From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1760603AbXHTR31 (ORCPT ); Mon, 20 Aug 2007 13:29:27 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1750869AbXHTR3T (ORCPT ); Mon, 20 Aug 2007 13:29:19 -0400 Received: from gprs189-60.eurotel.cz ([160.218.189.60]:2612 "EHLO spitz.ucw.cz" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1750720AbXHTR3T (ORCPT ); Mon, 20 Aug 2007 13:29:19 -0400 Date: Mon, 20 Aug 2007 17:29:07 +0000 From: Pavel Machek To: Oliver Neukum Cc: Jean Delvare , "Rafael J. Wysocki" , LKML Subject: Re: CONFIG_SUSPEND and power consumption Message-ID: <20070820172907.GC3975@ucw.cz> References: <20070819153259.2c96b904@hyperion.delvare> <200708192242.43819.rjw@sisk.pl> <20070820120258.7d090cc4@hyperion.delvare> <200708201211.34698.oliver@neukum.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <200708201211.34698.oliver@neukum.org> User-Agent: Mutt/1.5.9i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Hi! > > If I rmmod "ehci-hcd" then the power consumption is back to 69 W. This > > confirms that this is really USB-related. I have to admit that I did > > not expect an external drive to eat that much power from the system, > > especially when not used. I am told that VIA chips are notoriously bad > > at this kind of things. I'll try the same external drive on an Intel > > system later today. > > > > The last mystery remaining is how USB "activity" can cause my CPU to > > heat. I would expect the south bridge to heat, not the CPU. > > USB, or strictly speaking EHCI, OHCI and UHCI, use DMA. To allow > that the cache coherency logic has to be active. Therefore your CPU > cannot go to C3. Therefore it draws more power. The problem we are > facing in USB is that to get great savings, our coverage has to be perfect. > One device that cannot be autosuspended and we lose most savings. Ok.. but CONFIG_USB_SUSPEND should not really have anything to do with CONFIG_SUSPEND (= s2ram). Perhaps it should depend on CONFIG_PM instead? Pavel -- (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html