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=-5.3 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,URIBL_BLOCKED,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 D7611C433E0 for ; Thu, 14 May 2020 15:03:02 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id A87F4205CB for ; Thu, 14 May 2020 15:03:02 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=ti.com header.i=@ti.com header.b="IOhrIZWC" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726937AbgENPDB (ORCPT ); Thu, 14 May 2020 11:03:01 -0400 Received: from lelv0142.ext.ti.com ([198.47.23.249]:50886 "EHLO lelv0142.ext.ti.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726179AbgENPDB (ORCPT ); Thu, 14 May 2020 11:03:01 -0400 Received: from lelv0265.itg.ti.com ([10.180.67.224]) by lelv0142.ext.ti.com (8.15.2/8.15.2) with ESMTP id 04EF30Uh033390; Thu, 14 May 2020 10:03:00 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ti.com; s=ti-com-17Q1; t=1589468580; bh=QWbmivzNo6xb5Yvz1JmANWCtfSscs8KNWzHa6puU/9w=; h=Date:From:To:CC:Subject:References:In-Reply-To; b=IOhrIZWCVr+LzmH+JbrHUKqCU8NJV4WBRbieCGImBKyavk0HUxZQy4Uv57+2857h5 R6xUkox5r8XZxHNNoWqx0JjwyLOgxB2BVFWvCkeNIE2/amHaSIcXGTkL8w3uAW95Ee 5lur8ST7ZYwjHxwrt8H6tz7nnwjWwY8t+p36fW7Q= Received: from DFLE105.ent.ti.com (dfle105.ent.ti.com [10.64.6.26]) by lelv0265.itg.ti.com (8.15.2/8.15.2) with ESMTPS id 04EF2xQe062016 (version=TLSv1.2 cipher=AES256-GCM-SHA384 bits=256 verify=FAIL); Thu, 14 May 2020 10:02:59 -0500 Received: from DFLE104.ent.ti.com (10.64.6.25) by DFLE105.ent.ti.com (10.64.6.26) 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 10:02:59 -0500 Received: from fllv0040.itg.ti.com (10.64.41.20) by DFLE104.ent.ti.com (10.64.6.25) 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 10:02:59 -0500 Received: from localhost (ileax41-snat.itg.ti.com [10.172.224.153]) by fllv0040.itg.ti.com (8.15.2/8.15.2) with ESMTP id 04EF2xM2002380; Thu, 14 May 2020 10:02:59 -0500 Date: Thu, 14 May 2020 10:02:59 -0500 From: Bin Liu To: Alan Stern CC: Subject: Re: [PATCH] usb: musb: return -ESHUTDOWN in urb when three-strikes error happened Message-ID: <20200514150259.GB11463@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> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Disposition: inline In-Reply-To: <20200514144053.GC12181@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 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. -Bin.