Set minimum fan speed on Fujitsu/Kontron motherboards with Teutates BMC

min_duty_cycle_settei.sh

#!/bin/bash

# Copyright (C) 2020 Kia
# Licensed under Zero Clause BSD License
# Copy of original Gist from https://gist.github.com/superbaud/651d898b3958be552e8d3c403c988fad


if [[ $# -ne 3 ]]; then
    echo "usage: $0 (BMC I2C BUS NUMBER) (FAN PAGE) (DUTY CYCLE FLOOR)"
    echo ""
    echo "BMC I2C BUS NUMBER can be found as follows"
    echo "$ ls /sys/bus/i2c/devices/*/hwmon/hwmon*/fan1_input"
    echo ""
    echo "if the output of that command is:"
    echo "/sys/bus/i2c/devices/7-0073/hwmon/hwmon4/fan1_input"
    echo "that means that the I2C bus number is 7"
    echo "Check /sys/module/ftsteutates/drivers/i2c\:ftsteutates/ to be sure"
    echo ""
    echo "FAN PAGE = 0x48 + index of fan"
    echo "On my system, FAN PAGE can be (0x48, 0x49, 0x4a, 0x4b)"
    echo ""
    echo "DUTY CYCLE FLOOR can be any number from 0 to 255, but please"
    echo "don't set it lower than it already is."
    echo ""
    echo "This tool asks the Teutates BMC (in a way that does not survive"
    echo "reboots/power-cycles/shutdowns) to keep the PWM waveform that is"
    echo "fed to the fan corresponding to FAN PAGE to have a duty cycle that"
    echo "is greater or equal to (DUTY CYCLE FLOOR) / 255"
    echo ""
    echo "A fan that runs at MAX_RPM without a PWM signal (or with a DC PWM"
    echo "signal) will never run slower than MAX_RPM * (DUTY CYCLE FLOOR) / 255"
    echo ""
    echo "#########################################################################"
    echo "                               ☢CAUTION!!☢"
    echo "The supplied I2C bus number MUST correspond to the bus where the"
    echo "Teutates BMC lives on."
    echo ""
    echo "The supplied fan page must be between 0x48-0x4f inclusive and"
    echo "must correspond to a fan in your system connected to the Teutates BMC."
    echo ""
    echo "Incorrectly specifying the I2C bus number or fan page may BRICK"
    echo "or IRREVERSIBLY DESTROY your system!"
    echo "                               ☢CAUTION!!☢"
    echo "#########################################################################"
    echo ""
    echo "It is likely that this tool will not produce expected results if"
    echo "SilentFanConfig-Manager has been run -- which writes fan config stuff"
    echo "into nonvolatile storage. The aforementioned fan config stuff might"
    echo "set a different set of control modes, causing the write to 0x86 to"
    echo "not have the desired effect. I don't have the full Teutates"
    echo "documentation, so i do not know any of the control laws are."
    echo ""
    echo "However, if you have access to SilentFanConfig-Manager, why do you even"
    echo "need this?"
    echo ""
    echo "This tool has only been tested on a single motherboard:"
    echo "FUJITSU /D3641-S1, BIOS V5.0.0.13 R1.7.0 for D3641-S1x"
    echo "with FTS Teutates chip revision: 3.11"
    echo ""
    echo "FOR USE ONLY ON FUJITSU/KONTRON MOTHERBOARDS WITH TEUTATES BMC"
    echo ""
    exit 1
fi



case $2 in
    0x48|0x49|0x4a|0x4b|0x4c|0x4d|0x4e|0x4f)
        echo "supplied fan page is "$2
        ;;
    *)
        echo "INVALID FAN PAGE!!"
        exit 2
        ;;
esac




set -e

echo -n "Testing for Teutates BMC presence... "
# test that we have a teutates bmc, ideally this modprobe fails otherwise
sudo modprobe ftsteutates
# but we need it not be loaded, so we can have the i2c bus to ourselves
sudo rmmod ftsteutates

echo "present"
# this lets us do i2cset
sudo modprobe i2c-dev

# switch the page for the fan in question. the user is responsible
# for making sure this is between 0x48 and 0x4f
echo "writing to the i2c bus; hope you gave us the correct one!"
sudo i2cset -y $1 0x73 0x7f $2

# set PWM duty cycle
sudo i2cset -y $1 0x73 0x86 $3

# set the page back to 0x00 just to be kind to whoever (the kernel module) talks with the BMC after us
sudo i2cset -y $1 0x73 0x7f 0x00

echo "writes done"
# let us look at our handiwork via sensors(1).
# be patient, i think the BMC only updates RPM every second or so
sudo modprobe ftsteutates