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([2a01:e34:ed2f:f020:6165:d98a:b553:c3c1]) by smtp.googlemail.com with ESMTPSA id g20sm1210307wmq.17.2022.02.17.03.28.31 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 17 Feb 2022 03:28:33 -0800 (PST) Message-ID: <53bc13ca-998f-ff83-d9f7-9a83d35b24fd@linaro.org> Date: Thu, 17 Feb 2022 12:28:31 +0100 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.5.0 Subject: Re: [PATCH 1/2] thermal: cooling: Check Energy Model type in cpufreq_cooling and devfreq_cooling Content-Language: en-US To: Lukasz Luba , Doug Anderson , Matthias Kaehlcke Cc: LKML , Linux PM , amit daniel kachhap , Viresh Kumar , "Rafael J. Wysocki" , Amit Kucheria , Zhang Rui , Dietmar Eggemann , Pierre.Gondois@arm.com, Stephen Boyd , Rajendra Nayak , Bjorn Andersson References: <20220207073036.14901-1-lukasz.luba@arm.com> <20220207073036.14901-2-lukasz.luba@arm.com> <4a7d4e94-1461-5bac-5798-29998af9793a@arm.com> <7c059f4f-7439-0cad-c398-96dbde4e49c1@linaro.org> <5b8ca53e-3595-85fd-5ae9-a5e8285e8513@arm.com> From: Daniel Lezcano In-Reply-To: <5b8ca53e-3595-85fd-5ae9-a5e8285e8513@arm.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 17/02/2022 11:47, Lukasz Luba wrote: > Hi Daniel, > > On 2/17/22 10:10 AM, Daniel Lezcano wrote: >> On 16/02/2022 18:33, Doug Anderson wrote: >>> Hi, >>> >>> On Wed, Feb 16, 2022 at 7:35 AM Lukasz Luba wrote: >>>> >>>> Hi Matthias, >>>> >>>> On 2/9/22 10:17 PM, Matthias Kaehlcke wrote: >>>>> On Wed, Feb 09, 2022 at 11:16:36AM +0000, Lukasz Luba wrote: >>>>>> >>>>>> >>>>>> On 2/8/22 5:25 PM, Matthias Kaehlcke wrote: >>>>>>> On Tue, Feb 08, 2022 at 09:32:28AM +0000, Lukasz Luba wrote: >>>>>>>> >>>>>>>> >>>> >>>> [snip] >>>> >>>>>>>> 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] >>>>>> >>>>>> Thank you Matthias. I will investigate your setup to get better >>>>>> understanding. >>>>> >>>>> Thanks! >>>>> >>>> >>>> I've checked those DT files and related code. >>>> As you already said, this patch is safe for them. >>>> So we can apply it IMO. >>>> >>>> >>>> -------------Off-topic------------------ >>>> Not in $subject comments: >>>> >>>> AFAICS based on two files which define thermal zones: >>>> sc7180-trogdor-homestar.dtsi >>>> sc7180-trogdor-coachz.dtsi >>>> >>>> only the 'big' cores are used as cooling devices in the >>>> 'skin_temp_thermal' - the CPU6 and CPU7. >>>> >>>> I assume you don't want to model at all the power usage >>>> from the Little cluster (which is quite big: 6 CPUs), do you? >>>> I can see that the Little CPUs have small dyn-power-coeff >>>> ~30% of the big and lower max freq, but still might be worth >>>> to add them to IPA. You might give them more 'weight', to >>>> make sure they receive more power during power split. >>>> >>>> You also don't have GPU cooling device in that thermal zone. >>>> Based on my experience if your GPU is a power hungry one, >>>> e.g. 2-4Watts, you might get better results when you model >>>> this 'hot' device (which impacts your temp sensor reported value). >>> >>> I think the two boards you point at (homestar and coachz) are just the >>> two that override the default defined in the SoC dtsi file. If you >>> look in sc7180.dtsi you'll see 'gpuss1-thermal' which has a cooling >>> map. You can also see the cooling maps for the littles. >>> >>> I guess we don't have a `dynamic-power-coefficient` for the GPU, >>> though? Seems like we should, but I haven't dug through all the code >>> here... >> >> The dynamic-power-coefficient is available for OPPs which includes >> CPUfreq and devfreq. As the GPU is managed by devfreq, setting the >> dynamic-power-coefficient makes the energy model available for it. >> >> However, the OPPs must define the frequency and the voltage. That is >> the case for most platforms except on QCom platform. >> >> That may not be specified as it uses a frequency index and the >> hardware does the voltage change in our back. The QCom cpufreq backend >> get the voltage table from a register (or whatever) and completes the >> voltage values for the OPPs, thus adding the information which is >> missing in the device tree. The energy model can then initializes >> itself and allows the usage of the Energy Aware Scheduler. >> >> However this piece of code is missing for the GPU part. >> > > Thank you for joining the discussion. I don't know about that Qcom > GPU voltage information is missing. > > If the voltage is not available (only the frequencies), there is > another way. There is an 'advanced' EM which uses registration function: > em_dev_register_perf_domain(). It uses a local driver callback to get > power for each found frequency. It has benefit because there is no > restriction to 'fit' into the math formula, instead just avg power > values can be feed into EM. It's called 'advanced' EM [1]. > > Now we hit (again) the DT & EM issue (it's an old one, IIRC Morten > was proposing from ~2014 this upstream, but EAS wasn't merged back > then): > where to store these power-freq values, which are then used by the > callback. Why not make it more generic and replace the frequency by a performance index, so it can be used by any kind of perf limiter? > We have the 'dynamic-power-coefficient' in DT, but > it has limitations. It would be good to have this simple array > attached to the GPU/CPU node. IMHO it meet the requirement of DT, > it describes the HW (it would have HZ and Watts values). > > Doug, Matthias could you have a look at that function and its > usage, please [1]? > If you guys would support me in this, I would start, with an RFC > proposal, a discussion on LKML. > > > [1] > https://elixir.bootlin.com/linux/v5.17-rc4/source/Documentation/power/energy-model.rst#L87 > -- Linaro.org │ Open source software for ARM SoCs Follow Linaro: Facebook | Twitter | Blog