[ltp] fan stuck on high - temps appear fine

[Henrique de Moraes Holschuh]

On Sun, 02 Nov 2008, John Li wrote:
> And finally, I've noticed that sometimes when I unplug the laptop and
> run off the battery, the fan slows down. I just discovered this, so

Yes, the EC can (and I bet it does, the X40 and X41 did it in ACPI)
change either the thermal-fan control loop parameters, or the target
RPM speed of each fan level (and likely both) depending on whether you
are discharging or charging a battery.

> I would have imagined the BIOS controlled the fan directly - what sort
> of bug would cause the fan to not slow down, even at sane
> temperatures?

Something wrong with the histeresys in the fan-thermal control loop
parameters.

-- 
  "One disk to rule them all, One disk to find them. One disk to bring
  them all and in the darkness grind them. In the Land of Redmond
  where the shadows lie." -- The Silicon Valley Tarot
  Henrique Holschuh