Messages in this thread | | | Subject | Re: [PATCH 0/4] Add sustainable OPP concept | From | Lukasz Luba <> | Date | Fri, 30 Oct 2020 09:19:48 +0000 |
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On 10/30/20 8:29 AM, Viresh Kumar wrote: > On 29-10-20, 09:56, Lukasz Luba wrote: >> There were discussions about Energy Model (EM), scale of values (mW or >> abstract scale) and relation to EAS and IPA. You can find quite long >> discussion below v2 [1] (there is also v3 send after agreement [2]). >> We have in thermal DT binding: 'sustainable-power' expressed in mW, >> which is used by IPA, but it would not support bogoWatts. > > Why so ? (I am sorry, can't dig into such long threads without knowing > which message I am looking for :( ). Lets assume if that same property > can be used for bogoWatts, will that be sufficient for you ? Or you > will still need this patch set ?
I had a patch for that, but I know Rob's opinion on this one [1] (which is below in that thread).
> >> The sustainable power is used for estimation of internal coefficients >> (also for power budget), which I am trying to change to work with >> 'abstract scale' [3][4]. >> >> This would allow to estimate sustainable power of the system based on >> CPUs, GPU opp-sustainable points, where we don't have >> 'sustainable-power' or devices using bogoWatts. > > Then maybe we should ahve sustainable-power in those cases too instead > of adding a meaningless (IMHO) binding.
How about dropping the DT binding, but just adding this new field into dev_pm_opp? There will be no DT parsing code, just the get/set functions, which will be used in SCMI patch 4/4 and in IPA? That would not require to change any DT bindings.
> > Honestly speaking, as Nishanth said, there is nothing like a > sustainable OPP in reality. Moreover, the DT needs to describe the > hardware as it is (and in some cases the behavior of the firmware). > And what you are trying to add here is none of them and so it should > not go in DT as such. There are too many factors which play a part > here, ambient temperature is one of the biggest ones, and the software > needs to find the sustainable OPP by itself based on the current > situation. > > So I don't really see a good reason why such a property should be > added here.
I see. Just for your information SCMI supports 'Sustained Performance' expressed in kHz.
> > Coming to properties like suspend-opp, it made sense for some of the > platforms as the last configured frequency of the CPU plays a part in > deciding the power consumed by the SoC even when the system is > suspended. And finding an optimal OPP (normally the lowest) there > would make sense and so was that property added. >
I also found that suspend-opp (83f8ca45afbf041e312909). I hope you wouldn't mind if I add this new field into dev_pm_opp (no DT support, just FW).
[1] https://lore.kernel.org/lkml/20201002114426.31277-4-lukasz.luba@arm.com/
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