fan behaviour

fan behaviour

[David Douard]

Hi,
there have been quite a long time since I've played wit ACPI on my Compaq Evo 
N150...
Remember that I nedd a pached DSDT to get many things to work (bat, processor 
C states etc.).

I used to have pb with fans : they where not autmatically turned on/off 
according to CPU temperature. Thus I made a little daemon to hold that.
But then I tried a nex ACPI version (one month or two ago), and I realized 
that fan where handled fine. But this was with the original DSDT.
I recompiled the kernel with my DSDT. And then fans where not handled.

So I compiled the lates acpi patch on a 2.4.20. And I realized that I can make 
automatic fan handling if I play with the 
/proc/acpi/thermal_zone/THRM/cooling_mode.
The things I have to do so are quite esoteric : set passive cooling mode, make 
cpu hot (reach the trip point); then set active cooling mode. (well I guess 
the manipulation is that, I'm not very sure).
Then, the fans are nicely handled.

This sound very strange to me, and my question is this : does anyone have any 
idea on if that may come from ACPI CA (the AML interpreter maybe), or from 
the DSDT code which (I know) is bugged.

Note too another strange thing (I made it twice) :
I set (in single user mode) the cooling mode to passive and then lauch a 
little cpuburner program. Throttling started to increase while temperature 
reach the passive trip point (this is the first time I see throttling 
working. It used to hang the machine if I try to change its value). 
But when I killed  the cpuburner process, it hanged the machine !

Thanks for any tip !
	David Douard



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