The notion of free will does not require either dualism where mental activity controls physical effects nor top-down causality. That is, there exist descriptions of free will that could be called "causal indeterminist or event-causal libertarian" views of free will as Robert Kane describes his own position.
The overview to Mark Balaguer's Free Will as an Open Scientific Problem describes a similar position to Kane's:
...contrary to the traditional wisdom, the libertarian question
reduces to a question about indeterminacy—in particular, to a
straightforward empirical question about whether certain neural events
in our heads are causally undetermined in a certain specific way; in
other words, Balaguer argues that the right kind of indeterminacy
would bring with it all of the other requirements for libertarian free
That indeterminacy is present at the quantum level implies that it cannot be ruled out at the human level and so the problem of free will is open and from a physicalist perspective is a scientific problem.
Mark Balaguer, Free Will, MIT Press, 2014.
Mark Balaguer, Free Will as an Open Scientific Problem, MIT Press, 2012
Robert Kane, "Free Will: New Foundations for an Ancient Problem", Proceedings of the British Academy: 48 (1962), pp. 1-25, (Reprinted 2009 in Hackett Readings in Philosophy, Free Will)