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([2a01:e34:ed2f:f020:75c3:cda5:890e:8e1b]) by smtp.googlemail.com with ESMTPSA id q20sm1393652wmj.5.2020.09.15.14.23.50 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 15 Sep 2020 14:23:50 -0700 (PDT) Subject: Re: is 'dynamic-power-coefficient' expected to be based on 'real' power measurements? To: Matthias Kaehlcke Cc: Rajendra Nayak , Lukasz Luba , Rob Herring , DTML , Doug Anderson , linux-pm@vger.kernel.org, Amit Daniel Kachhap , Viresh Kumar , Javi Merino References: <248bb01e-1746-c84c-78c4-3cf7d2541a70@codeaurora.org> <20200915172444.GA2771744@google.com> <406d5d4e-d7d7-8a37-5501-119b734facb3@linaro.org> <20200915175808.GB2771744@google.com> <27785351-ba14-dc92-6761-d64962c29596@linaro.org> <20200915211309.GC2771744@google.com> From: Daniel Lezcano Message-ID: <808029c4-3a05-1926-934d-10739190ab9e@linaro.org> Date: Tue, 15 Sep 2020 23:23:49 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: <20200915211309.GC2771744@google.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: linux-pm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-pm@vger.kernel.org On 15/09/2020 23:13, Matthias Kaehlcke wrote: > On Tue, Sep 15, 2020 at 10:55:52PM +0200, Daniel Lezcano wrote: >> On 15/09/2020 19:58, Matthias Kaehlcke wrote: >>> On Tue, Sep 15, 2020 at 07:50:10PM +0200, Daniel Lezcano wrote: >>>> On 15/09/2020 19:24, Matthias Kaehlcke wrote: >>>>> +Thermal folks >>>>> >>>>> Hi Rajendra, >>>>> >>>>> On Tue, Sep 15, 2020 at 11:14:00AM +0530, Rajendra Nayak wrote: >>>>>> Hi Rob, >>>>>> >>>>>> There has been some discussions on another thread [1] around the DPC (dynamic-power-coefficient) values >>>>>> for CPU's being relative vs absolute (based on real power) and should they be used to derive 'real' power >>>>>> at various OPPs in order to calculate things like 'sustainable-power' for thermal zones. >>>>>> I believe relative values work perfectly fine for scheduling decisions, but with others using this for >>>>>> calculating power values in mW, is there a need to document the property as something that *has* to be >>>>>> based on real power measurements? >>>>> >>>>> Relative values may work for scheduling decisions, but not for thermal >>>>> management with the power allocator, at least not when CPU cooling devices >>>>> are combined with others that specify their power consumption in absolute >>>>> values. Such a configuration should be supported IMO. >>>> >>>> The energy model is used in the cpufreq cooling device and if the >>>> sustainable power is consistent with the relative values then there is >>>> no reason it shouldn't work. >>> >>> Agreed on thermal zones that exclusively use CPUs as cooling devices, but >>> what when you have mixed zones, with CPUs with their pseudo-unit and e.g. a >>> GPU that specifies its power in mW? >> >> Well, if a SoC vendor decides to mix the units, then there is nothing we >> can do. >> >> When specifying the power numbers available for the SoC, they could be >> all scaled against the highest power number. > > The GPU was just one example, a device could have heat dissipating components > that are not from the SoC vendor (e.g. WiFi, modem, backlight), and depending > on the design it might not make sense to have separate thermal zones. Is it possible to elaborate, I'm not sure to get the point ? >> There are so many factors on the hardware, the firmware, the kernel and >> the userspace sides having an impact on the energy efficiency, I don't >> understand why SoC vendors are so shy to share the power numbers... > > nor do I, someone could just perform measurements to determine DPCs > with the proper scale if Qualcomm refuses to provide them ... > -- Linaro.org │ Open source software for ARM SoCs Follow Linaro: Facebook | Twitter | Blog