From mboxrd@z Thu Jan 1 00:00:00 1970 From: Matthew Garrett Subject: Re: [ugly patch] Save .15W-.5W by AHCI powersaving Date: Tue, 26 Feb 2008 16:21:43 +0000 Message-ID: <20080226162142.GA12020@srcf.ucam.org> References: <20080225134558.GA1611@elf.ucw.cz> <47C34081.5090205@rtr.ca> <47C34472.3090706@garzik.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Received: from cavan.codon.org.uk ([78.32.9.130]:39389 "EHLO vavatch.codon.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751012AbYBZQWj (ORCPT ); Tue, 26 Feb 2008 11:22:39 -0500 Content-Disposition: inline In-Reply-To: <47C34472.3090706@garzik.org> Sender: linux-ide-owner@vger.kernel.org List-Id: linux-ide@vger.kernel.org To: Jeff Garzik Cc: Mark Lord , Pavel Machek , kernel list , Linux-pm mailing list , stern@rowland.harvard.edu, linux-ide@vger.kernel.org On Mon, Feb 25, 2008 at 05:42:58PM -0500, Jeff Garzik wrote: > BTW we can also save power by allowing the user to choose to disable > hotplugging support. Then we can power down PHYs that are not in use. > > That requires the addition of some policy controls, because it is > user-specific whether or not to waste power waiting for a plug-in event. For AHCI, if you've enabled link power management then you've already disabled hotplug. We might as well power down unused phys in that case. Note that laptop bays still seem to tend to use platform-specific hotplug notification, even when they're sata - we'll get the hotplug notify for them even if the phy's powered down, so that case also needs to be handled. -- Matthew Garrett | mjg59@srcf.ucam.org