Mechanical oscillation overloaded

A smooth horizontal disc rotates about the vertical axis $O$ with a constant angular velocity $\omega$ . A thin uniform rod $AB$ of length $l$ performs small oscillations about vertical axis $A$ fixed to the disc at a distance $a$ from the axis of the disc. Find the frequency $f$ of these oscillations.If $a=2 \ , \ \omega =1 \ , \ l=1$ then, find the square of the frequency found.