On one dive to 20m I was unable to equalize at 17m. I was in freefall and accidentally went a little deeper then I had anticipated, putting painful pressure on my eardrum. I have to be very careful once I get to negative buoyancy to ensure that I don't fall if I can't equalize. I could prevent this by doing free immersion until I can comfortably equalize at my target.
On another dive, I tried to equalize on my way back up. I am very lucky I did not have a reverse barotrauma from attempting this. You should not voluntarily equalize when you return to the surface. It happens automatically.