John Mayer on Katy Perry, Learning From the Dead, Embracing Pot

"I have six hours of music coming up tonight," says John Mayer. In a little while, he'll take the stage in Atlanta with Dead & Company – featuring Grateful Dead alum Bob Weir, Mickey Hart and Bill Kreutzmann. After that, Mayer will play a surprise midnight club gig with Dave Chappelle, one of several pop-up shows they've been doing since last spring. "I'm sort of the acoustic DJ," Mayer says. "He'll just be like, 'John, hit me with this or that,' and I'm pretty good at coming up with a