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 4F598C433DF for ; Thu, 14 May 2020 14:28:12 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 21E0A20727 for ; Thu, 14 May 2020 14:28:12 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=ti.com header.i=@ti.com header.b="i7GkPZgR" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726948AbgENO2L (ORCPT ); Thu, 14 May 2020 10:28:11 -0400 Received: from lelv0142.ext.ti.com ([198.47.23.249]:46556 "EHLO lelv0142.ext.ti.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726240AbgENO2L (ORCPT ); Thu, 14 May 2020 10:28:11 -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 04EES3Qb024335; Thu, 14 May 2020 09:28:03 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ti.com; s=ti-com-17Q1; t=1589466483; bh=JcL1GgFq6aPBT/Uwif3mNiKp0cMxOC6Plm1Gh6vGod8=; h=Date:From:To:CC:Subject:References:In-Reply-To; b=i7GkPZgRqNE4GCaFKCpH+hk8JrnGgEcn5ZXw+tfKfLICVmgkrvlonqhseGcTeTpyq uhsyxtn3l9rPT1sDU0ZZ3f9cPZMmhrQRsNXYI3MZ+waBtBl+6t/C0Zyeg9AGQHOmT8 6gdD8xJwsxRNq94jYEj8REoUxKapZD5hU1a5NIJQ= Received: from DLEE107.ent.ti.com (dlee107.ent.ti.com [157.170.170.37]) by lelv0265.itg.ti.com (8.15.2/8.15.2) with ESMTPS id 04EES3vd014061 (version=TLSv1.2 cipher=AES256-GCM-SHA384 bits=256 verify=FAIL); Thu, 14 May 2020 09:28:03 -0500 Received: from DLEE107.ent.ti.com (157.170.170.37) by DLEE107.ent.ti.com (157.170.170.37) 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 09:28:03 -0500 Received: from fllv0039.itg.ti.com (10.64.41.19) by DLEE107.ent.ti.com (157.170.170.37) 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 09:28:03 -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 04EES3Fv067049; Thu, 14 May 2020 09:28:03 -0500 Date: Thu, 14 May 2020 09:28:03 -0500 From: Bin Liu To: Alan Stern CC: Subject: Re: [PATCH] usb: musb: return -ESHUTDOWN in urb when three-strikes error happened Message-ID: <20200514142803.GA11463@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> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Disposition: inline In-Reply-To: <20200514013205.GA10515@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 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. > the drivers that immediately resubmit an URB after getting a -EPROTO This has been discussed before [1]. And John indicated there are many device drivers do not delay when resubmitting after getting -EPROTO [2], and it is quite bit of work to fix it in all device drivers [3]. So better to solve the issue in HCD. > error. After all, that is the wrong thing to do no matter what sort of > host controller the device is attached to. [1] https://www.spinics.net/lists/linux-usb/msg175292.html [2] https://www.spinics.net/lists/linux-usb/msg176327.html [3] https://www.spinics.net/lists/linux-usb/msg176375.html -Bin.