Re: [lm-sensors] Fintek f71882fg ACPI conflict

[Guenter Roeck <linux@roeck-us.net>]

On Thu, Jun 28, 2012 at 12:31:30PM +0100, Michael Zintakis wrote:
> 
> >Do you mean sysfs ?
> Yeah, sorry. Everything under /sys/class/hwmon/...
> 
> >Correct. 1 is too low, though. Default value per datasheet is 0x80.
> >Whatever it is, it should be high enough for the fans to start spinning.
> That won't be enough! I did a bit of experimenting and discovered
> the following:
> 
> The minimum value for pwm on all fans necessary to keep them going
> is 75 (decimal) - below that value the fan just stops. The minimum
> value to kick-start the fan and make it spin from standstill is 190
> (also decimal) - nothing below this value is sufficient to move the
> fan from its standstill position (in my script I use the maximum
> value - 255 - to be on the safe side).
> 
> So, even if I set the pwmX_auto_point5_pwm to 75 that won't be
> enough to kick-start the fan initially. On the other hand, if I set
> it to 190 that would be enough, but the fan will continue to spin at
> this rate which is very high (I may as well abandon fan/temperature
> management then).
> 
> >The F71882FG does not have a register to set a "start spinning" pwm value,
> >so your minimum must guarantee that the fans do start to spin.
> >
> >What is your setting for pwmX_enable ? It should probably be set to
> >automatic(2) so the chip can automatically control the fan speed depending
> >on the temperature.
> It is indeed set to 2.
> 
> >>Even if I bring this value to some "idle" current, that won't help
> >>much because when I first boot the system, the fans are *always*
> >>still, so even if the idle state is >1, that won't help me much, so
> >>there must be another - better - way than using a script to
> >>"kickstart" the fans initially, surely!
> >>
> >Maybe fan control is not set to automatic by the BIOS ?
> It is and it is why I am keeping this automatic BIOS fan management
> in place and my script only intervenes to kick-start the fans when
> they are still, otherwise this automatic control is doing a good
> job. The problem is the actual kick-start (and the fact that there
> is no way I could force ACPI to abandon the region of memory used by
> the driver).

That isn't BIOS fan management - it is completely handled by the chip itself.
Problem is most likely that the BIOS does not "kick-start" the fan(s),
and the chip does not have a register to set a "start fan" pwm value (other
chips such as the NCT677X do have a register for that purpose). So you may
be stuck with your manual method if you want to keep the fan running at speeds
lower than pwm=190. Another option might be to find a fan which starts at lower
pwm values, and/or does not need to be kick-started.

Guenter