From mboxrd@z Thu Jan 1 00:00:00 1970 From: Tim Bird Subject: Re: Embedded Linux power management Date: Fri, 30 May 2008 15:05:01 -0700 Message-ID: <48407A0D.3050802@am.sony.com> References: <483B5F0D.9060302@cs.drexel.edu> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <483B5F0D.9060302@cs.drexel.edu> Sender: linux-embedded-owner@vger.kernel.org List-ID: Content-Type: text/plain; charset="us-ascii"; format="flowed" To: J Sevy Cc: linux-embedded@vger.kernel.org J Sevy wrote: > Hi, > kind of a general question for the list concerning the current "state of > the art" in power management for handheld embedded Linux devices. In > particular: > - What are the standards in common use for power management on > handhelds? APM, ACPI, or something else? > - Is there a general consensus on the "best" approach for power management? > - Is Dynamic Power Management (i.e., "speed-stepping") widely used? > Thanks for any input. In general, PM on handhelds is heavily dependent on chip features. Many SOCs used in these devices have elaborate clock hardware, allowing you to adjust the voltage and frequency of various parts of the chip (or chipsets) dynamically. For some good overviews of different PM features relevant to embedded, you may want to look at the following papers: Every Microamp is Sacred - A Dynamic Voltage and Current Control Interface for the Linux Kernel - Liam Girdwood http://www.celinux.org/elc08_presentations/regulator-api-celf.pdf Power Management Quality of Service and How You Could Use it in Your Embedded Application - Mark Gross http://www.celinux.org/elc08_presentations/elc2008_pm_qos_slides.pdf Building Blocks for Embedded Power Management - Kevin Hilman http://www.celinux.org/elc08_presentations/PM_Building_Blocks1.pdf Linux Suspend-to-Disk Objectives for Consumer Electronic Devices - Vitaly Wool http://tree.celinuxforum.org/CelfPubWiki/ELCEurope2007Presentations?action=AttachFile&do=view&target=std.pdf Linux Clock Management Framework - Siarhei Yermalayeu http://tree.celinuxforum.org/CelfPubWiki/ELCEurope2007Presentations?action=AttachFile&do=view&target=ELC_2007_Linux_clock_fmw.pdf These links should probably be added to the Power Management page on the elinux wiki (http://elinux.org/Power_Management), which at the moment is fairly light on content. -- Tim ============================= Tim Bird Architecture Group Chair, CE Linux Forum Senior Staff Engineer, Sony Corporation of America =============================