Messages in this thread |  | | Date | Mon, 5 Feb 2018 09:47:34 +0530 | From | Viresh Kumar <> | Subject | Re: [PATCH 8/8] thermal/drivers/cpu_cooling: Add the combo cpu cooling device |
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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
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