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From the beginning I gussed that but I had doubts.
You all know that power is a hot issue nowadays. Many techniques for reducing power appeared (Low power techniques, Asynchronous devises, GALS, low power CMOS design etc)
A techniques among these used in new devices composed of multi-submodule is to activate them by letting the clock reach them. This is ensured by a specific controler . Submodules are disabled by the same way when there is no need to them. Obviously, disabling this submudules saves power.
The clock passing controller must be all the time in action because without it system can't run correctly. That's why he is drived by a continuous clock signal or if you like a "free running clock".