We are using USB port(USB0 + UPHY Lane1) in the following image.
My understanding is that the USB port will operate in USB2.0(USB0) and USB3.0(UPHY Lane1) modes.
When the port will be operated in USB2.0 mode and when in USB3.0 modes? I need to reduce the speed in USB3.0 mode. Can you guide how I can change the speed of USB3.0?
The behavior follows USB spec. When a device is connected, it tries to enumerate USB3. If it fails, it then tries to enumerate USB2. For USB3.0, the bandwidth is 5Gbps and it is not supported to cap the bandwidth to certain value(such as 2Gbps).
If you exclude the extra wiring of USB3, then it might try to enumerate as USB3, but it would fail and try to enumerate as USB2.