A downhole tool has a housing, a piston, and a seat and is for use with a deployed plug or ball and applied fluid pressure. The housing defines a bore, and the piston is disposed in the bore of the housing and is biased to move from a first position to a second position. The seat is also disposed in the bore of the housing and is operably connected to the piston. The seat rotates from a first orientation for engaging the deployed plug to a second orientation for passing the deployed plug in response to movement of the piston from the first position near the seat to the second position away from the seat.