Kernel Scheduling effected by cpu scaling on frdm_mcxn236

[seankyer]

Describe the bug

I noticed when doing some development with the frdm_mcxn236 board that my threads would be scheduled sooner/later depending on what cpu frequency scaling the board was running with.

The actual UART output is fine, so that clock is remaining stable, but the system timer used for Kernel events seems to get scaled, which is against the requirements of cpu_freq integration.

This could just be a matter of choosing the kernel clock to be on a stable source for the SoC. But it must be fixed for the board to be usable with this subsystem.

Regression

• This is a regression.

Steps to reproduce

1. west build -p -b frdm_mcxn236 ./samples/subsys/cpu_freq/on_demand
2. Run on board
3. The logging shows timestamps from the sample, but the actual wall-clock time of the sample goes faster/slower depending on what pstate the SoC has chosen
4. UART output remains at the same Baud throughout this

Relevant log output

Impact

Functional Limitation – Some features not working as expected, but system usable.

Environment

frdm_mxcn236

Additional Context

No response