The original default operating frequency for hte Morello boards was set at 2300MHz by the firmware on reset. With the latest release of the board firmware this has been raised to 2500MHz.
2.1.1. Morello Development Board specific Features
The frequency can be checked in the SCP log as
0.955910] [MORELLO SYSTEM] Booting primary core at 2500 MHz...
If the log is showing a value of 2300MHz then it is recommended that you update to the latest version of board firmware