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=-2.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,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 97E39C3B189 for ; Thu, 13 Feb 2020 09:47:07 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 6F3F724649 for ; Thu, 13 Feb 2020 09:47:07 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729532AbgBMJrH (ORCPT ); Thu, 13 Feb 2020 04:47:07 -0500 Received: from foss.arm.com ([217.140.110.172]:44026 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729494AbgBMJrG (ORCPT ); Thu, 13 Feb 2020 04:47:06 -0500 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 0132A1FB; Thu, 13 Feb 2020 01:47:05 -0800 (PST) Received: from localhost (unknown [10.1.198.52]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 959CF3F6CF; Thu, 13 Feb 2020 01:47:05 -0800 (PST) Date: Thu, 13 Feb 2020 09:47:04 +0000 From: Ionela Voinescu To: Lukasz Luba Cc: catalin.marinas@arm.com, will@kernel.org, mark.rutland@arm.com, maz@kernel.org, suzuki.poulose@arm.com, sudeep.holla@arm.com, valentin.schneider@arm.com, rjw@rjwysocki.net, peterz@infradead.org, mingo@redhat.com, vincent.guittot@linaro.org, viresh.kumar@linaro.org, linux-arm-kernel@lists.infradead.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org Subject: Re: [PATCH v3 6/7] arm64: use activity monitors for frequency invariance Message-ID: <20200213094704.GA30335@arm.com> References: <20200211184542.29585-1-ionela.voinescu@arm.com> <20200211184542.29585-7-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 Hi Lukasz, [..] > > + > > +/* Obtain max frequency (in KHz) as reported by hardware */ > > +__weak unsigned int cpu_get_max_freq(unsigned int cpu) > > +{ > > + return 0; > > +} > > + > > +#ifdef CONFIG_CPU_FREQ > > +/* Replace max frequency getter with cpufreq based function */ > > +#define cpu_get_max_freq cpufreq_get_hw_max_freq > > +#endif > > Can we just use cpufreq_get_hw_max_freq()? > We have cpufreq_get_hw_max_freq returning 0 in such case, so it should > be OK. > The reasoning for the implementation is the following: - For CONFIG_CPU_FREQ we use cpufreq_get_hw_max_freq (weak default or strong alternative) - For !CONFIG_CPU_FREQ cpufreq_get_hw_max_freq returns 0 - it signals that cpufreq cannot return the hardware max frequency. In this case cpu_get_max_freq is used (weak default or strong alternative implementation). > Is there a possibility that some platform which has !CONFIG_CPU_FREQ > would define its own cpu_get_max_freq() overwriting the weak function > above? > Based on the code which checks 'if (unlikely(!max_freq_hz))' it should, > otherwise 'valid_cpus' is not set. > > I would assume that we won't see such platform, interested > in AMU freq invariance without CONFIG_CPU_FREQ. > > We already have a lot of these defines or __weak functions, which is > hard to follow. There is no dependency between CONFIG_CPU_FREQ and frequency invariance. Therefore, I did not see a reason to potentially bypass the use of AMU for frequency invariance for !CONFIG_CPU_FREQ. But I agree it makes the code harder to read so I can remove cpu_get_max_freq and keep cpufreq_get_hw_max_freq only until there is a provable need for this. Thank you for the review, Ionela.