From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-5.5 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 57B89C433DF for ; Wed, 29 Jul 2020 09:14:19 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 3D5B7206D4 for ; Wed, 29 Jul 2020 09:14:19 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727007AbgG2JOS (ORCPT ); Wed, 29 Jul 2020 05:14:18 -0400 Received: from foss.arm.com ([217.140.110.172]:48378 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726336AbgG2JOS (ORCPT ); Wed, 29 Jul 2020 05:14:18 -0400 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 98600101E; Wed, 29 Jul 2020 02:14:17 -0700 (PDT) Received: from localhost (unknown [10.1.198.53]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 3A2E43F718; Wed, 29 Jul 2020 02:14:17 -0700 (PDT) Date: Wed, 29 Jul 2020 10:14:15 +0100 From: Ionela Voinescu To: "Rafael J. Wysocki" Cc: "Rafael J. Wysocki" , Viresh Kumar , Dietmar Eggemann , Catalin Marinas , Sudeep Holla , Will Deacon , Russell King - ARM Linux , Ingo Molnar , Peter Zijlstra , Linux PM , Linux ARM , Linux Kernel Mailing List Subject: Re: [PATCH v2 2/7] cpufreq: set invariance scale factor on transition end Message-ID: <20200729091405.GB12941@arm.com> References: <20200722093732.14297-1-ionela.voinescu@arm.com> <20200722093732.14297-3-ionela.voinescu@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.9.4 (2018-02-28) Sender: linux-pm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-pm@vger.kernel.org On Monday 27 Jul 2020 at 15:52:41 (+0200), Rafael J. Wysocki wrote: > On Wed, Jul 22, 2020 at 11:38 AM Ionela Voinescu > wrote: > > > > While the move of the invariance setter calls (arch_set_freq_scale()) > > from cpufreq drivers to cpufreq core maintained the previous > > functionality for existing drivers that use target_index() and > > fast_switch() for frequency switching, it also gives the possibility > > of adding support for users of the target() callback, which is exploited > > here. > > > > To be noted that the target() callback has been flagged as deprecated > > since: > > > > commit 9c0ebcf78fde ("cpufreq: Implement light weight ->target_index() routine") > > > > It also doesn't have that many users: > > > > cpufreq-nforce2.c:371:2: .target = nforce2_target, > > cppc_cpufreq.c:416:2: .target = cppc_cpufreq_set_target, > > gx-suspmod.c:439:2: .target = cpufreq_gx_target, > > pcc-cpufreq.c:573:2: .target = pcc_cpufreq_target, > > > > Similarly to the path taken for target_index() calls in the cpufreq core > > during a frequency change, all of the drivers above will mark the end of a > > frequency change by a call to cpufreq_freq_transition_end(). > > > > Therefore, cpufreq_freq_transition_end() can be used as the location for > > the arch_set_freq_scale() call to potentially inform the scheduler of the > > frequency change. > > > > This change maintains the previous functionality for the drivers that > > implement the target_index() callback, while also adding support for the > > few drivers that implement the deprecated target() callback. > > > > Two notes are worthwhile here: > > - In __target_index(), cpufreq_freq_transition_end() is called only for > > drivers that have synchronous notifications enabled. There is only one > > driver that disables them, > > > > drivers/cpufreq/powernow-k8.c:1142: .flags = CPUFREQ_ASYNC_NOTIFICATION, > > > > which is deprecated. > > > > - Despite marking a successful frequency change, many cpufreq drivers > > will populate the new policy->cur with the new requested frequency, > > although this might not be the one granted by the hardware. > > > > Therefore, the call to arch_set_freq_scale() is a "best effort" one, > > and it is up to the architecture if the new frequency is used in the > > new frequency scale factor setting or eventually used by the scheduler. > > The architecture is in a better position to decide if it has better > > methods to obtain more accurate information regarding the current > > frequency (for example the use of counters). > > [..] > I would fold this patch into the previous one. > > I don't see much reason for it to be separate and it looks like > folding it in would cause the previous patch to be simpler. I kept it separate in this version as a proposal to move the call to cpufreq_freq_transition_end() and properly justify it in the commit message. I'll squash it into the previous one, as recommended. Thanks, Ionela.