For details, take a look at <file:Documentation/cpu-freq/>.
If you don't have such processor, say N
+config CBE_CPUFREQ_PMI
+ tristate "CBE frequency scaling using PMI interface"
+ depends on CBE_CPUFREQ && PPC_PMI && EXPERIMENTAL
+ default n
+ help
+ Select this, if you want to use the PMI interface
+ to switch frequencies. Using PMI, the
+ processor will not only be able to run at lower speed,
+ but also at lower core voltage.
+
endmenu