Messages in this thread | | | Subject | Re: [PATCH 8/8] thermal/drivers/cpu_cooling: Add the combo cpu cooling device | From | Daniel Lezcano <> | Date | Fri, 2 Feb 2018 15:30:10 +0100 |
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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.
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