Ginobili vs Prince, charging foul?

[ysong]

In game 2 Spurs vs Piston, there was a play in which Ginobili tried to penetrate, but run into Prince's front torso hard and knocked him over. But there was not foul call on either player. Ginobili then passed the ball to someone else.

Before the contact, Prince clearly established LGP and then moved into Ginobili's path to draw the contact. It seemed to me there was no illegal move in his part.

If someone noticed this play also, would you help me understand why there was no call on this contact?

Thanks.