Coach Jimbo Fisher announced Johnson's suspension Thursday for a violation of athletic department policy. The school released no details on what led to the suspension.
Other media outlets are reporting an altercation involving Johnson on Wednesday night at a Tallahassee bar.
A call placed to the Tallahassee Police Department by The Associated Press wasn't immediately returned.
Johnson led Jacksonville's First Coast High School to a 12-1 season last year and the Class 8A regional final. He graduated and enrolled early at Florida State, where he played in the Seminoles' spring game.