CONFIG_CPU_VOLTAGE is not available for thedefaultarchitecture x86.
Result is shown for architecture blackfin
default or selected kernelversion does not have config value CONFIG_CPU_VOLTAGE.
Result is shown for kernelversion 6.7-rc3

CPU Voltage scaling

modulename: dpmc.ko


Linux Kernel Configuration
└─>CPU Frequency scaling
└─>CPU Voltage scaling
In linux kernel since version 2.6.26 (release Date: 2008-07-13)  
Say Y here if you want CPU voltage scaling according to the CPU frequency.
This option violates the PLL BYPASS recommendation in the Blackfin Processor
manuals. There is a theoretical risk that during VDDINT transitions
the PLL may unlock.

source code: