The purpose of a cpuidle governor is to decide which idle state a CPU
should go into when it has no useful work to do; the cpuidle driver
then actually puts the CPU
into that state. But, at the 2020 Power Management and Scheduling
in the Linux Kernel summit (OSPM), Abhishek Goel presented a new
cpuidle driver that doesn’t actually change the processor’s power state at all.
Such a driver will clearly save no power, but it can be quite useful as a
tool for evaluating and debugging cpuidle policies.

Source: LWN.net – [$] The pseudo cpuidle driver