The TMR region must be clocked with a single clock, because the triplicated sub-blocks must execute in lockstep.
The TMR SEM clock should be directly provided by the most reliable source possible. For additional details see "Clocking" in Chapter 3 of the Soft Error Mitigation Controller LogiCORE IP Product Guide (PG036) or the UltraScale Architecture Soft Error Mitigation Controller LogiCORE IP Product Guide (PG187).