From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jeff Garzik Subject: Re: [patch 0/3] AHCI Link Power Management Date: Mon, 11 Jun 2007 23:12:48 -0400 Message-ID: <466E0F30.3000700@garzik.org> References: <20070611114600.7fca1c24.kristen.c.accardi@intel.com> <466DFDB5.9030901@gmail.com> <466E0642.5020506@linux.intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <466E0642.5020506@linux.intel.com> Sender: linux-scsi-owner@vger.kernel.org To: Arjan van de Ven 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-ide@vger.kernel.org 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. Jeff