Downclock when idle

[wonderiuy]

Hi all, long time crawler but first message here.

My question is: are these commands supported in config.txt?
arm_freq_min
core_freq_min
sdram_freq_min
over_voltage_min

They should work only on overclocked RPI and are used to specify the frequency of clocks when system go idle or with low cpu load. I've added them to config.txt but they doesn't seem to work (or it seems that they are never triggered).

I've added also the line
force_turbo=0
and disabled initial_turbo
but with no success.

All commands can be found here: http://elinux.org/RPi_config.txt#Overclocking_options
Since i'm not a Linux expert, do you have any suggestions?
Thank you in advance