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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 3E3F6C433FE for ; Tue, 8 Feb 2022 17:25:59 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1384231AbiBHRZ6 (ORCPT ); Tue, 8 Feb 2022 12:25:58 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:55230 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1384243AbiBHRZw (ORCPT ); Tue, 8 Feb 2022 12:25:52 -0500 Received: from mail-pf1-x435.google.com (mail-pf1-x435.google.com [IPv6:2607:f8b0:4864:20::435]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 49B53C06174F for ; Tue, 8 Feb 2022 09:25:51 -0800 (PST) Received: by mail-pf1-x435.google.com with SMTP id i30so20036103pfk.8 for ; Tue, 08 Feb 2022 09:25:51 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=chromium.org; s=google; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=cib/chw0Mb1unxiFkWS5LEJe9zXPAE/9BcI3EX7Nnkc=; b=FvN6s4uPYQxdJXKi2d2cz9Lqy70gKJqtodmmOFu08JZDwJTgLQIiEkwCPP2FYjCDgE rRofzWcTrybALgUCJRX5dAnfZql3swZiLe63nOFDM4i8zZhaN+vyNhIL6VKpgXKhcQxk 5Z1xRFoGYYrLsViFP56wB3J7wttAMRWmaEfJw= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=cib/chw0Mb1unxiFkWS5LEJe9zXPAE/9BcI3EX7Nnkc=; b=5NlLQS2wka1so4Iz8yZRCH/LQwb66MvhxlMbGQWdKbTwJk9Kro6UwFS6O8EIGTuV1Z 6MxKcDo1QFQV17oBt/6pHg6Ddkvoz9aeODHfa6NIvTvS0c6cLed8ISu2bRZiGeFIEvo/ li4fkDopmVBvX5f/iUo/y8H/vC2m1d+F5R4SA92y3lxG/7n/Y38YtsGpYDlo1FGpPF7r v82Rr9QQMnqfOB6fXc/S5tygN+4DKmbsdOASOVEPk/pHU41Hbhw5HcLA9U0+Cpl08Hop 3sMcIohTnPCWyR3FABiM76yuT5Bz5eS4S37ICBCj8T8EL0AmvE7c3XwqE7LMJHh/uemo HGiQ== X-Gm-Message-State: AOAM532BmL5j7Fmci/PKGhv0ghM4rzj070i7V3vEzemAB0qTBU6dPKLy W5SpF7tpNDVrCigFmOwE43nMpQ== X-Google-Smtp-Source: ABdhPJx49KZto+T/+N8XoEoYFIWssK5O2duMSNGvlQOF2cX43dpBYyMits2jwmbP1frpGxlAwM11bw== X-Received: by 2002:a63:2a95:: with SMTP id q143mr4415837pgq.492.1644341150692; Tue, 08 Feb 2022 09:25:50 -0800 (PST) Received: from localhost ([2620:15c:202:201:45cc:a522:8718:fc78]) by smtp.gmail.com with UTF8SMTPSA id z7sm16719798pfe.49.2022.02.08.09.25.49 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 08 Feb 2022 09:25:50 -0800 (PST) Date: Tue, 8 Feb 2022 09:25:48 -0800 From: Matthias Kaehlcke To: Lukasz Luba Cc: linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org, amit.kachhap@gmail.com, daniel.lezcano@linaro.org, viresh.kumar@linaro.org, rafael@kernel.org, amitk@kernel.org, rui.zhang@intel.com, dietmar.eggemann@arm.com, Pierre.Gondois@arm.com, Douglas Anderson , Stephen Boyd , Rajendra Nayak , Bjorn Andersson Subject: Re: [PATCH 1/2] thermal: cooling: Check Energy Model type in cpufreq_cooling and devfreq_cooling Message-ID: References: <20220207073036.14901-1-lukasz.luba@arm.com> <20220207073036.14901-2-lukasz.luba@arm.com> <4a7d4e94-1461-5bac-5798-29998af9793a@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <4a7d4e94-1461-5bac-5798-29998af9793a@arm.com> Precedence: bulk List-ID: X-Mailing-List: linux-pm@vger.kernel.org On Tue, Feb 08, 2022 at 09:32:28AM +0000, Lukasz Luba wrote: > > > On 2/8/22 12:50 AM, Matthias Kaehlcke wrote: > > On Mon, Feb 07, 2022 at 07:30:35AM +0000, Lukasz Luba wrote: > > > The Energy Model supports power values either in Watts or in some abstract > > > scale. When the 2nd option is in use, the thermal governor IPA should not > > > be allowed to operate, since the relation between cooling devices is not > > > properly defined. Thus, it might be possible that big GPU has lower power > > > values in abstract scale than a Little CPU. To mitigate a misbehaviour > > > of the thermal control algorithm, simply not register a cooling device > > > capable of working with IPA. > > > > Ugh, this would break thermal throttling for existing devices that are > > currently supported in the upstream kernel. > > Could you point me to those devices? I cannot find them in the mainline > DT. There are no GPU devices which register Energy Model (EM) in > upstream, neither using DT (which would be power in mW) nor explicitly > providing EM get_power() callback. The EM is needed to have IPA. > > Please clarify which existing devices are going to be broken with this > change. I was thinking about arch/arm64/boot/dts/qcom/sc7180-trogdor-*, and potentially other SC7180 boards that use IPA for the CPU thermal zones. Initially SC7180 used an abstract scale for the CPU energy model, however I realized your change doesn't actually impact SC7180 CPUs for two reasons: 1. The energy model of the CPUs is registered through cpufreq_register_em_with_opp dev_pm_opp_of_register_em em_dev_register_perf_domain em_dev_register_perf_domain() is called with 'milliwatts = true', regardless of the potentially abstract scale, so IPA would not be disabled with your change. 2. There is a patch from Doug that adjusted the dynamic power coefficients of the CPUs to be closer to reality: commit 82ea7d411d43f60dce878252558e926f957109f0 Author: Douglas Anderson Date: Thu Sep 2 14:51:37 2021 -0700 arm64: dts: qcom: sc7180: Base dynamic CPU power coefficients in reality > > Wasn't the conclusion that it is the responsability of the device tree > > owners to ensure that cooling devices with different scales aren't used > > in the same thermal zone? > > It's based on assumption that someone has DT and control. There was also > implicit assumption that IPA would work properly on such platform - but > it won't. > > 1. You cannot have 2 thermal zones: one with CPUs and other with GPU > only and both working with two instances of IPA. It's not clear to me why such a configuration wouldn't work. Is it also a problem to have multiple CPU thermal zones (one for each core) that use multiple instances of IPA? SC7180 has separate thermal zones for each core (or thermal sensor), Chrome OS uses IPA for CPU thermal throttling. > 2. The abstract power scale doesn't guaranty anything about power values > and IPA was simply designed with milli-Watts in mind. So even working > on CPUs only using bogoWatts, is not what we could guaranty in IPA. That's bad news for SoCs that are configured with bogoWatt values, from past discussions I had the impression that this is unfortunately not uncommon. > It's ugly to have the abstract scales in the first place, but that's > unfortunately what we currently have for at least some cooling devices. > A few questions: > > Do you use 'we' as Chrome engineers? I was referring to the kernel, in particular QCOM SC7180. > Could you point me to those devices please? arch/arm64/boot/dts/qcom/sc7180-trogdor-* Though as per above they shouldn't be impacted by your change, since the CPUs always pretend to use milli-Watts. [skipped some questions/answers since sc7180 isn't actually impacted by the change] Thanks Matthias