Patti Smith used to plays songs like “Piss Factory” at dingy clubs like the Rat. Not so much anymore. At 69, Smith is an elder stateswoman of rock. She still performs, but it often involves reading from her beautiful, best-selling books, “Just Kids,” which was published in 2010, and last year’s “M Train.” Tuesday, Smith talked about the two memoirs in a sitdown with South Boston scribe Michael Patrick MacDonald (above. with Smith) at the Berklee Performance Center. “She’s funny. As a kid, she wanted to be like Johnny Carson, so there were a lot of laughs,” MacDonald, author of “All Souls” and “Easter Rising,” said afterward. But Smith was also serious — seriously upset — about the amount of money that’s spent on elections in the US at a time when millions of children are hungry and schools are failing. Of course, the godmother of punk wasn’t going to leave the stage without playing a song for her fans, many of whom have been paying attention to Smith since her debut LP, “Horses,” in 1975. So Patti summoned her bandmate Tony Shanahan to the stage and treated the crowd to acoustic versions of “Wing,” Lou Reed’s “Perfect Day,” her biggest hit “Because the Night,” and, finally, “People Have the Power.”