Cut and paste this URL to share the unmodified register and value:
https://regviz.com/r/Silicon Labs/Series1/EFM32GG11B/EFM32GG11B820F2048IL152/ETM/ETMFFLR#0x0
ETM Fifo Full Level Register
Bytes left in FIFO
https://github.com/cmsis-svd/cmsis-svd-data