From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from e23smtp05.au.ibm.com (e23smtp05.au.ibm.com [202.81.31.147]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (Client CN "e23smtp05.au.ibm.com", Issuer "GeoTrust SSL CA" (verified OK)) by ozlabs.org (Postfix) with ESMTPS id 658A1B6F94 for ; Tue, 29 Nov 2011 17:44:31 +1100 (EST) Received: from /spool/local by e23smtp05.au.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Tue, 29 Nov 2011 06:42:23 +1000 Received: from d23av04.au.ibm.com (d23av04.au.ibm.com [9.190.235.139]) by d23relay04.au.ibm.com (8.13.8/8.13.8/NCO v10.0) with ESMTP id pAT6f37J3559626 for ; Tue, 29 Nov 2011 17:41:03 +1100 Received: from d23av04.au.ibm.com (loopback [127.0.0.1]) by d23av04.au.ibm.com (8.14.4/8.13.1/NCO v10.0 AVout) with ESMTP id pAT6iRLM021683 for ; Tue, 29 Nov 2011 17:44:27 +1100 Message-ID: <4ED47F48.2070107@linux.vnet.ibm.com> Date: Tue, 29 Nov 2011 12:14:24 +0530 From: Deepthi Dharwar MIME-Version: 1.0 To: Benjamin Herrenschmidt Subject: Re: [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> In-Reply-To: <1322512771.23348.45.camel@pasglop> Content-Type: text/plain; charset=ISO-8859-1 Cc: linuxppc-dev@ozlabs.org, linux-pm@lists.linux-foundation.org, linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , 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. >> >> 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