Cut and paste this URL to share the unmodified register and value:
https://regviz.com/r/Silicon Labs/Series1/EFR32MG12P/EFR32MG12P432F1024IM48/USART0/CLKDIV#0x0
Clock Control Register
Fractional Clock Divider
AUTOBAUD Detection Enable
https://github.com/cmsis-svd/cmsis-svd-data