On Fri, 7 Dec 2012, Sarah Sharp wrote: > On Fri, Dec 07, 2012 at 05:51:55PM -0500, Alan Stern wrote: > > Sarah: > > > > I just tracked down a tricky problem, which appears to be caused by a > > genuine hardware bug. It's hard to believe this has escaped everyone's > > notice for so many years -- maybe my results are wrong. But as far as > > I can tell, they aren't. > > > > Anyway, I don't know what to do about it. Can you forward this message > > to an appropriate person at Intel? > > Sure, I'll try to track the right hardware person down. I'm afraid they > might not be able to help, because they may not remember hardware that is > that old. :-/ For all I know, newer hardware might behave the same way. It's easy enough to test if there's a g-zero gadget at hand, or the equivalent (a high-speed device with a bulk-out endpoint that acts as a sink, accepting all packets). After some thought, I now have an idea for a workaround: add a 1-ms delay whenever a QH is unlinked because of a halt or a dequeue. (Presumably 1 ms is enough time.) Since those are exceptional events, the extra overhead would be acceptable. Still, I would like to check with somebody in a position to confirm or refute this bug. Alan Stern -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
