From patchwork Tue Feb 26 17:37:10 2013 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Nishanth Menon X-Patchwork-Id: 2186921 Return-Path: X-Original-To: patchwork-linux-pm@patchwork.kernel.org Delivered-To: patchwork-process-083081@patchwork2.kernel.org Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by patchwork2.kernel.org (Postfix) with ESMTP id 53D9ADF215 for ; Tue, 26 Feb 2013 17:37:46 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752743Ab3BZRhY (ORCPT ); Tue, 26 Feb 2013 12:37:24 -0500 Received: from comal.ext.ti.com ([198.47.26.152]:40325 "EHLO comal.ext.ti.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758522Ab3BZRhW (ORCPT ); Tue, 26 Feb 2013 12:37:22 -0500 Received: from dlelxv30.itg.ti.com ([172.17.2.17]) by comal.ext.ti.com (8.13.7/8.13.7) with ESMTP id r1QHbHdE013513; Tue, 26 Feb 2013 11:37:17 -0600 Received: from DFLE73.ent.ti.com (dfle73.ent.ti.com [128.247.5.110]) by dlelxv30.itg.ti.com (8.13.8/8.13.8) with ESMTP id r1QHbHrq006776; Tue, 26 Feb 2013 11:37:17 -0600 Received: from dlelxv22.itg.ti.com (172.17.1.197) by dfle73.ent.ti.com (128.247.5.110) with Microsoft SMTP Server id 14.1.323.3; Tue, 26 Feb 2013 11:37:17 -0600 Received: from localhost (kahuna.am.dhcp.ti.com [128.247.75.12]) by dlelxv22.itg.ti.com (8.13.8/8.13.8) with ESMTP id r1QHbHVB029230; Tue, 26 Feb 2013 11:37:17 -0600 From: Nishanth Menon To: linux-pm CC: Linus Torvalds , Nishanth Menon , "Rafael J. Wysocki" , , Subject: [PATCH] PM / OPP: improve introductory documentation Date: Tue, 26 Feb 2013 11:37:10 -0600 Message-ID: <1361900231-10478-1-git-send-email-nm@ti.com> X-Mailer: git-send-email 1.7.9.5 MIME-Version: 1.0 Sender: linux-pm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-pm@vger.kernel.org Make Operating Performance Points (OPP) library introductory chapter a little more reader-friendly. Split the chapter into two sections and highlight the definition with an example. Reported-by: Linus Torvalds Cc: "Rafael J. Wysocki" Cc: linux-pm@vger.kernel.org Cc: linux-doc@vger.kernel.org Cc: linux-kernel@vger.kernel.org Signed-off-by: Nishanth Menon --- based on v3.8 tag Documentation/power/opp.txt | 23 +++++++++++++++++++---- 1 file changed, 19 insertions(+), 4 deletions(-) diff --git a/Documentation/power/opp.txt b/Documentation/power/opp.txt index 3035d00..b4f1870 100644 --- a/Documentation/power/opp.txt +++ b/Documentation/power/opp.txt @@ -1,6 +1,5 @@ -*=============* -* OPP Library * -*=============* +Operating Performance Points (OPP) Library +========================================== (C) 2009-2010 Nishanth Menon , Texas Instruments Incorporated @@ -16,15 +15,31 @@ Contents 1. Introduction =============== +1.1 What is an Operating Performance Point (OPP)? + Complex SoCs of today consists of a multiple sub-modules working in conjunction. In an operational system executing varied use cases, not all modules in the SoC need to function at their highest performing frequency all the time. To facilitate this, sub-modules in a SoC are grouped into domains, allowing some domains to run at lower voltage and frequency while other domains are loaded -more. The set of discrete tuples consisting of frequency and voltage pairs that +more. + +The set of discrete tuples consisting of frequency and voltage pairs that the device will support per domain are called Operating Performance Points or OPPs. +As an example: +Let us consider an MPU device which supports the following: +{300MHz at minimum voltage of 1V}, {800MHz at minimum voltage of 1.2V}, +{1GHz at minimum voltage of 1.3V} + +We can represent these as three OPPs as the following {Hz, uV} tuples: +{300000000, 1000000} +{600000000, 1200000} +{100000000, 1300000} + +1.2 Operating Performance Points Library + OPP library provides a set of helper functions to organize and query the OPP information. The library is located in drivers/base/power/opp.c and the header is located in include/linux/opp.h. OPP library can be enabled by enabling