From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757369Ab1K3B0I (ORCPT ); Tue, 29 Nov 2011 20:26:08 -0500 Received: from e23smtp02.au.ibm.com ([202.81.31.144]:58039 "EHLO e23smtp02.au.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754661Ab1K3B0F (ORCPT ); Tue, 29 Nov 2011 20:26:05 -0500 Message-ID: <4ED58614.9090204@linux.vnet.ibm.com> Date: Wed, 30 Nov 2011 06:55:40 +0530 From: Deepthi Dharwar User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.9.2.23) Gecko/20110922 Thunderbird/3.1.15 MIME-Version: 1.0 To: Deepthi Dharwar CC: Benjamin Herrenschmidt , linuxppc-dev@ozlabs.org, linux-pm@lists.linux-foundation.org, linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org Subject: Re: [linux-pm] [RFC PATCH v2 4/4] cpuidle: (POWER) Handle power_save=off References: <20111117112815.9191.2322.stgit@localhost6.localdomain6> <20111117112906.9191.54050.stgit@localhost6.localdomain6> <1322435233.23348.19.camel@pasglop> <4ED36A7D.9070308@linux.vnet.ibm.com> <1322512771.23348.45.camel@pasglop> <4ED47F48.2070107@linux.vnet.ibm.com> In-Reply-To: <4ED47F48.2070107@linux.vnet.ibm.com> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit x-cbid: 11112915-5490-0000-0000-00000039906A Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 11/29/2011 12:14 PM, Deepthi Dharwar wrote: > On 11/29/2011 02:09 AM, Benjamin Herrenschmidt wrote: > >> On Mon, 2011-11-28 at 16:33 +0530, Deepthi Dharwar wrote: >> >>> On an LPAR if cpuidle is disabled, ppc_md.power_save is still set to >>> cpuidle_idle_call by default here. This would result in calling of >>> cpuidle_idle_call repeatedly, only for the call to return -ENODEV. The >>> default idle is never executed. >>> This would be a major design flaw. No fallback idle routine. >>> >>> We propose to fix this by checking the return value of >>> ppc_md.power_save() call from void to int. >>> Right now return value is void, but if we change this to int, this >>> would solve two problems. One being removing the cast to a function >>> pointer in the prev patch and this design flaw stated above. kernel/idle.c: ppc_md.power_save = NULL; >>> >>> So by checking the return value of ppc_md.power_save(), we can invoke >>> the default idle on failure. But my only concern is about the effects of >>> changing the ppc_md.power_save() to return int on other powerpc >>> architectures. Would it be a good idea to change the return type to int >>> which would help us flag an error and fallback to default idle? >> >> I would have preferred an approach where the cpuidle module sets >> ppc_md.power_save when loaded and restores it when unloaded ... but that >> would have to go into the cpuidle core as a powerpc specific tweak and >> might not be generally well received. >> >> So go for it, add the return value, but you'll have to update all the >> idle functions (grep for power_save in arch/powerpc to find them). >> > > > Thanks Ben. Yes, I will update all the idle functions under powerpc. > I will re-work these patches with the discussed changes. > > Regards, > Deepthi > > _______________________________________________ > linux-pm mailing list > linux-pm@lists.linux-foundation.org > https://lists.linuxfoundation.org/mailman/listinfo/linux-pm > > Hi Ben, I was trying to add a return value for power_save for all arch/powepc idle functions but a few of them directly call *.S routines, as they are asm. What would be a good way to change the return value for asm routines ? Do we make a change in asm only, put the return value in r3 or write a wrapper function which would call these asm routines and return an int ? Regards, Deepthi