quantum mechanics - Can I apply $E=hf$ to a particle having mass?

I am reading concepts of modern physics (by Arthur Beiser) where he calculates the de Broglie wave velocity. For that he uses the relation $v = fλ$ where $v$, $f$, and $λ$ are velocity (de Broglie wave), frequency, and wavelength, respectively. Now for the wavelength, he uses the de Broglie wavelength and for frequency he writes:

$E = \gamma mc^2 =hf$.

But can I apply $E=hf$ to a particle having mass? I thought it applied only to photons?

Answer

It works fine. The reason you usually see it applied to photons is because people already believe light is waves when they start learning QM, so they accept it has a frequency.