On 02/02/2018 11:42, Viresh Kumar wrote: > Hi Daniel, Hi Viresh,
> I have gone through the other review comments, specially from Daniel T.. > While I > share some of his concerns, I have few more of mine. > > On 23-01-18, 16:34, Daniel Lezcano wrote: >> +late_initcall(cpu_cooling_init); > > For example, this thing isn't going to fly nicely as you have assumed cpufreq > and cpuidle drivers are going to be part of the kernel itself. What if they > are > modules and are inserted after late-init ? There are more cases like this > where > the cpufreq driver may unregister the cpufreq cooling device on the fly and > then > add it back. And so this stuff is a bit tricky. The cpuidle driver can not be compiled as a module. Agree the cpufreq driver can be unloaded and this part needs some adjustments. > 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. > - 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. -- <http://www.linaro.org/> Linaro.org │ Open source software for ARM SoCs Follow Linaro: <http://www.facebook.com/pages/Linaro> Facebook | <http://twitter.com/#!/linaroorg> Twitter | <http://www.linaro.org/linaro-blog/> Blog
