Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752127AbaBQIjH (ORCPT ); Mon, 17 Feb 2014 03:39:07 -0500 Received: from mail-oa0-f52.google.com ([209.85.219.52]:39508 "EHLO mail-oa0-f52.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750930AbaBQIjE (ORCPT ); Mon, 17 Feb 2014 03:39:04 -0500 MIME-Version: 1.0 In-Reply-To: <5301C605.3030205@linux.vnet.ibm.com> References: <15ccc0609cb9ee3db0ad3a95b29bf69d11ea197c.1392375504.git.viresh.kumar@linaro.org> <4772234.6D4cUIJHX4@vostro.rjw.lan> <5301C605.3030205@linux.vnet.ibm.com> Date: Mon, 17 Feb 2014 14:09:03 +0530 Message-ID: Subject: Re: [PATCH 1/2] cpufreq: Return error if ->get() failed in cpufreq_update_policy() From: Viresh Kumar To: "Srivatsa S. Bhat" Cc: "Rafael J. Wysocki" , Lists linaro-kernel , "cpufreq@vger.kernel.org" , "linux-pm@vger.kernel.org" , Linux Kernel Mailing List , Pierre Ossman Content-Type: text/plain; charset=ISO-8859-1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 17 February 2014 13:49, Srivatsa S. Bhat wrote: > Quick question: Looking at cpufreq_update_policy() and cpufreq_out_of_sync(), > I understand that if the cpufreq subsystem's notion of the current frequency > does not match with the actual frequency of the CPU, it tries to adjust and > notify everyone that the current frequency is so-and-so, as read from the > hardware. Instead, why can't we simply set the frequency to the value that > we _want_ it to be at? I mean, if cpufreq subsystem thinks it is X KHz and > the actual frequency is Y KHz, we can as well fix the anomaly by setting the > frequency immediately to X KHz right? > > The reason I ask this is that, if we follow this approach, then we can avoid > ambiguities in dealing with the out-of-sync situation. That is, it becomes > very straightforward to decide _what_ to do, when we detect scenarios where > the frequency goes out of sync. Hmm, it is just about doing all that stuff in a single line, like: __cpufreq_driver_target(...) ?? There are few problems here: - If we simply call above routine with X, then it will simply return as X == policy->cur. And I don't want to hack this code in a bad way now :) - So, probably the way it is implemented is right, as we do that the most efficient way. We just broadcast the new freq in case there is a difference otherwise nothing. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/