Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752213AbdGMOGT (ORCPT ); Thu, 13 Jul 2017 10:06:19 -0400 Received: from foss.arm.com ([217.140.101.70]:38908 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751193AbdGMOGR (ORCPT ); Thu, 13 Jul 2017 10:06:17 -0400 Cc: Sudeep Holla , Peter Zijlstra , "Rafael J. Wysocki" , Linux Kernel Mailing List , Linux PM , Russell King - ARM Linux , Greg Kroah-Hartman , Russell King , Catalin Marinas , Will Deacon , Juri Lelli , Vincent Guittot , Morten Rasmussen Subject: Re: [PATCH v2 02/10] cpufreq: provide data for frequency-invariant load-tracking support To: Dietmar Eggemann , Viresh Kumar , "Rafael J. Wysocki" References: <20170706094948.8779-1-dietmar.eggemann@arm.com> <12829054.TWIodSo4bb@aspire.rjw.lan> <20170710065443.GG2928@vireshk-i7> <4673356.gkeX7KYvlb@aspire.rjw.lan> <20170711063944.GA17115@vireshk-i7> From: Sudeep Holla Organization: ARM Message-ID: <5172dfcb-2d4c-6f90-671c-bd3639b44aab@arm.com> Date: Thu, 13 Jul 2017 15:06:12 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.2.1 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1460 Lines: 44 On 13/07/17 14:08, Dietmar Eggemann wrote: > On 13/07/17 13:40, Sudeep Holla wrote: >> >> >> On 11/07/17 16:21, Dietmar Eggemann wrote: >>> On 11/07/17 07:39, Viresh Kumar wrote: >>>> On 10-07-17, 14:46, Rafael J. Wysocki wrote: > > [...] > >>> Like I said in the other email, since for (future) >>> arm/arm64 fast-switch driver, the return value of >>> cpufreq_driver->fast_switch() does not give us the information that the >>> frequency value did actually change, we have to implement >> >> I was under the impression that we strictly don't care about that >> information when I started exploring the fast_switch with the standard >> firmware interface on ARM platforms(until if and when ARM provides an >> instruction to achieve that). >> >> If f/w failed to change the frequency, will that be not corrected in the >> next sample or instance. I would like to know the impact of absence of >> such notifications. > > In the meantime we agreed that we have to invoke frequency invariance > from within the cpufreq driver. > > For a fast-switch driver I would have to put the call to > arch_set_freq_scale() somewhere where I know that the frequency has been > set. > > Without a notification (from the firmware) that the frequency has been > set, I would have to call arch_set_freq_scale() somewhere in the > driver::fast_switch() call assuming that the frequency has been actually > set. > Yes, that's what I was thinking too. -- Regards, Sudeep