From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759484Ab2HITjK (ORCPT ); Thu, 9 Aug 2012 15:39:10 -0400 Received: from mga11.intel.com ([192.55.52.93]:38039 "EHLO mga11.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1759376Ab2HITjI (ORCPT ); Thu, 9 Aug 2012 15:39:08 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.77,742,1336374000"; d="scan'208";a="195679811" Date: Thu, 9 Aug 2012 12:38:59 -0700 From: Sarah Sharp To: Keng-Yu Lin Cc: Greg Kroah-Hartman , linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] Intel xhci: Only switch the switchable ports Message-ID: <20120809193859.GD14429@xanatos> References: <1344504711-10916-1-git-send-email-kengyu@canonical.com> <20120809142406.GC14429@xanatos> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Aug 10, 2012 at 12:13:19AM +0800, Keng-Yu Lin wrote: > On Thu, Aug 9, 2012 at 10:24 PM, Sarah Sharp > wrote: > > On Thu, Aug 09, 2012 at 05:31:51PM +0800, Keng-Yu Lin wrote: > >> With a previous patch to enable the EHCI/XHCI port switching, it switches > >> all the available ports. > >> > >> The assumption is not correct because the BIOS may expect some ports > >> not switchable by the OS. > > > > Why would the BIOS expect some ports to not be switchable? I know that > > we internally at Intel had discussed some theoretical reasons why it > > might not be good to switch some ports, but when I presented the > > original patch with this same code in it to Linux USB mailing list, both > > Alan and Greg said, "Why not unconditionally switch ports?" I had no > > good examples at the time. > > > > Is this causing issues with some particular BIOS? > > > > Yes, this is causing the internal webcam missing on the USB bus as I > observed on some HM70-based laptops. Does anything show up in dmesg when you turn on CONFIG_USB_XHCI_HCD_DEBUGGING? It would be good to know if it is totally not electrically present, or if there's some sort of xHCI hardware or software issue that's preventing the webcam from being enumerated. > The internal webcam is attached to one port that is controlled by the > xhci host. > But the other ports with the outer plugs work well after booting. I > cannot test the USB port of the internal webcam easily (without > tearing down the laptop :-/). > > I also tried some similar HM77-based models. HM77 has no this issue. > This could be some chipset mystery I am not aware now. Could be. Can you use any SMBIOS information to change the port switchover only for those HM70-based laptops? And is it a particular laptop vendor or all HM70 laptops? As Alan said, I would rather not trust the BIOS to provide the correct port mask. Sarah Sharp