On Thu, 12 Feb 2015, Mathias Nyman wrote: > On 25.01.2015 10:13, Sneeker Yeh wrote: > > This issue is defined by a three-way race at disconnect, between > > 1) Class driver interrupt endpoint resheduling attempts if the ISR gave an ep > > error event due to device detach (it would try 3 times) > > 2) Disconnect interrupt on PORTSC_CSC, which is cleared by hub thread > > asynchronously > > 3) The hardware IP was configured in silicon with > > - DWC_USB3_SUSPEND_ON_DISCONNECT_EN=1 > > - Synopsys IP version is < 3.00a > > The IP will auto-suspend itself on device detach with some phy-specific interval > > after CSC is cleared by 2) > > > > If 2) and 3) complete before 1), the interrupts it expects will not be generated > > by the autosuspended IP, leading to a deadlock. Even later disconnection > > procedure would detect that corresponding urb is still in-progress and issue a > > ep stop command, auto-suspended IP still won't respond to that command. If the Synopsys IP provides a way to do it, it would be better to turn off the autosuspend feature entirely. Doesn't autosuspend violate the xHCI specification? > So did I understand correctly that the class driver submits a new urb which > is enqueued by xhci_urb_enqueue() before the hub thread notices the device is disconnected. > Then hub thread clears CSC bit, controller suspends and the new urb is never given back? > > Doesn't the CSC bit and PORT_CONNECT bit show the device is disconnected when we enter > xhci_enqueue_urb(), even it the hub thread doesn't know this yet? What if the device disconnects _after_ the new URB is enqueued? > Would it make sense to check those bits in xhci_enqueue_urb, and just return error > in the xhci_urb_enqueue() if device is not connected? Then there wouldn't be a need for any quirk > at all. That wouldn't help URBs that were already enqueued when the disconnect occurred. Alan Stern -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
