USB Dual Role Support - eXtensible Device Controller Interface (xDCI) Controller

The USB subsystem also supports Dual Role Capability. The xHCI is paired with a standalone eXtensible Device Controller Interface (xDCI) to provide dual role functionality. The USB subsystem incorporates a xDCI USB 3.2 Gen 1x1 (5 Gb/s) device controller. The Dual Role capability splits the support for SuperSpeed USB 5 Gbps on the CPU xDCI controller, and High-Speed (HS) on the PCH xDCI controller. These controllers are instantiated as a separate PCI function. The USB implementation is compliant to the Device specification and supports host/device only through the USB Type-C* connector.

The xDCI shares all USB ports with the host controller, with the ownership of the port being decided based the USB Power Delivery specification. Since all the ports support device mode, xDCI enabling must be extended by System BIOS and EC. While the port is mapped to the device controller, the host controller Rx detection must always indicate a disconnected port. Only one port can be connected (and active) to the device controller at one time. Any subsequently connection will not be established.