Alan Stern wrote: > On Thu, 14 Jul 2011, Sebastian Andrzej Siewior wrote: >> Is it possible that since you defer the unlinking you don't interrupt >> the internal HUB in the middle of whatever it is doing? Maybe the way >> the transfers are unlinked is something that confuses the internal hub. > > Ah -- that was the clue I didn't notice before. > > When an URB is unlinked, and it is for a full-speed/low-speed device > attached via a high-speed hub, it is necessary to send a > Clear-TT-Buffer request to the hub. The usbmon log did not show any > such requests being sent. Without them, the TT buffers in the hub > never drain and it becomes impossible to send any more control or bulk > messages to that device (or to any other device sharing the same TT). > > Any high-speed host controller driver has to call > usb_hub_clear_tt_buffer() when a bulk or control URB going through a TT > is unlinked or fails for any reason other than -EPIPE or -EREMOTEIO. > Also, the driver must define a .clear_tt_buffer_complete callback in > its hc_driver structure, and it must not send any transactions to the > URB's endpoint until the callback tells it the TT buffer has been > cleared. > > This is all explained in section 11.17 of the USB-2 spec. See > especially 11.17.5 for a discussion of Clear-TT-Buffer. > Yep, that seems to do the trick! I need to clean up my code a bit but then I'll get back with some patches. (Wow, this is the first time since I started working on the isp1760 - in, what was it, september? - that I have no known problems with it! *woohoo!* :) While greping drivers/usb/host/ I noticed that the only other driver that call usb_hub_clear_tt_buffer() is the ehci driver (drivers/usb/host/ehci-q.c). Are all the other supported host controllers <= USB1.1 controllers? -- Arvid Brodin Enea Services Stockholm AB -- 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
