From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from smtp.codeaurora.org by pdx-caf-mail.web.codeaurora.org (Dovecot) with LMTP id ILUuIn92GltUYQAAmS7hNA ; Fri, 08 Jun 2018 12:39:44 +0000 Received: by smtp.codeaurora.org (Postfix, from userid 1000) id A54D6608BA; Fri, 8 Jun 2018 12:39:44 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on pdx-caf-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.9 required=2.0 tests=BAYES_00,MAILING_LIST_MULTI autolearn=unavailable autolearn_force=no version=3.4.0 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by smtp.codeaurora.org (Postfix) with ESMTP id 1B43B607A4; Fri, 8 Jun 2018 12:39:44 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 smtp.codeaurora.org 1B43B607A4 Authentication-Results: pdx-caf-mail.web.codeaurora.org; dmarc=none (p=none dis=none) header.from=arm.com Authentication-Results: pdx-caf-mail.web.codeaurora.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752604AbeFHMjn (ORCPT + 25 others); Fri, 8 Jun 2018 08:39:43 -0400 Received: from foss.arm.com ([217.140.101.70]:33338 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751251AbeFHMjl (ORCPT ); Fri, 8 Jun 2018 08:39:41 -0400 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.72.51.249]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id ECF911529; Fri, 8 Jun 2018 05:39:40 -0700 (PDT) Received: from [0.0.0.0] (e107985-lin.cambridge.arm.com [10.1.210.41]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 95A453F557; Fri, 8 Jun 2018 05:39:35 -0700 (PDT) Subject: Re: [RFC PATCH v3 03/10] PM: Introduce an Energy Model management framework To: Quentin Perret Cc: Juri Lelli , peterz@infradead.org, rjw@rjwysocki.net, gregkh@linuxfoundation.org, linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org, mingo@redhat.com, morten.rasmussen@arm.com, chris.redpath@arm.com, patrick.bellasi@arm.com, valentin.schneider@arm.com, vincent.guittot@linaro.org, thara.gopinath@linaro.org, viresh.kumar@linaro.org, tkjos@google.com, joelaf@google.com, smuckle@google.com, adharmap@quicinc.com, skannan@quicinc.com, pkondeti@codeaurora.org, edubezval@gmail.com, srinivas.pandruvada@linux.intel.com, currojerez@riseup.net, javi.merino@kernel.org References: <20180521142505.6522-1-quentin.perret@arm.com> <20180521142505.6522-4-quentin.perret@arm.com> <20180607144409.GB3311@localhost.localdomain> <20180607151954.GA3597@e108498-lin.cambridge.arm.com> <52b9575b-4c2a-01df-fadd-10ccf3146112@arm.com> <20180608082511.GE3597@e108498-lin.cambridge.arm.com> From: Dietmar Eggemann Message-ID: <5a7b8177-7cbe-df90-7d00-8aad0a0f5f08@arm.com> Date: Fri, 8 Jun 2018 14:39:33 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.8.0 MIME-Version: 1.0 In-Reply-To: <20180608082511.GE3597@e108498-lin.cambridge.arm.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 06/08/2018 10:25 AM, Quentin Perret wrote: > Hi Dietmar, > > On Thursday 07 Jun 2018 at 17:55:32 (+0200), Dietmar Eggemann wrote: >> On 06/07/2018 05:19 PM, Quentin Perret wrote: >>> Hi Juri, >>> >>> On Thursday 07 Jun 2018 at 16:44:09 (+0200), Juri Lelli wrote: >>>> On 21/05/18 15:24, Quentin Perret wrote: [...] > The comment above em_register_freq_domain() explains that, at least > partially. In the current implementation, if multiple providers register > the same frequency domain, all but the first will be ignored. The reason > I implemented this that way is because: 1) it's simple; 2) it should > cover the current use-cases for EAS and IPA. > > But we could do something more clever. We could add a parameter to > em_register_freq_domain() that would represent some sort of priority. In > this case, if multiple providers register the same freq domain, the > higher priority would override the lower priority. For example, power > values coming from firmware could overwrite power values estimated with > P=CV^2f for example. In your current '(3)* Arm/Arm64 init code' (* see at the end of this email) you have this dev_pm_opp_of_estimate_power() em_data_callback active_power function. Let's say thermal and the task scheduler would initialize the EM independently. They would still end up using C from dt, and f, V and P from opp library in your example. IMHO, this information should be only provided once from one source per platform. >> The re-scaling thing comes from the requirement that the final cpu capacity >> values are only known after the arch_topology driver was able to scale the >> dmipz-capacity-values with the policy->cpuinfo.max_freq but why can't we >> create the EM on arm/arm64 after this? > > What if you don't have dmips-capacity-mhz values in the DT and still > want to use IPA ? There is no good reason to create a dependency between > the thermal subsystem and the arch_topology driver IMO. Mmmmh, that's correct. So it can't be simply called in init_cpu_capacity_callback() [drivers/base/arch_topology.c] in case the cpus_to_visit mask is empty. There is this dependency that cpufreq can be loaded at any time, requiring this re-scaling of capacity values ... That's not nice ... >> Even though we would be forced to get cpufreq's related cpumask from >> somewhere. > > That's the easy part. The difficult part is, where do you get power > values from ? You have to let the lower layers register those values > in a centralized location on a voluntary basis. And then it becomes easy > for consumers to access that data, because they know where it is. The code in the arch could use the same struct em_data_callback em_cb = { &dev_pm_opp_of_estimate_power } that the cpufreq driver is currently using? >> I guess the easiest model will be that the Energy Model (EM) is fully >> initialized with one init call (from the arch) and fixed after that. > > Again, I don't think that's possible. You have to let the lower layers > tell you where the power values come from, at the very least. You could > let the archs do that aggregation I suppose, but I don't really see the > benefit over one centralized framework with a generic interface ... > What's your opinion ? Don't understand the '... let the lower layers tell you where the power values come from ...' part. Where is the difference whether the arch or the cpufreq driver uses em_data_callback? [...] > So I think I'll drop patch 10/10 for v4 ... That part should be > discussed separately, with the rest of the Arm-specific changes. Maybe 3 clearly separated parts of the patch-set; (1) EM (2) EAS uses EM (3) Arm/Arm64 init code ? [...]