Cut and paste this URL to share the unmodified register and value:
https://regviz.com/r/Atmel/ATSAMA5D31/SFR/UTMICKTRIM#0x0
FREQ=12
UTMI Clock Trimming Register
UTMI Reference Clock Frequency
0 (12): 12 MHz reference clock
1 (16): 16 MHz reference clock
2 (24): 24 MHz reference clock
3 (48): 48 MHz reference clock
UTMI Band Gap Voltage Trimming
https://github.com/cmsis-svd/cmsis-svd-data