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 65D6DC433E0 for ; Thu, 14 May 2020 15:37:44 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 436CD20748 for ; Thu, 14 May 2020 15:37:44 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=ti.com header.i=@ti.com header.b="CWBh8ls8" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726140AbgENPhn (ORCPT ); Thu, 14 May 2020 11:37:43 -0400 Received: from fllv0015.ext.ti.com ([198.47.19.141]:46200 "EHLO fllv0015.ext.ti.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726056AbgENPhn (ORCPT ); Thu, 14 May 2020 11:37:43 -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 04EFbWWG038791; Thu, 14 May 2020 10:37:32 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ti.com; s=ti-com-17Q1; t=1589470652; bh=9dmxYR59N72XLEGvzkJqaRIEeYqAerbSrGl6ao8cXvA=; h=Date:From:To:Subject:References:In-Reply-To; b=CWBh8ls8NgW5E0YGkl0+CvtqWd9zZO/zhDv8VzUVtwGA9ClWoT31N256QtkuiwoYg e40AS2ow3om3TMwsB3CvgL+y0QaTrXb5lfFgojM2MyEjw9xu6N0h8teh3Bdhkd2bxV c3Zpf5yJC8E4IL9DBbVn4hXNJERh3YFfRa1I0eec= Received: from DLEE107.ent.ti.com (dlee107.ent.ti.com [157.170.170.37]) by fllv0035.itg.ti.com (8.15.2/8.15.2) with ESMTP id 04EFbWK0052374; Thu, 14 May 2020 10:37:32 -0500 Received: from DLEE105.ent.ti.com (157.170.170.35) 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 10:37:31 -0500 Received: from lelv0326.itg.ti.com (10.180.67.84) by DLEE105.ent.ti.com (157.170.170.35) 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 10:37:31 -0500 Received: from localhost (ileax41-snat.itg.ti.com [10.172.224.153]) by lelv0326.itg.ti.com (8.15.2/8.15.2) with ESMTP id 04EFbVXE094744; Thu, 14 May 2020 10:37:31 -0500 Date: Thu, 14 May 2020 10:37:31 -0500 From: Bin Liu To: Alan Stern , Subject: Re: [PATCH] usb: musb: return -ESHUTDOWN in urb when three-strikes error happened Message-ID: <20200514153731.GC11463@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> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Disposition: inline In-Reply-To: <20200514150259.GB11463@iaqt7> 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 10:02:59AM -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. -Bin.