Fan speed control

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Fancontrol, part of lm_sensors, can be used to control the speed and sound of CPU/case fans. This article covers configuration/setup of the utility.

Sensor driver

Support for newer motherboards may not yet be in the Linux kernel. Check the official lm-sensors devices table to see if experimental drivers are available for such motherboards.

It is recommended not to use lm_sensors.service to load the needed modules for fancontrol. Instead, manually place them in /etc/modules-load.d/load_these.conf since the order in which these modules are loaded dictate the order in which the needed symlinks for hwmon get created. In other words, using the lm_sensors.service causes inconsistencies boot-to-boot which will render the configuration file for fan control worthless for a consistency point of view. To avoid this problem:

In /etc/conf.d/lm_sensors you find the modules. If not there, run as root sensors-detect accepting the defaults. In the modules-load.d file place one module name per line. Specifying them like this will create a reproducible order. Another alternative is to use absolute device names in the configuration file.[1]

lm-sensors

Set up lm_sensors.

$ sensors
coretemp-isa-0000
Adapter: ISA adapter
Core 0:      +29.0°C  (high = +76.0°C, crit = +100.0°C)  

[...]

it8718-isa-0290
Adapter: ISA adapter
Vcc:         +1.14 V  (min =  +0.00 V, max =  +4.08 V)   
VTT:         +2.08 V  (min =  +0.00 V, max =  +4.08 V)   
+3.3V:       +3.33 V  (min =  +0.00 V, max =  +4.08 V)   
NB Vcore:    +0.03 V  (min =  +0.00 V, max =  +4.08 V)   
VDRAM:       +2.13 V  (min =  +0.00 V, max =  +4.08 V)   
fan1:        690 RPM  (min =   10 RPM)
temp1:       +37.5°C  (low  = +129.5°C, high = +129.5°C)  sensor = thermistor
temp2:       +25.0°C  (low  = +127.0°C, high = +127.0°C)  sensor = thermal diode

If the output does not display an RPM value for the CPU fan, one may need to increase the fan divisor. If fan speed is shown and higher than 0, skip the next step.

Increasing fan_div

The first line of the sensors output is the chipset used by the motherboard for readings of temperatures and voltages.

Create a file in /etc/sensors.d/:

/etc/sensors.d/fan-speed-control.conf
chip "coretemp-isa-*"
set fanX_div 4

Replacing coretemp-isa- with name of the chipset and X with the number of the CPU fan to change.

Save the file, and run as root:

# sensors -s

which will reload the configuration files.

Run sensors again, and check if there is an RPM readout. If not, increase the divisor to 8, 16, or 32. YMMV!

Configuration

Note: Advanced users may want to skip this section and write /etc/fancontrol on their own, which also saves them from hearing all of the fans at full speed.

Once sensors is properly configured, run pwmconfig to test and configure speed control. Follow the instructions in pwmconfig to set up basic speeds. The default configuration options should create a new file, /etc/fancontrol.

Tweaking

Warning: Some of the steps outlined below describe how to tweak fan speeds. Before doing this be sure to have a low CPU load.
Note: On several systems, the included script may report errors as it trys to calibrate fans to the respective PWM. Users may safely ignore these errors. The problem is that the script does not wait long enough before ramping up or down the PWM.

Users wishing more more control may need to tweak the generated configuration. Here is a sample configuration file:

INTERVAL=10
DEVPATH=hwmon0=devices/platform/coretemp.0 hwmon2=devices/platform/w83627ehf.656
DEVNAME=hwmon0=coretemp hwmon2=w83627dhg
FCTEMPS=hwmon0/device/pwm1=hwmon0/device/temp1_input
FCFANS= hwmon0/device/pwm1=hwmon0/device/fan1_input
MINTEMP=hwmon0/device/pwm1=20
MAXTEMP=hwmon0/device/pwm1=55
MINSTART=hwmon0/device/pwm1=150
MINSTOP=hwmon0/device/pwm1=105
  • INTERVAL: how often the daemon should poll CPU temps and adjust fan speeds. INTERVAL is in seconds.

The rest of the configuration file is split into (at least) two values per configuration option. Each configuration option first points to a PWM device which is written to which sets the fan speed. The second "field" is the actual value to set. This allows monitoring and controlling multiple fans and temperatures.

  • FCTEMPS: The temperature input device to read for CPU temperature. The above example corresponds to /sys/class/hwmon/hwmon0/device/temp1_input.
  • FCFANS: The current fan speed, which can be read (like the temperature) in /sys/class/hwmon/hwmon0/device/fan1_input
  • MINTEMP: The temperature (°C) at which to SHUT OFF the CPU fan. Efficient CPUs often will not need a fan while idling. Be sure to set this to a temperature that you know is safe. Setting this to 0 is not recommended and may ruin your hardware!
  • MAXTEMP: The temperature (°C) at which to spin the fan at its MAXIMUM speed. This should be probably be set to perhaps 10 or 20 degrees (°C) below your CPU's critical/shutdown temperature. Setting it closer to MINTEMP will result in higher fan speeds overall.
  • MINSTOP: The PWM value at which your fan stops spinning. Each fan is a little different. Power tweakers can echo different values (between 0 and 255) to /sys/class/hwmon/hwmon0/device/pwm1 and then watch the CPU fan. When the CPU fan stops, use this value.
  • MINSTART: The PWM value at which your fan starts to spin again. This is often a higher value than MINSTOP as more voltage is required to overcome inertia.

There are also two settings fancontrol needs to verify the configuration file is still up to date. The lines start with the setting name and a equality sign, followed by groups of hwmon-class-device=setting, seperated by spaces. You need to specify each setting for each hwmon class device you use anywhere in the config, or fancontrol will not work.

  • DEVPATH: Sets the physical device. You can determine this by executing the command
readlink -f /sys/class/hwmon/hwmon-device/device | sed -e 's/^\/sys\///'
  • DEVNAME: Sets the name of the device. Try:
$ sed -e 's/[[:space:]=]/_/g' /sys/class/hwmon/hwmon-device/device/name
Tip: Use MAXPWM and MINPWM options that limit fan speed range. See fancontrol manual page for details.
Tip: Not only the DEVPATH may change on reboot due to different timing of module loading, but also e.g. the temperature sensor paths (hwmon0/device/temp1_input becomes hwmon0/temp1_input). This usually happens on a kernel update. Check the system log to find out which is the troublemaker:
# systemctl status fancontrol.service
and correct your config file accordingly.

fancontrol

Try to run fancontrol:

# /usr/bin/fancontrol

A properly configured setup will not error out and will take control of system fans. Users should hear system fans slowing shortly after executing this command.

Note: For Dell Latitude/Inspiron laptops, i8kutilsAUR is available. The i8k kernel module is known to have issues on several models.

To make fancontrol start automatically on every boot, enable fancontrol.service.

For the i8kmon service to be capable of controlling the fan, the auto config option needs to be set to 1 in /etc/i8kutils/i8kmon.conf.

Note: Upon upgrading/changing the kernel, running fancontrol may result in an error regarding changed device paths. This issue may be fixed by running sensors-detect and restarting the system.