On Sat, 7 Feb 2009, David wrote: > Greetings everyone. > > I have a peculiar problem with USB MIDI timing that appears beginning with > kernel 2.6.24, and still persists in 2.6.28.4. Kernel 2.6.23.17 works fine. > > The symptom is some note events seem to arrive noticeably late. The problem > is most apparent with rapid scales or situations where multiple note events > are supposed to be played at once (chords). > > The MIDI interface dongle I am using is only a full speed device. > > The problem is _not_ present when connected directly to the root hub (the > MIDI dongle binds to the OHCI driver), and it is not present with > ehci_hcd unloaded or unbind'ed from the EHCI interface handling the bus > (forcing everything to use ohci), even when using external hubs. > > The problem _is_ present when the MIDI dongle is connected to any > external USB 2.0 hub and EHCI is in use. I have reproduced on 2 different > hosts with two different EHCI chipsets (NVIDIA and ICH9) and about 4 > different hubs. No EHCI setup with kernel >=2.6.24 works right. Not > knowing anything else, I would suspect the problem has something to do with > scheduling at the hub's TT. For problems like this, git -bisect may be the best approach. 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
