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=-15.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_SANE_1 autolearn=unavailable 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 31BBCC4332E for ; Fri, 12 Mar 2021 10:27:09 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 0365664FDD for ; Fri, 12 Mar 2021 10:27:08 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233450AbhCLKWn (ORCPT ); Fri, 12 Mar 2021 05:22:43 -0500 Received: from foss.arm.com ([217.140.110.172]:50900 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233314AbhCLKWe (ORCPT ); Fri, 12 Mar 2021 05:22:34 -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 08C391FB; Fri, 12 Mar 2021 02:22:33 -0800 (PST) Received: from [10.57.17.106] (unknown [10.57.17.106]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 177C23F70D; Fri, 12 Mar 2021 02:22:31 -0800 (PST) Subject: Re: [PATCH v3 1/5] powercap/drivers/dtpm: Encapsulate even more the code From: Lukasz Luba To: Daniel Lezcano Cc: rafael@kernel.org, linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org References: <20210310110212.26512-1-daniel.lezcano@linaro.org> Message-ID: <2f149f7f-5a69-2f0a-07f7-f01644e09c53@arm.com> Date: Fri, 12 Mar 2021 10:22:30 +0000 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: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 3/12/21 10:11 AM, Lukasz Luba wrote: > > > On 3/11/21 10:57 AM, Daniel Lezcano wrote: >> On 11/03/2021 11:15, Lukasz Luba wrote: >>> Hi Daniel, >>> >>> On 3/10/21 11:02 AM, Daniel Lezcano wrote: >>>> In order to increase the self-encapsulation of the dtpm generic code, >>>> the following changes are adding a power update ops to the dtpm >>>> ops. That allows the generic code to call directly the dtpm backend >>>> function to update the power values. >>>> >>>> The power update function does compute the power characteristics when >>>> the function is invoked. In the case of the CPUs, the power >>>> consumption depends on the number of online CPUs. The online CPUs mask >>>> is not up to date at CPUHP_AP_ONLINE_DYN state in the tear down >>>> callback. That is the reason why the online / offline are at separate >>>> state. As there is already an existing state for DTPM, this one is >>>> only moved to the DEAD state, so there is no addition of new state >>>> with these changes. The dtpm node is not removed when the cpu is >>>> unplugged. >>>> >>>> That simplifies the code for the next changes and results in a more >>>> self-encapsulated code. >>>> >>>> Signed-off-by: Daniel Lezcano >>>> --- >>>> V2: >>>>    - Updated the changelog with the CPU node not being removed >>>>    - Commented the cpu hotplug callbacks to explain why there are two >>>> callbacks >>>>    - Changed 'upt_power_uw' to 'update_power_uw' >>>>    - Removed unused cpumask variable >>>> --- >>>>    drivers/powercap/dtpm.c     |  54 ++++++------- >>>>    drivers/powercap/dtpm_cpu.c | 148 >>>> ++++++++++++++++-------------------- >>>>    include/linux/cpuhotplug.h  |   2 +- >>>>    include/linux/dtpm.h        |   3 +- >>>>    4 files changed, 97 insertions(+), 110 deletions(-) >>>> >>> >>> [snip] >>> >>>> @@ -210,27 +175,20 @@ static int cpuhp_dtpm_cpu_online(unsigned int >>>> cpu) >>>>        for_each_cpu(cpu, policy->related_cpus) >>>>            per_cpu(dtpm_per_cpu, cpu) = dtpm; >>>>    -    sprintf(name, "cpu%d", dtpm_cpu->cpu); >>>> +    sprintf(name, "cpu%d-cpufreq", dtpm_cpu->cpu); >>> >>> We should be safe in normal platforms, since there is less than >>> < 300 cores. although, I would use 2x CPUFREQ_NAME_LEN array. >> >> I'm counting 9999 cores. >> >> We have: >> #define CPUFREQ_NAME_LEN 16 >> >> "cpu-cpufreq\0" counts 12 characters. >> >> There are 4 characters left, 9999 max then, no ? > > Yes, my '< 300' was referring to some server platforms, > which IIRC had 2 sockets, each with 128 cores. I don't > know about future, though. > >> >> The code is designed for cpufreq with the energy model which targets >> ARM64 architecture and AFAICT we are far away of having so many cores on >> our phones. > > True, otherwise with such big number of cores in mobile, we would face > probably more hard to investigate issues, than this simple one ;) > >> >> Except I'm wrong, I would prefer to keep the current CPUFREQ_NAME_LEN to >> not introduce subtle bugs (like stack overflow) if the length is >> increased in cpufreq.h. >> >> What do you think ? > > Agree, please skip my former comment and just take the reviewed tag. What you could do, though, is to use: snprintf(name, sizeof(name), "cpu%d-cpufreq", dtpm_cpu->cpu); just to play safe.