On Tue, Jan 21, 2014 at 05:19:13PM -0500, Alan Stern wrote: > On Tue, 21 Jan 2014, Sarah Sharp wrote: > > > Ah, I think I see what's happening. > > > > The xHCI driver is not designed to execute transfers after a stall on a > > non-control endpoint until xhci_endpoint_reset is called and the driver > > fixes up the endpoint ring. That will happen in usb_clear_halt(). > > > > I expect that if an URB is submitted to a stalled non-control endpoint > > before usb_clear_halt is called, the xHCI driver should see EP_HALTED is > > set and refuse to ring the doorbell in that case. Once usb_clear_halt > > calls endpoint_reset, the xHCI driver will clean up the endpoint ring. > > > > The way the code was designed doesn't account for the device driver > > telling the endpoint to halt via a control transfer. The xHC doesn't > > snoop that particular control transfer, so it allows the first URB to be > > submitted. When that transfer stalls, the driver sets EP_HALTED. Then > > the second URB hangs as I expect, because the xHCI driver is waiting for > > usb_clear_halt() to be called. > > > > If it really matters that a driver be able to get an immediate -EPIPE > > response back from a device when the endpoint is halted, I can rip the > > code out of xhci_endpoint_reset() and make the driver manually clean up > > the ring at the time of the stall, like it does for control endpoints > > and babble/transfer/split TX errors. If it doesn't matter, test #13 > > should be changed to only submit one URB and get back an -EPIPE > > response. > > In theory, errors caused by the device sending a STALL should be > handled just like other sorts of errors. After the URB which got the > STALL has been given back, the HCD should automatically restart the > endpoint ring. It should not wait for usb_clear_halt. Mathias, can you look into fixing this? I know you're working on the code to use a configure endpoint command when we can't issue a reset endpoint command, and this change is definitely related. It may even simplify the code to make this change first. Thread, for reference: http://marc.info/?l=linux-usb&m=139025060301432&w=2 Sarah Sharp -- 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
