A system and method for managing idleness of functional units in an IC is disclosed. An IC includes a subsystem having a number of functional units and an idle aggregation unit. When a particular functional unit determines that it is idle, it may assert an idle indication to the idle aggregation unit. When the respective idle indications are concurrently asserted for all of the functional units, the idle aggregation unit may assert and provide respective idle request signals to each of the functional units. Responsive to receiving an idle request unit, a given functional unit may provide an acknowledgement signal to the idle aggregation unit if no transactions are incoming. If all functional units have concurrently asserted their respective acknowledgement signals, the idle aggregation unit may provide an indication of the same to a clock gating unit, which may then gate the clock signal(s) received by the functional units.