From mboxrd@z Thu Jan 1 00:00:00 1970 From: Viresh Kumar Subject: Re: [PATCH 8/8] thermal/drivers/cpu_cooling: Add the combo cpu cooling device Date: Mon, 5 Feb 2018 09:47:34 +0530 Message-ID: <20180205041734.GD28462@vireshk-i7> References: <1516721671-16360-1-git-send-email-daniel.lezcano@linaro.org> <1516721671-16360-9-git-send-email-daniel.lezcano@linaro.org> <20180202104259.GA28462@vireshk-i7> <8dadd854-25ac-68aa-aa9f-33ba76a137a4@linaro.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Received: from mail-pl0-f47.google.com ([209.85.160.47]:44980 "EHLO mail-pl0-f47.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752253AbeBEERi (ORCPT ); Sun, 4 Feb 2018 23:17:38 -0500 Received: by mail-pl0-f47.google.com with SMTP id f8so10963894plk.11 for ; Sun, 04 Feb 2018 20:17:38 -0800 (PST) Content-Disposition: inline In-Reply-To: <8dadd854-25ac-68aa-aa9f-33ba76a137a4@linaro.org> Sender: linux-pm-owner@vger.kernel.org List-Id: linux-pm@vger.kernel.org To: Daniel Lezcano Cc: edubezval@gmail.com, kevin.wangtao@linaro.org, leo.yan@linaro.org, vincent.guittot@linaro.org, amit.kachhap@gmail.com, linux-kernel@vger.kernel.org, Zhang Rui , Javi Merino , "open list:THERMAL" , daniel.thompson@linaro.org On 02-02-18, 15:30, Daniel Lezcano wrote: > On 02/02/2018 11:42, Viresh Kumar wrote: > > Here is how I see the whole thing now: > > > > - Yes we need individual support for both cpufreq and cpuidle cooling devices, > > and no one disagrees on that I believe. > > > > - There is nothing in the thermal framework that disallows both cpufreq and > > cpuidle cooling devices to co-exist. Both would be part of the same thermal > > zone and so will get throttled with the same thermal sensor event. And so we > > will end up trying to cool down the SoC using both cpufreq and cpuidle > > technique. > > No. It does not work because we will need different state for each > cooling device and we need some logic behind. Right, but I thought the cooling-maps can help us specify different cooling states for different cooling devices for the same trip point. Maybe my understanding of that is incorrect. > > - Now I am just wondering if we really need the "combo" functionality or not. > > Can we fine tune the DT cpu-cooling properties (existing ones) for a platform, > > so that it automatically acts as a combo cooling device? I am not 100% sure > > its gonna fly, but just wanted to make sure its not possible to work around > > with and then only try the combo device thing. > > > > For example, suppose that with just cpufreq-cooling device we need to take the > > CPU down to 1 GHz from 2 GHz if we cross temperature 'X'. What if we can change > > this policy from DT and say the cpufreq-cooling device goes to 1.5 GHz and > > cpuidle-cooling device takes us to idle for 'y' us, and the effect of > > combination of these two is >= the effect of the 1 GHz for just the > > cpufreq-cooling device. > > > > Is there any possibility of this to work ? > > It does not make sense. The combo does that automatically by computing > the power equivalence more precisely. Sure, but that works by creating a virtual combo-cooling device instead of two separate cooling devices and then there are several limitation (at least right now) where it doesn't sense the real situation automagically. For example I would expect the combo to just work with cpuidle if cpufreq isn't present and as soon as cpufreq comes in, covert itself to cpufreq+cpuidle. I was just trying to present another view at solving the problem at hand, not that one is better than the other. -- viresh