On 12.02.2015 17:18, Alan Stern wrote: > 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? True, those URBs would be left hanging. So if possible, tweaking the Synopsis autosuspend feature would be nicer. If its not possible then I guess a quirk patch like this will do. -Mathias -- 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
