After Robert finishes arguing with his squires before the tourney, what does Robert reveal to Eddard about Joffrey and Cersei?

After the disagreement with his squires, Robert tells Eddard he thinks that Joffrey lied about his sword fight with Arya, and that he is unhappy with Joffrey's behavior. Robert also tells Eddard that he is unhappy in his marriage and that he only married Cersei to produce an heir. Robert says he is thinking of leaving Cersei to marry the sister of another lord.