If I were you I would meet with HR. At my Company, I've talked to my Senior Director, Site Head, and the head of HR. My direct supervisor doesn't know, and doesn't really need to since I don't think my work is severely affected by my disorder.

However if your work is being affected, you should definitely go to HR. If necessary they can have or facilitate a meeting with your supervisor. But I wouldn't go to your supervisor as the first step. There are various rules wrapped up in the ADA that HR should be well-versed in. If you're asking for "reasonable accommodations," they have to comply. Be careful with that though, because you can't expect too much. There are people who think that's a free pass to not work and still pull a salary, but that's not the spirit of the law.

Good luck, whatever you decide.