Cut and paste this URL to share the unmodified register and value:
https://regviz.com/r/Silicon Labs/Series1/EFM32GG12B/EFM32GG12B410F1024GM64/SDIO/BOOTTOCTRL#0x0
Boot Timeout Control Register
Boot Data Timeout Counter Value
https://github.com/cmsis-svd/cmsis-svd-data