In order for the OS to manage the processor power states the BIOS CPU Power Management Profile needs to be set to “Performance per Watt(OS)” which is the recommended BIOS settings for all Dell EMC PowerEdge systems when using Red Hat Enterprise Linux.
Dell EMC PowerEdge systems by default have the CPU Power Management Profile set to ”Performance per Watt(DAPC)”, where DAPC stand for Dell Active Power Control. The DAPC mode only allows the BIOS to manage the processor power states.
If CPU Scaling is not working on your Dell EMC PowerEdge system please verify the BIOS settings are as recommended. The settings can be found at System BIOS-> System Profile Settings -> System Profile.
Please refer to Dell EMC published BIOS Setup User Guides for your specific system to determine the how to configure the recommended settings.