Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756193AbbBLPSW (ORCPT ); Thu, 12 Feb 2015 10:18:22 -0500 Received: from iolanthe.rowland.org ([192.131.102.54]:41983 "HELO iolanthe.rowland.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1755522AbbBLPSU (ORCPT ); Thu, 12 Feb 2015 10:18:20 -0500 Date: Thu, 12 Feb 2015 10:18:19 -0500 (EST) From: Alan Stern X-X-Sender: stern@iolanthe.rowland.org To: Mathias Nyman cc: Sneeker Yeh , Rob Herring , Pawel Moll , Mark Rutland , Ian Campbell , Kumar Gala , Felipe Balbi , Greg Kroah-Hartman , Grant Likely , Huang Rui , Kishon Vijay Abraham I , , , , , Andy Green , Jassi Brar , Sneeker Yeh Subject: Re: [PATCH v3 1/5] xhci: add a quirk for device disconnection errata for Synopsis Designware USB3 core In-Reply-To: <54DCAF88.4010607@intel.com> Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2165 Lines: 46 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-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/