Re: Using a temperature sensor with 1-bit output for CPU throttling

[Mason <slash.tmp@free.fr>]

On 21/07/2015 11:10, Mason wrote:

> I don't understand this behavior from the governor:
> 
> [   27.557494] thermal thermal_zone0: last_temperature=0, current_temperature=51000
> [   27.583626] thermal thermal_zone0: Trip0[type=1,temp=70000]:trend=1,throttle=0
> [   27.590961] thermal cooling_device0: cur_state=0
> [   27.595672] thermal cooling_device0: old_target=-1, target=-1
> [   27.601473] thermal cooling_device0: zone0->target=4294967295
> [   27.607263] thermal cooling_device0: set to state 0
> 
> [   40.643340] thermal thermal_zone0: last_temperature=51000, current_temperature=46000
> [   40.669930] thermal thermal_zone0: Trip0[type=1,temp=70000]:trend=2,throttle=0
> [   40.677217] thermal cooling_device0: cur_state=0
> [   40.681873] thermal cooling_device0: old_target=-1, target=4
> [   40.687579] thermal cooling_device0: zone0->target=4
> [   40.692669] thermal cooling_device0: set to state 4
> 
> The first temperature read = 51°C (below the 70°C trip point).
> Next read = 46°C (still below the trip point) and even though
> the governor claims throttle=0, it sets the cooling state to 4
> (so minimal frequency if I understand correctly).

Never mind. This is due to a bug that was fixed almost a year ago.
(commit 26bb0e9a1a938ec98ee07aa76533f1a711fba706)

I've requested the fix be back-ported to linux-3.14.y
http://thread.gmane.org/gmane.linux.kernel.stable/143070

Regards.