Customizing fan behaviour (temperatures)

Customizing fan behaviour (temperatures)

[Lucas Levrel]

Hi,

I would like to adjust the temperature at which the fan starts, because as 
it is now it runs continuously, at low speed but this continuous noise 
bothers me. I'd rather have it spin faster and intermittently. This is an 
HP laptop.

I've read much (mostly Q&A pages and list threads, regular documentation 
seems to be scarce), and investigated the behaviour of files in 
/sys/devices/virtual/thermal . From what I understand there's no bug, just 
the temperature thresholds are not to my taste.

More specifically, there are 7 cooling_device's (4 of type Fan, 2 
Processor, 1 LCD) and 5 thermal_zone's (the first 4 really are 
temperatures, the last is the fan speed). thermal_zone0 controls the fan. 
The lowest trip_point_?_temp (?==4) is 45000, which is very low. 
Basically, after a few minutes of idle operation temp reaches 50000 or 
55000 (looks like there is 5 °C granularity) and never gets lower: I've 
tried and manually set the fan to speed 2 (echo 1 > 
cooling_device2/cur_state), even then temp doesn't decrease below 50000.

trip_point_?_temp are not writable. I've set thermal.act=60000 in the 
kernel command line, to no avail; is this supposed to be reflected in the 
trip_point_?_temp files? (Note: trip_point_[1-4]_type is "active".) This 
is kernel 3.2.71 .

What can you advise me to do now?

And by the way, for my education:
- how are the trip_point values determined?
- how is hysteresis implemented? I mean, you don't want your fan speed to 
change every other second, so the "speed up" threshold has to be higher 
than the "speed down" one. In fact, I've found no explanation of how the 
trip_point values are used.

Thanks.

-- 
Lucas Levrel
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Re: Customizing fan behaviour (temperatures)

[Lucas Levrel]

Le 13 juillet 2016, Lucas Levrel a écrit :

> Hi,
>
> I would like to adjust the temperature at which the fan starts, because as it 
> is now it runs continuously, at low speed but this continuous noise bothers 
> me. I'd rather have it spin faster and intermittently. This is an HP laptop.
>
> I've read much (mostly Q&A pages and list threads, regular documentation 
> seems to be scarce), and investigated the behaviour of files in 
> /sys/devices/virtual/thermal . From what I understand there's no bug, just 
> the temperature thresholds are not to my taste.
>
> More specifically, there are 7 cooling_device's (4 of type Fan, 2 Processor, 
> 1 LCD) and 5 thermal_zone's (the first 4 really are temperatures, the last is 
> the fan speed). thermal_zone0 controls the fan. The lowest trip_point_?_temp 
> (?==4) is 45000, which is very low. Basically, after a few minutes of idle 
> operation temp reaches 50000 or 55000 (looks like there is 5 °C granularity) 
> and never gets lower: I've tried and manually set the fan to speed 2 (echo 1 
>> cooling_device2/cur_state), even then temp doesn't decrease below 50000.
>
> trip_point_?_temp are not writable. I've set thermal.act=60000 in the kernel 
> command line, to no avail; is this supposed to be reflected in the 
> trip_point_?_temp files? (Note: trip_point_[1-4]_type is "active".) This is 
> kernel 3.2.71 .
>
> What can you advise me to do now?
>
> And by the way, for my education:
> - how are the trip_point values determined?
> - how is hysteresis implemented? I mean, you don't want your fan speed to 
> change every other second, so the "speed up" threshold has to be higher than 
> the "speed down" one. In fact, I've found no explanation of how the 
> trip_point values are used.
>
> Thanks.

Hi again,

After investigating some more, I found how hysteresis works: the 
trip_point_?_temp changes when it is crossed. In my case, 
trip_point_4_temp is 50000 at first (by default), and goes down to 45000 
when the fan starts.

This is also why I saw no effect of thermal.act=60000 last time I tested: 
during boot the temperature reaches this threshold, and trip_point_4_temp 
is set to 45000.

I remain with the following questions:
- how are the trip_point values determined?
- is there a way to set them to taste? More specifically, I would like to 
rise the "fan stop" trigger temp; thermal.act= visibly didn't change 
this...

Thanks again.

-- 
Lucas Levrel
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