From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Rafael J. Wysocki" Subject: Re: USB suspend/resume in linux Date: Fri, 13 Oct 2006 13:28:40 +0200 Message-ID: <200610131328.40857.rjw@sisk.pl> References: <0FB24CC078F78248B19595A43F00E01FD92D24@fmsmsx413.amr.corp.intel.com> <1160728740.2096.243.camel@queen.suse.de> Mime-Version: 1.0 Content-Type: text/plain; charset="iso-8859-15" Content-Transfer-Encoding: 7bit Return-path: Received: from ogre.sisk.pl ([217.79.144.158]:29120 "EHLO ogre.sisk.pl") by vger.kernel.org with ESMTP id S1751329AbWJML24 (ORCPT ); Fri, 13 Oct 2006 07:28:56 -0400 In-Reply-To: <1160728740.2096.243.camel@queen.suse.de> Content-Disposition: inline Sender: linux-acpi-owner@vger.kernel.org List-Id: linux-acpi@vger.kernel.org To: trenn@suse.de Cc: "Kaburlasos, Nikos" , linux-acpi@vger.kernel.org, Alan Stern On Friday, 13 October 2006 10:39, Thomas Renninger wrote: > On Thu, 2006-10-12 at 22:54 -0700, Kaburlasos, Nikos wrote: > > Does anyone know whether the linux USB drivers support the suspend > > feature on idle USB ports (i.e. the port has been idle for sometime and > > so the driver transitions it in to a low-power 'suspend' state) while > > the system is active and in S0 state? As far as I know, Windows don't > > support that, I was wondering if linux does. > > > > Please note, I have no background on linux or in OS programming (I am a > > hardware guy), so please be gentle with the level of technical detail in > > your response :-) > > AFAIK linux is not doing that. > Therefore the ohci (also uhci?) drivers need to poll the ports quite > often even there is no device attached. This makes C-states less > efficient (what should save more power than the suspended USB ports). I > thought Windows is doing that, I at least heard Mac OS is doing it like > that, but I don't know for sure. > The proper solution to avoid polling should be to suspend idle ports, > stop polling and wait for some kind of resume/attach event, but AFAIK > nobody really works on that. Would be nice if someone gives this a > try... Alan Stern has been working on USB autosuspend for quite some time and there are some patches in -mm and in the recent mainline, AFAICT. Greetings, Rafael -- You never change things by fighting the existing reality. R. Buckminster Fuller