 and DisplayPort, enabling flexible pin multiplexing without external components.
- External USB-PD controller (e.g., FUSB302) is managed by TCPM state machine in kernel, which handles power negotiation and AltMode discovery.
- Device tree configuration links USB-C connector, USBDP PHY, and controllers; includes SVID/VDM for DisplayPort AltMode.
- After negotiation, TCPM requests AltMode entry, which routes pins via USBDP to DP or USB3, and handles hotplug via PD protocol instead of physical pin.
- Software architecture uses DRM bridge chain (USB-C controller -> USBDP -> DP controller) to handle hotplug and power sequencing.
- DP AUX channel uses SBU pins for link training; status and EDID available in sysfs.
- Patches for USB controller are mainlined; USBDP PHY and DRM parts are in review; community testing helps upstream.