From mboxrd@z Thu Jan 1 00:00:00 1970 From: Deepthi Dharwar Subject: Re: [RFC PATCH v2 4/4] cpuidle: (POWER) Handle power_save=off Date: Tue, 29 Nov 2011 12:14:24 +0530 Message-ID: <4ED47F48.2070107@linux.vnet.ibm.com> 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> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <1322512771.23348.45.camel@pasglop> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: linux-pm-bounces@lists.linux-foundation.org Errors-To: linux-pm-bounces@lists.linux-foundation.org To: Benjamin Herrenschmidt Cc: linuxppc-dev@ozlabs.org, linux-pm@lists.linux-foundation.org, linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org List-Id: linux-pm@vger.kernel.org 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