The disclosure relates to a system including a set of subsystems sharing a voltage rail. The system includes a power controller configured to send messages, such as interrupts, to the subsystems concerning a change of state of a supply voltage on the voltage rail. Such messages may have been sent in response to requests and messages from the subsystems, respectively. In response to the messages, the subsystems may send requests to the power controller for different dynamic clock voltage scaling (DCVS) levels, respectively. In response to such requests, the power controller may set the supply voltage and frequencies of clock signals for the requesting subsystems, respectively.