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=-5.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,NICE_REPLY_A,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 8EBC5C432BE for ; Tue, 10 Aug 2021 13:25:46 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 7301261076 for ; Tue, 10 Aug 2021 13:25:44 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S241327AbhHJN0E (ORCPT ); Tue, 10 Aug 2021 09:26:04 -0400 Received: from foss.arm.com ([217.140.110.172]:55352 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S241448AbhHJNZn (ORCPT ); Tue, 10 Aug 2021 09:25:43 -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 350041FB; Tue, 10 Aug 2021 06:25:21 -0700 (PDT) Received: from [10.57.9.181] (unknown [10.57.9.181]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 8EF013F70D; Tue, 10 Aug 2021 06:25:16 -0700 (PDT) Subject: Re: [PATCH 0/8] cpufreq: Auto-register with energy model To: Quentin Perret Cc: Viresh Kumar , Rafael Wysocki , Vincent Donnefort , Andy Gross , Bjorn Andersson , Cristian Marussi , Fabio Estevam , Kevin Hilman , Matthias Brugger , NXP Linux Team , Pengutronix Kernel Team , Sascha Hauer , Shawn Guo , Sudeep Holla , linux-pm@vger.kernel.org, Vincent Guittot , linux-arm-kernel@lists.infradead.org, linux-arm-msm@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mediatek@lists.infradead.org, linux-omap@vger.kernel.org References: From: Lukasz Luba Message-ID: Date: Tue, 10 Aug 2021 14:25:15 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.9.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-arm-msm@vger.kernel.org On 8/10/21 1:35 PM, Quentin Perret wrote: > On Tuesday 10 Aug 2021 at 13:06:47 (+0530), Viresh Kumar wrote: >> Provide a cpufreq driver flag so drivers can ask the cpufreq core to register >> with the EM core on their behalf. > > Hmm, that's not quite what this does. This asks the cpufreq core to > use *PM_OPP* to register an EM, which I think is kinda wrong to do from > there IMO. The decision to use PM_OPP or another mechanism to register > an EM belongs to platform specific code (drivers), so it is odd for the > PM_OPP registration to have its own cpufreq flag but not the other ways. > > As mentioned in another thread, the very reason to have PM_EM is to not > depend on PM_OPP, so I'm worried about the direction of travel with this > series TBH. > >> This allows us to get rid of duplicated code >> in the drivers and fix the unregistration part as well, which none of the >> drivers have done until now. > > This series adds more code than it removes, and the unregistration is > not a fix as we don't ever remove the EM tables by design, so not sure > either of these points are valid arguments. > >> This would also make the registration with EM core to happen only after policy >> is fully initialized, and the EM core can do other stuff from in there, like >> marking frequencies as inefficient (WIP). Though this patchset is useful without >> that work being done and should be merged nevertheless. >> >> This doesn't update scmi cpufreq driver for now as it is a special case and need >> to be handled differently. Though we can make it work with this if required. > > Note that we'll have more 'special cases' if other architectures start > using PM_EM, which is what we have been trying to allow since the > beginning, so that's worth keeping in mind. > The way I see this is that the flag in cpufreq avoids mistakes potentially made by driver developer. It will automaticaly register the *simple* EM model via dev_pm_opp_of_register_em() on behalf of drivers (which is already done manually by drivers). The developer would just set the flag similarly to CPUFREQ_IS_COOLING_DEV and be sure it will register at the right time. Well tested flag approach should be safer, easier to understand, maintain. If there is a need for *advanced* EM model, driver developer would have to care about all these things (order, setup-ready-structures, fw channels, freeing, etc) while developing custom registration. The developer won't set this flag in such case, so the core won't try to auto register the EM for that driver. I don't see the dependency of PM_EM on PM_OPP in this series.