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
