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 B1E53C433E6 for ; Thu, 4 Mar 2021 13:49:22 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 76A9C64F52 for ; Thu, 4 Mar 2021 13:49:22 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S241476AbhCDNsf (ORCPT ); Thu, 4 Mar 2021 08:48:35 -0500 Received: from foss.arm.com ([217.140.110.172]:38514 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S238758AbhCDNsa (ORCPT ); Thu, 4 Mar 2021 08:48:30 -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 30CE731B; Thu, 4 Mar 2021 05:47:44 -0800 (PST) Received: from [10.57.19.206] (unknown [10.57.19.206]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id BAF7F3F766; Thu, 4 Mar 2021 05:47:39 -0800 (PST) Subject: Re: [PATCH] devfreq: Register devfreq as a cooling device To: Daniel Lezcano Cc: cwchoi00@gmail.com, kyungmin.park@samsung.com, myungjoo.ham@samsung.com, linux-pm@vger.kernel.org, linux-kernel@vger.kernel.org, Chanwoo Choi , Qiang Yu , David Airlie , Daniel Vetter , Rob Clark , Sean Paul , Rob Herring , Tomeu Vizoso , Steven Price , Alyssa Rosenzweig , "open list:DRM DRIVERS FOR LIMA" , "moderated list:DRM DRIVERS FOR LIMA" , "open list:DRM DRIVER FOR MSM ADRENO GPU" , "open list:DRM DRIVER FOR MSM ADRENO GPU" References: <20210304125034.28404-1-daniel.lezcano@linaro.org> From: Lukasz Luba Message-ID: <5f06e0c5-b2d9-5e11-01b6-fdd0dac635a7@arm.com> Date: Thu, 4 Mar 2021 13:47:37 +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: <20210304125034.28404-1-daniel.lezcano@linaro.org> 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-kernel@vger.kernel.org Hi Daniel, On 3/4/21 12:50 PM, Daniel Lezcano wrote: > Currently the default behavior is to manually having the devfreq > backend to register themselves as a devfreq cooling device. > > There are no so many and actually it makes more sense to register the > devfreq device when adding it. > > Consequently, every devfreq becomes a cooling device like cpufreq is. > > Having a devfreq being registered as a cooling device can not mitigate > a thermal zone if it is not bound to this one. Thus, the current > configurations are not impacted by this change. There are also different type of devices, which register into devfreq framework like NoC buses, UFS/eMMC, jpeg and video accelerators, ISP, etc. In some platforms there are plenty of those devices and they all would occupy memory due to private freq_table in devfreq_cooling, function: devfreq_cooling_gen_tables(). IIRC in OdroidXU4 there are ~20 devfreq devs for NoC buses. It's true that they will not affect thermal zones, but unnecessarily, they all will show up in the /sys/class/thermal/ as thermal-devfreq-X. IMO the devfreq shouldn't be tight with devfreq cooling thermal. CpuFreq is different because it handles only CPUs. Here we have many different devices. Regards, Lukasz