Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755505AbYHMOqv (ORCPT ); Wed, 13 Aug 2008 10:46:51 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751449AbYHMOqm (ORCPT ); Wed, 13 Aug 2008 10:46:42 -0400 Received: from mx2.suse.de ([195.135.220.15]:55676 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750973AbYHMOqm (ORCPT ); Wed, 13 Aug 2008 10:46:42 -0400 From: Oliver Neukum Organization: Novell To: Alan Stern Subject: Re: Power management for SCSI Date: Wed, 13 Aug 2008 16:47:42 +0200 User-Agent: KMail/1.9.9 Cc: Pavel Machek , kernel list , "Linux-pm mailing list" , James.Bottomley@hansenpartnership.com, teheo@novell.com References: In-Reply-To: MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Content-Disposition: inline Message-Id: <200808131647.43989.oneukum@suse.de> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1480 Lines: 36 Am Mittwoch 13 August 2008 16:31:03 schrieb Alan Stern: > On Wed, 13 Aug 2008, Pavel Machek wrote: > > > From: Alan Stern > > > > Add support for autosuspend/autoresume. Lowlevel driver can use it to > > spin the disk down and power down its SATA link, to turn off the USB > > interface, etc. > > > > Spinning down the disk is useful - saves ~0.5W here. Powering down > > SATA controller is even better -- should save ~1W. > > > > Now, I guess the patch will need to be split to small pieces for > > merge... I tried to rearrange it so that the documentation and hooks > > go before stuff that needs the hooks, and before Kconfig enabler. If > > it looks reasonably good, I'll split it into smaller pieces. > > James had a number of objections to my original patch; you can read > them here: > > https://lists.linux-foundation.org/pipermail/linux-pm/2008-March/016849.html Very well. I see a basic problem here. For USB it is necessary that child devices be suspended before anything higher up in the tree is suspended. SATA seems to be able to power down a link while the device is not suspended. In fact in true SCSI busses can be shared. So are we using the correct approach? Regards Oliver -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/