Another useful tip for people that need to play with caravel clocks (DLL/DCO) to test frequencies is using the util:

/caravel_board/firmware/chipignite/util/caravel_hkdebug.py

You can modify the housekeeping registers with it (https://caravel-harness.readthedocs.io/en/latest/housekeeping-spi.html#housekeeping-spi-registers) and toggle DLL or DCO You don't need to upload the firmware so it's faster to test configurations. I was trying to understand the register values I needed to use in my firmware to run my design at 25mhz (with the 10mhz source clock from the board) and doing it with that util was really fast.