Just a random person passing by. As one who is intimately familiar with the Synopsys USB IP... I am not sure if this is still an issue or not, but it seems like it is on this particular thread... (have not cross referenced any other threads).
Just looking at the USB register documentation in the first few replies. This IP is almost EXACTLY the same as the Synopsys USB IP found in all STM32 and EFM32 USB OTG peripherals. Not sure why nobody has noticed this? All register documentation and how to set up the peripheral are available in those relevant reference manuals. I have written several drivers for this IP myself.