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=-7.5 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,USER_AGENT_SANE_1 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 79239C433E6 for ; Thu, 4 Mar 2021 01:37:01 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 3FF7565031 for ; Thu, 4 Mar 2021 01:37:01 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231744AbhCDBgi (ORCPT ); Wed, 3 Mar 2021 20:36:38 -0500 Received: from mail.kernel.org ([198.145.29.99]:59634 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231683AbhCDBgf (ORCPT ); Wed, 3 Mar 2021 20:36:35 -0500 Received: by mail.kernel.org (Postfix) with ESMTPSA id 717F56523D; Thu, 4 Mar 2021 01:35:52 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1614821753; bh=Qe7zGUitWIYRrO9+yOOXaqCaFvUR2e3wtBb+ql0NqIA=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=Y7w5u5sgdSYnaZk7ektFug+FNzuWFx+BfLgvydnYyBsjboq9UDNoTmaHGrnrXDXS0 VxmQtz5yAf5FXliFzO5wCmNq8zsi1LYLr0VZRLB1whaigliLnrdoj0kHJOOLK6WX+K 52gbShNnbjmASVJYsXrSUhyGm8wWlhzXyCTHIcNtS4mk18lqIbvi4OWhoSL0q+xup2 1yO6hBOwA7u7lMz3Er3MamRdtIs0l9IUJBASRYX5ZpuavDYv5E7posggNyYfgbibaa sD9sBXSlnA9W5OJt7JFFpSnQFS3BNpXeBpNuP1txZsKOWGshA0N/NceUjL4E3997Uu nHekpx+ft246Q== Date: Thu, 4 Mar 2021 09:35:49 +0800 From: Peter Chen To: liulongfang Cc: Greg KH , mathias.nyman@intel.com, linux-usb@vger.kernel.org, yisen.zhuang@huawei.com, linux-kernel@vger.kernel.org Subject: Re: [RFC PATCH] USB:XHCI:Modify XHCI driver for USB2.0 controller Message-ID: <20210304013548.GA16596@nchen> References: <1614327697-1021-1-git-send-email-liulongfang@huawei.com> <87cc8b54-f530-cce0-3ea2-f879436ff5f7@huawei.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <87cc8b54-f530-cce0-3ea2-f879436ff5f7@huawei.com> User-Agent: Mutt/1.9.4 (2018-02-28) Precedence: bulk List-ID: X-Mailing-List: linux-usb@vger.kernel.org On 21-02-27 11:31:00, liulongfang wrote: > On 2021/2/26 16:38, Greg KH wrote: > > On Fri, Feb 26, 2021 at 04:21:37PM +0800, Longfang Liu wrote: > >> Our current XHCI hardware controller has been customized to only > >> support USB 2.0 ports. > > > > That sounds like a spec violation, right? Why do you want to do this? > > > > greg k-h > > . > > > I hope to support a USB2.0-only mode on the XHCI controller > through software configuration. > Thanks. If your hardware has disabled USB3 logic, when the USB3 device is plugged, since there are no RX signal on the bus, the device will not enable USB3 logic, and only USB2 signals will be on the bus, there are only USB devices on USB2 roothub later. So, any issues you have met? -- Thanks, Peter Chen