Digital timing recovery for servo operations during start-up mode

A storage device, comprising:

• a rotating magnetic storage medium having at least one servo wedge that includes a servo preamble written at a known preamble frequency;
• and
• a read channel controller configured to recover a servo write frequency for reading servo wedge data from the rotating magnetic storage medium, the read channel controller comprising:
• circuitry configured to analyze samples of data read from the rotating magnetic storage medium to identify samples in which energy at the known preamble frequency exceeds a predetermined threshold;
• circuitry configured to declare location of the servo preamble based on the identification of the samples in which energy at the known preamble frequency exceeds the predetermined threshold;
• circuitry configured to derive a phase angle from the samples in which the energy at the known preamble frequency exceeds the predetermined threshold;
• circuitry configured to update an accumulated phase angle using the derived phase angle;
• and
• circuitry configured to use the derived phase angle to start a timing recovery loop to recover the servo write frequency.