@aquiles viza: We don't want the bus interface inside the design if possible. The reason is that we're developing a system that can automatically generate a bus interface to a block, for any bus type that it knows about. You probably need the bus interface for testing, so create a wrapper level for your block and define the bus interface inside that.
I don't think we are at the point of defining the clock frequency for the CPU. So far, I have not seen openlane able to synthesize an SoC-scale design to more than 40MHz, so I would take that as a practical upper limit.