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([2a01:e34:ed2f:f020:5828:300b:5226:ef02]) by smtp.googlemail.com with ESMTPSA id c8sm2615013wmq.34.2022.02.17.10.27.43 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 17 Feb 2022 10:27:45 -0800 (PST) Message-ID: <3651bf48-eb0f-1835-3c5e-1dbdc2730fb4@linaro.org> Date: Thu, 17 Feb 2022 19:27:36 +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: Doug Anderson , Lukasz Luba Cc: Matthias Kaehlcke , 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 , jorcrous@amazon.com, Rob Clark , Manaf Meethalavalappu Pallikunhi 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: 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 Adding Manaf (QCom) in the loop On 17/02/2022 17:37, Doug Anderson wrote: > Hi, > > On Thu, Feb 17, 2022 at 2:47 AM 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]. > > It seems like there _should_ be a way to get the voltage out for GPU > operating points, like is done with cpufreq in > qcom_cpufreq_hw_read_lut(), but it might need someone with Qualcomm > documentation to help with it. Maybe Rajendra would be able to help? > Adding Jordon and Rob to this conversation in case they're aware of > anything. > > As you said, we could just list a power for each frequency, though. > > I'm actually not sure which one would be more accurate across a range > of devices with different "corners": specifying a dynamic power > coefficient used for all "corners" and then using the actual voltage > and doing the math, or specifying a power number for each frequency > and ignoring the actual voltage used. In any case we're trying to get > ballpark numbers and not every device will be exactly the same, so > probably it doesn't matter that much. > > >> 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. 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 > > Matthias: I think you've spent more time on the thermal stuff than me > so I'll assume you'll follow-up here. If not then please yell! > > Ideally, though, someone from Qualcomm would jump in an own this. > Basically it allows more intelligently throttling the GPU and CPU > together in tandem instead of treating them separately IIUC, right? > > -Doug -- Linaro.org │ Open source software for ARM SoCs Follow Linaro: Facebook | Twitter | Blog