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=-3.8 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS autolearn=no 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 33F86C282DD for ; Thu, 9 Jan 2020 15:46:34 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id EBCF520721 for ; Thu, 9 Jan 2020 15:46:33 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1578584794; bh=sYZtkBBoBfP32KtLm6hChjUFQPnxZwOrEJFm48tRQt4=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=VEfjq33bICxAGKXr1wIxE7xCc4Vi9+o8v+yIAmWRQzyT3meJ3NViWb4Fnpby2SX2Q D0LFQEBFEXRtClNmQmKgM7BbTvJVugZKd5TG5vrSEY4DzUZ/giXp+FQrVFMnBEq91W cIAXd3+E+h4frsnhuN+gwxeKBD/mRZf6+3BAP254= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732530AbgAIPqd (ORCPT ); Thu, 9 Jan 2020 10:46:33 -0500 Received: from mail.kernel.org ([198.145.29.99]:43128 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728293AbgAIPqd (ORCPT ); Thu, 9 Jan 2020 10:46:33 -0500 Received: from localhost (83-86-89-107.cable.dynamic.v4.ziggo.nl [83.86.89.107]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 82F592067D; Thu, 9 Jan 2020 15:46:32 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1578584793; bh=sYZtkBBoBfP32KtLm6hChjUFQPnxZwOrEJFm48tRQt4=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=0txmMl51Zfkw9KnkMykWpjpKN003D7ncgDrG5d2gBOiZwocdzCeMnKPuY/7yldFnO EV/mV0jlFSxuAR6vHQF/TnNYUbfxLd9gk6suVtQ4QvSTQVZKPgEkRNq85LHXBWL6z6 ATjFb8943t26hTp0CN4vRXA57N9ijGU2A+DLjNpI= Date: Thu, 9 Jan 2020 16:46:30 +0100 From: Greg KH To: Keiya Nobuta Cc: linux-usb@vger.kernel.org Subject: Re: [PATCH] usb: core: hub: Improved device recognition on remote wakeup Message-ID: <20200109154630.GA549548@kroah.com> References: <20200109051448.28150-1-nobuta.keiya@fujitsu.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200109051448.28150-1-nobuta.keiya@fujitsu.com> Sender: linux-usb-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-usb@vger.kernel.org On Thu, Jan 09, 2020 at 02:14:48PM +0900, Keiya Nobuta wrote: > If hub_activate() is called before D+ has stabilized after remote > wakeup, the following situation might occur: > > __ ___________________ > / \ / > D+ __/ \__/ > > Hub _______________________________ > | ^ ^ ^ > | | | | > Host _____v__|___|___________|______ > | | | | > | | | \-- Interrupt Transfer (*3) > | | \-- ClearPortFeature (*2) > | \-- GetPortStatus (*1) > \-- Host detects remote wakeup > > - D+ goes high, Host starts running by remote wakeup > - D+ is not stable, goes low > - Host requests GetPortStatus at (*1) and gets the following hub status: > - Current Connect Status bit is 0 > - Connect Status Change bit is 1 > - D+ stabilizes, goes high > - Host requests ClearPortFeature and thus Connect Status Change bit is > cleared at (*2) > - After waiting 100 ms, Host starts the Interrupt Transfer at (*3) > - Since the Connect Status Change bit is 0, Hub returns NAK. > > In this case, port_event() is not called in hub_event() and Host cannot > recognize device. To solve this issue, flag change_bits even if only > Connect Status Change bit is 1 when got in the first GetPortStatus. > > This issue occurs rarely because it only if D+ changes during a very > short time between GetPortStatus and ClearPortFeature. However, it is > fatal if it occurs in embedded system. > > Signed-off-by: Keiya Nobuta > --- > drivers/usb/core/hub.c | 1 + > 1 file changed, 1 insertion(+) Is this something that should go into 5.5-final and the stable trees? Or is it ok for 5.6-rc1? thanks, greg k-h