From mboxrd@z Thu Jan 1 00:00:00 1970 From: Arjan van de Ven Subject: Re: [patch 0/3] AHCI Link Power Management Date: Mon, 11 Jun 2007 20:12:40 -0700 Message-ID: <466E0F28.3040701@linux.intel.com> References: <20070611114600.7fca1c24.kristen.c.accardi@intel.com> <466DFDB5.9030901@gmail.com> <466E0642.5020506@linux.intel.com> <466E0F30.3000700@garzik.org> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <466E0F30.3000700@garzik.org> Sender: linux-kernel-owner@vger.kernel.org To: Jeff Garzik Cc: Tejun Heo , Kristen Carlson Accardi , james.bottomley@steeleye.com, linux-ide@vger.kernel.org, linux-scsi@vger.kernel.org, linux-kernel@vger.kernel.org List-Id: linux-scsi@vger.kernel.org Jeff Garzik wrote: > Arjan van de Ven wrote: >> Tejun Heo wrote: >>> Kristen Carlson Accardi wrote: >>>> Hi, >>>> This series of patches enables Aggressive Link Power Management for >>>> AHCI devices, as documented in the AHCI spec. On my laptop (a >>>> Lenovo X60), this >>>> saves me a full watt of power. On other systems, reported power >>>> savings >>>> range from .5-1.5 Watts. It has been tested by the kind folks at >>>> #powertop >>>> with similar results. Please give it a try and let me know what you >>>> think. >>> >>> I'm not sure about this. We need better PM framework to support >>> powersaving in other controllers and some ahcis don't save much when >>> only link power management is used, >> >> do you have data to support this? The data we have from this patch is >> that it saves typically a Watt of power (depends on the machine of >> course, but the range is 0.5W to 1.5W). If you want to also have an >> even more agressive thing where you want to start disabling the entire >> controller... I don't see how this is in conflict with saving power on >> the link level by "just" enabling a hardware feature .... > > SATA standard defines lower power phy states. So the same argument > you're using for AHCI applies there too -- "just" enabling an existing > hardware feature. > yes I'm not arguing against that. I was trying to find out (and suggest-unless-proven-otherwise) that the 2 are not exclusive or conflicting... in fact I assume both are wanted concurrently.