I found another way to solve my problem, maybe this solution is not what you are thinking.
Considering the USB 2.0 is still not working, and the USB 3.0/3.1 works just fine, I decide not to make further endeavor on USB 2.0.
I brought a cable which is an adapter between usb 2.0 and 3.0, it is like this picture. And I connect the usb 2.0 port to the usb 3.0 port of my motherboard.
It then works successfully.
Now my bluetooth is working because it needs a onboard usb 2.0 port.
Hope my experience would bring you some ideas.
I am asking for instruction for my newly installed system.
I fellow the instruction:https://vanilla.amd-osx.com/ to install my macOS, everything works fine except all USB 2.0 ports. It seems that the USB 2.0 controller is not recognized by the system. I tried this instruction:viewtopic.php?f=24&t=4986([NEW] NATIVE USB SUPPORT [RYZEN CPUS ONLY]), but did not work as well.
Is there anyone who is facing the same problem?
Is there any kind person who would like to help me with the USB 2.0 ports?
Thank you very much!!!!
UPDATE(20190518): Updating to 10.14.5 is also tried, the system works fine with new patches and nothing changes. All functions except usb 2.0 ports are fine...
Motherboard: Asrock X370 taichi
CPU: Ryzen 1700X