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 -- To unsubscribe from this list: send the line "unsubscribe linux-acpi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
