As cjoseph already said, it raly depends on your equipement what is possible.
Most switches support session based authentication which means you ould do dot1x for both devices. Authentication success (or faillure) for 1 device doesn't matter/influence the authentications of other devices on the same port.
So the best would be session based with both devices doing dot1x, although I've often seen dot1x for the PC and mac for the phone.
Most important is the requirement for session based as opposed to port based authentication.