How to change USB 3.0 to USB 2.0 just by changing kernel source? (TX2)

Hi,
In general, you need USB2 and USB3 pins to form a USB3 type-A port. You can disable USB3 in device tree. Take this post for example:

usb2-1 and usb3-1 are paired to be USB3 type-A port. To run USB2 only, you can set usb3-1

status = "disabled";