From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-5.4 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 0C2A2C433DF for ; Thu, 14 May 2020 17:00:28 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id D23AB20671 for ; Thu, 14 May 2020 17:00:27 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=ti.com header.i=@ti.com header.b="B6k/87ft" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726046AbgENRA1 (ORCPT ); Thu, 14 May 2020 13:00:27 -0400 Received: from fllv0015.ext.ti.com ([198.47.19.141]:55080 "EHLO fllv0015.ext.ti.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725975AbgENRA1 (ORCPT ); Thu, 14 May 2020 13:00:27 -0400 Received: from fllv0035.itg.ti.com ([10.64.41.0]) by fllv0015.ext.ti.com (8.15.2/8.15.2) with ESMTP id 04EH0Ngo059254; Thu, 14 May 2020 12:00:23 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ti.com; s=ti-com-17Q1; t=1589475623; bh=GLRbLklUztjSDMQ1GV6YyicZCwhPBc8ldwcWA+jo/6w=; h=Date:From:To:CC:Subject:References:In-Reply-To; b=B6k/87ftV+WZKaALGCsX5uK1Bh8475WCF0rFMRgpmyWir5sPVWoaCr1ocq/KvhgeU UOpGTwry4tmHULsIhwM/RhbDcTD/zsIz16Mp++5HXeFrfK038WkcgK6wSO9u93Um1P m5CqqeOFFyMk7MTi54GvBvHP5LXXIqYXG9XFSDtQ= Received: from DFLE100.ent.ti.com (dfle100.ent.ti.com [10.64.6.21]) by fllv0035.itg.ti.com (8.15.2/8.15.2) with ESMTP id 04EH0N8D036232; Thu, 14 May 2020 12:00:23 -0500 Received: from DFLE110.ent.ti.com (10.64.6.31) by DFLE100.ent.ti.com (10.64.6.21) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256_P256) id 15.1.1979.3; Thu, 14 May 2020 12:00:23 -0500 Received: from fllv0039.itg.ti.com (10.64.41.19) by DFLE110.ent.ti.com (10.64.6.31) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256_P256) id 15.1.1979.3 via Frontend Transport; Thu, 14 May 2020 12:00:23 -0500 Received: from localhost (ileax41-snat.itg.ti.com [10.172.224.153]) by fllv0039.itg.ti.com (8.15.2/8.15.2) with ESMTP id 04EH0N6P090334; Thu, 14 May 2020 12:00:23 -0500 Date: Thu, 14 May 2020 12:00:23 -0500 From: Bin Liu To: Alan Stern CC: Subject: Re: [PATCH] usb: musb: return -ESHUTDOWN in urb when three-strikes error happened Message-ID: <20200514170023.GD11463@iaqt7> Mail-Followup-To: Bin Liu , Alan Stern , linux-usb@vger.kernel.org References: <20200513213620.21541-1-b-liu@ti.com> <20200514013205.GA10515@rowland.harvard.edu> <20200514142803.GA11463@iaqt7> <20200514144053.GC12181@rowland.harvard.edu> <20200514150259.GB11463@iaqt7> <20200514153731.GC11463@iaqt7> <20200514162604.GA9571@rowland.harvard.edu> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Disposition: inline In-Reply-To: <20200514162604.GA9571@rowland.harvard.edu> User-Agent: Mutt/1.9.4 (2018-02-28) X-EXCLAIMER-MD-CONFIG: e1e8a2fd-e40a-4ac6-ac9b-f7e9cc9ee180 Sender: linux-usb-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-usb@vger.kernel.org On Thu, May 14, 2020 at 12:26:04PM -0400, Alan Stern wrote: > On Thu, May 14, 2020 at 10:37:31AM -0500, Bin Liu wrote: > > On Thu, May 14, 2020 at 10:02:59AM -0500, Bin Liu wrote: > > > On Thu, May 14, 2020 at 10:40:53AM -0400, Alan Stern wrote: > > > > On Thu, May 14, 2020 at 09:28:03AM -0500, Bin Liu wrote: > > > > > On Wed, May 13, 2020 at 09:32:05PM -0400, Alan Stern wrote: > > > > > > On Wed, May 13, 2020 at 04:36:20PM -0500, Bin Liu wrote: > > > > > > > When a USB device attached to a hub got disconnected, MUSB controller > > > > > > > generates RXCSR_RX_ERROR interrupt for the 3-strikes-out error. > > > > > > > > > > > > > > Currently the MUSB host driver returns -EPROTO in current URB, then the > > > > > > > USB device driver could immediately resubmit the URB which causes MUSB > > > > > > > generate RXCSR_RX_ERROR interrupt again. This circle causes interrupt > > > > > > > storm then the hub never got a chance to report the USB device detach. > > > > > > > > > > > > > > To fix the interrupt storm, change the URB return code to -ESHUTDOWN for > > > > > > > MUSB_RXCSR_H_ERROR interrupt, so that the USB device driver will not > > > > > > > immediately resubmit the URB. > > > > > > > > > > > > > > Signed-off-by: Bin Liu > > > > > > > > > > > > Strictly speaking, this is not the right thing to do. It goes against > > > > > > the API described in error-codes.rst. A better approach would be to fix > > > > > > > > > > error-codes.rst says: > > > > > > > > > > -ESHUTDOWN The device or host controller has been > > > > > disabled due to some problem that could not > > > > > be worked around, such as a physical > > > > > disconnect. > > > > > > > > > > So -ESHUTDOWN is applicable in this case - the device is disconnected > > > > > behind a hub. > > > > > > > > Yes, but you don't _know_ that the device was disconnected. All you > > > > know is that there was a 3-strikes error. Other problems can cause such > > > > errors (noise, for example). > > > > > > Yes, I know this. But we don't have a solution then. I cannot add > > > resubmit delay in those ~500 device drivers. > > > > By the way I don't think noise could last long enough to cause 3-strikes > > error. A shortest USB packet is about 3-bytes long, a noise should be > > just a glitch, it won't last at least 3-bytes long to supress the bus > > and 3 times on the exact timing when the host expecting a response > > packet. I cannot think of any other reason which can cause the 3-strikes > > error other than the device is off the bus. > > Heh. I heard from somebody (many years ago) about a setup where one of > his USB devices stopped working whenever he turned on the fluorescent > lights. This could happen, noise comming in from the power supply, cheap power supply and poor board design. > Yes, I agree that noise is pretty uncommon, and the vast majority of > 3-strikes errors are caused by disconnection or device firmware bugs. I wasn't mean noise is uncommon, it is just it won't cause 3-strikes error because the glitch is very short. I have seen many cases that noise causing issues on MUSB due to poor board design especially on those USB modem or WIFI projects. > That's why I didn't NAK this patch. Thanks. > Still, it's worth pointing out that this change abuses the API (perhaps > mentioning it in a comment). And it still would be preferable to fix Okay, I will add those notes in comment in v2. > the drivers in question, impractical though that may be. (I have a hard > time believing there are really 500 of them getting this wrong...) I am not sure about it either, but yeah it is not practical to fix the issue in device drivers. So far I have seen 3 reports of this issue: 1. with FTDI usb-serial adapter, the issue is in the usb serial generic driver; 2. with a modem, the issue is in usb wwan driver as I fixed in the patch I sent yesterday; 2. another modem, before I was able to locate the offending device driver, the guy who reported the issue disappeared, and not responding me. -Bin.