Setting the CPU frequency

I’m working bare-metal on the Rock Pi 4B. I use ARM’s PSCI to turn on the other CPUs after boot. They start with a low frequency. Sadly, PSCI only handles power on/off, not frequency scaling. For my use-case, I want all cores running at their max. speed. How can I set them to their max frequency?
I tried to get an idea from the Linux Kernel. My best guess so far is to enable the “right” values via the RK808 but I have no idea what these are and how to set them correctly.
Any help is greatly appreciated.

You can refer how to set the cpu freq from command line:

How to overclock the ROCK Pi 4B to 2Ghz:

Is it possible to overclock the Rock Pi 4?

Thank you @jack but this is not what I was looking fore because in my case I do not have linux running. So I need to talk to the hardware directly. My best guess right now is the RK808 power controller but I do not know the right values.

The frequency is set by the voltage to the ARM core, this is implemented by DVFS: