A hard disk drive or other storage device comprises a storage medium, a read head configured to read data from the storage medium, and control circuitry coupled to the read head and configured to process data received from the read head. The control circuitry comprises read channel circuitry that includes a low-density parity check decoder or other type of decoder. Power management circuitry associated with the read channel circuitry is configured to detect a power control condition of the read channel circuitry and to control insertion of idle clock cycles in a clock signal supplied to the decoder responsive to the detected power control condition. For example, the read channel circuitry may comprise a clock generator configured to gate the clock signal responsive to a control signal from the power management circuitry.