RK3576 CPU OPP Needs investigating

As reported on the upstream mailing list, there appear to be some issues with the RK3576 CPU OPPs.

There is indeed something weird going on. I've tried running sbc-bench [1], and even though I observe dynamically varying CPU frequencies after boot with schedutil governor, once sbc-bench switches the governor to "performance" and goes through the OPPs in descending frequency order, the CPUs seem to get stuck at the last applied low frequency. Even after max frequency gets reverted from 408 MHz to something higher, even after I switch the governor to something else - no matter what. Only a reboot gets the higher frequencies 'unstuck' for me.

These are all observed at around 55C SoC temperature, so throttling is not an issue. Regulators are stuck at 950000 uV - way above 700000 uV that the 408 MHz OPP requires (and power readings seem to match: I'm getting about 2.3W consumption at 408 MHz in idle vs. normal idle reading of 1.4W at around 1 GHz).

As noted in my reply, this may once again be either clock ID confusion or SCMI deviating from what Linux thinks the clock frequency is by way of e.g. PVTPLL.

This needs some investigation, including a solid way to reproduce the behavior, and then a fix.