From mboxrd@z Thu Jan 1 00:00:00 1970 From: Thomas Renninger Subject: Re: USB suspend/resume in linux Date: Fri, 13 Oct 2006 10:39:00 +0200 Message-ID: <1160728740.2096.243.camel@queen.suse.de> References: <0FB24CC078F78248B19595A43F00E01FD92D24@fmsmsx413.amr.corp.intel.com> Reply-To: trenn@suse.de Mime-Version: 1.0 Content-Type: text/plain Content-Transfer-Encoding: 7bit Return-path: Received: from mail.suse.de ([195.135.220.2]:10369 "EHLO mx1.suse.de") by vger.kernel.org with ESMTP id S1750832AbWJMI2f (ORCPT ); Fri, 13 Oct 2006 04:28:35 -0400 In-Reply-To: <0FB24CC078F78248B19595A43F00E01FD92D24@fmsmsx413.amr.corp.intel.com> Sender: linux-acpi-owner@vger.kernel.org List-Id: linux-acpi@vger.kernel.org To: "Kaburlasos, Nikos" Cc: linux-acpi@vger.kernel.org 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... Thomas