Cut and paste this URL to share the unmodified register and value:
https://regviz.com/r/Silicon Labs/Series1/EFM32GG11B/EFM32GG11B420F2048IL112/USB/GRXFSIZ#0x0
Receive FIFO Size Register
RxFIFO Depth
https://github.com/cmsis-svd/cmsis-svd-data