From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from e23smtp03.au.ibm.com (e23smtp03.au.ibm.com [202.81.31.145]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (Client CN "e23smtp03.au.ibm.com", Issuer "Equifax" (verified OK)) by ozlabs.org (Postfix) with ESMTPS id 8931EB7BD9 for ; Wed, 2 Dec 2009 20:55:55 +1100 (EST) Received: from d23relay03.au.ibm.com (d23relay03.au.ibm.com [202.81.31.245]) by e23smtp03.au.ibm.com (8.14.3/8.13.1) with ESMTP id nB29rAjt004050 for ; Wed, 2 Dec 2009 20:53:10 +1100 Received: from d23av01.au.ibm.com (d23av01.au.ibm.com [9.190.234.96]) by d23relay03.au.ibm.com (8.13.8/8.13.8/NCO v10.0) with ESMTP id nB29tsao1863918 for ; Wed, 2 Dec 2009 20:55:54 +1100 Received: from d23av01.au.ibm.com (loopback [127.0.0.1]) by d23av01.au.ibm.com (8.14.3/8.13.1/NCO v10.0 AVout) with ESMTP id nB29trU7031012 for ; Wed, 2 Dec 2009 20:55:54 +1100 Date: Wed, 2 Dec 2009 15:25:48 +0530 From: Arun R Bharadwaj To: Peter Zijlstra , Benjamin Herrenschmidt , Ingo Molnar , Vaidyanathan Srinivasan , Dipankar Sarma , Balbir Singh , Venkatesh Pallipadi , Arun Bharadwaj Subject: [v10 PATCH 1/9]: cpuidle: Design documentation patch Message-ID: <20091202095548.GB27251@linux.vnet.ibm.com> References: <20091202095427.GA27251@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 In-Reply-To: <20091202095427.GA27251@linux.vnet.ibm.com> Cc: linux-arch@vger.kernel.org, linux-acpi@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org Reply-To: arun@linux.vnet.ibm.com List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , * Arun R Bharadwaj [2009-12-02 15:24:27]: This patch adds a little information about the redesigned cpuidle infrastructure in Documentation/cpuidle/core.txt Signed-off-by: Arun R Bharadwaj --- Documentation/cpuidle/core.txt | 35 +++++++++++++++++++++++++++++++++++ 1 file changed, 35 insertions(+) Index: linux.trees.git/Documentation/cpuidle/core.txt =================================================================== --- linux.trees.git.orig/Documentation/cpuidle/core.txt +++ linux.trees.git/Documentation/cpuidle/core.txt @@ -21,3 +21,38 @@ which can be used to switch governors at is meant for developer testing only. In normal usage, kernel picks the best governor based on governor ratings. SEE ALSO: sysfs.txt in this directory. + +Design: + +Cpuidle allows for registration of multiple sets of idle routines. +The latest registered set is used by cpuidle governors as the current +active set to choose the right idle state. This set is managed as a +list and each time the newly registered set is added to the head of the +list and made the current active set. + +An example of how this would work on x86 is shown below. + +----------------- ----------------- +| | | | +| choose b/w | mwait is chosen | mwait | +| mwait, poll, |-------------------------------------> |(current active| +| default, c1e | register to cpuidle | set) | +| | with mwait as the idle routine | | +----------------- ----------------- + + +----------------- ----------------- +| | | c1, c2, c3 | +| ACPI | register to cpuidle | (current) | +| discovery |-------------------------------------> |---------------| +| | with c1, c2, c3 | mwait | +| | as set of idle routines | | +----------------- ----------------- + +With this mechanism, a module can register and unregister its set of +idle routines at run time in a clean manner. + +The main idle routine called inside cpu_idle() of every arch is defined in +driver/cpuidle/cpuidle.c which would in turn call the idle routine selected +by the governor. If the CONFIG_CPU_IDLE is disabled, the arch needs to +provide an alternate definition for cpuidle_idle_call().