From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S965055AbVHJKHV (ORCPT ); Wed, 10 Aug 2005 06:07:21 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S965058AbVHJKHV (ORCPT ); Wed, 10 Aug 2005 06:07:21 -0400 Received: from gprs189-60.eurotel.cz ([160.218.189.60]:4320 "EHLO amd.ucw.cz") by vger.kernel.org with ESMTP id S965055AbVHJKHU (ORCPT ); Wed, 10 Aug 2005 06:07:20 -0400 Date: Wed, 10 Aug 2005 12:07:18 +0200 From: Pavel Machek To: Todd Poynor Cc: linux-kernel@vger.kernel.org, linux-pm@lists.osdl.org, cpufreq@www.linux.org.uk Subject: Re: PowerOP 0/3: System power operating point management API Message-ID: <20050810100718.GC1945@elf.ucw.cz> References: <20050809024907.GA25064@slurryseal.ddns.mvista.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20050809024907.GA25064@slurryseal.ddns.mvista.com> X-Warning: Reading this can be dangerous to your mental health. User-Agent: Mutt/1.5.9i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Hi! > PowerOP is a system power parameter management API submitted for > discussion. PowerOP writes and reads power "operating points", > comprised of arbitrary integer-valued values, called power parameters, > that correspond to registers, clocks, dividers, voltage regulators, > etc. that may be modified to set a basic power/performance point for the > system. The core basically passes an array of integer-valued power > parameters (with very little additional structure imposed by the core) > to a platform-specific backend that interprets those values and makes > the requested adjustments. PowerOP is intended to leave all power > policy decisions to higher layers. An optional sysfs representation of > power parameters is also available, primarily for diagnostic use. > > PowerOP can be thought of as a layer below cpufreq that actually > accesses the hardware to make cpu frequency, voltage, core bus, and > perhaps other modifications to set a power point, leaving cpufreq to > manage the interfaces based around the "cpu frequency" abstraction, the > policies and governors that select the frequency, its notifiers, and so > forth. An example hooking up support for one cpufreq platform to > PowerOP is in patch 3/3. > > Depending on the ability of the hardware to make software-controlled > power/performance adjustments, this may be useful to select custom > voltages, bus speeds, etc. in desktop/server systems. Various embedded > systems have several parameters that can be set. For example, an XScale > PXA27x could be considered to have six basic power parameters (mainly > cpu run mode and memory and bus dividers) that for the most part > should This scares me a bit. Is table enough to handle this? I'm afraid that table will get very large on systems that allow you to do "almost anything". Pavel -- if you have sharp zaurus hardware you don't need... you know my address