Cut and paste this URL to share the unmodified register and value:
https://regviz.com/r/Silicon Labs/Series1/EFM32GG12B/EFM32GG12B310F1024GQ100/ETM/ETMSYNCFR#0x0
Synchronisation Frequency Register
Synchronisation Frequency Value
https://github.com/cmsis-svd/cmsis-svd-data