On Monday 20 April 2009, Dan Streetman wrote: > So David, Greg, can you use that technical description, and an > end-user description of: > > If you are having problems with devices or hub ports resetting when > you start using a USB audio or video (Isochronous) device, this patch > may help. Maybe "resetting, or failed Interrupt transfers, when ..." ? That would be an improvement, yes. Probably enough to alert the folks who would need to care. - Dave > On Mon, Apr 20, 2009 at 10:52 AM, Alan Stern <stern@xxxxxxxxxxxxxxxxxxx> wrote: > > On Mon, 20 Apr 2009, Dan Streetman wrote: > > > >> Well, the theoretical problem is that the bug could delay a transfer > >> long enough that it doesn't finish in time for the TT to transfer the > >> data back in the last scheduled CSPLIT for the transfer. I suspect > >> this would look like, when a user starts using an isoc device like USB > >> audio or video, another device that was already connected stops > >> working. I have not seen this problem myself. > >> > >> The failure report from James is that when he starts using a USB audio > >> device, his mouse gets port reset. James, did you see any "-110" or > >> "timeout" errors before the port reset? I would expect timeout > >> errors, not a port reset (I think the EHCI driver handles all the > >> CSPLITs failing as a timeout error, right?). There may be code that > >> does a port reset on too many timeout errors to try to recover a > >> device. > > > > Yes, the usbhid driver does that. > > > > You can describe the symptom this way: > > > > Without this patch, the driver won't check that the last fully-occupied > > uframe for a new split transaction was vacant beforehand. This can > > lead to a situation in which the first 188 bytes of a 192-byte > > isochronous transfer are scheduled in the same uframe as an existing > > interrupt transfer. The resulting schedule looks like this: > > > > uframe 0: 188-byte isoc-OUT SSPLIT, 8-byte int-IN SSPLIT > > uframe 1: 4-byte isoc-OUT SSPLIT > > > > The SSPLITs are intermingled, causing an error in the downstream hub's > > TT. > > > > 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
