Python script to edit the X8DTL-iF Registry to control fan speed.

README.md

smx8fancontrol on unraid

To change the fan speeds on a SuperMicro X8 board (I have X8DTL-iF) there's a tool smx8fancontrol

Now there's a few deps that are needed and it's a pain to install them on UnRaid. So far this has been my script to get it to run:

# https://www.ikus-soft.com/en/blog/2017-10-01-supermicro-x8-controle-ventilateur/
# install smx8fancontrol on unraid
# install nerd-pack and enable `python3` and `pip`

# install smbus2
pip install smbus2

# get the script
# Optimized version from timemaster67
# See also https://forums.servethehome.com/index.php?threads/supermicro-ipmi-fan-control.12025/#post-167086
sudo wget -O /usr/local/bin/smx8fancontrol \
https://gist.githubusercontent.com/alber70g/00f2d87c0db78a3c51db28cc670e261a/raw/smx8fancontrol

sudo wget -O /usr/local/bin/smx8fancontrolif \
https://gist.githubusercontent.com/alber70g/00f2d87c0db78a3c51db28cc670e261a/raw/smx8fancontrolif

# make it executable
chmod +x /usr/local/bin/smx8fancontrol 

# trigger i2c module
modprobe -r w83795
modprobe i2c-dev

# run it
smx8fancontrol -s

wait 5

# change to smart
smx8fancontrolif -m smart -p 01,05,10,20,40,80 -t 25,30,40,50,60,70 -H 2

wait 5

# set tresholds to not get errors in IPMI
# https://www.truenas.com/community/threads/how-to-change-ipmi-sensor-thresholds-using-ipmitool.53620/page-6
# I have the X8DTL-iF and these are squared. So 10 means 10*10 = 100rpm
ipmitool sensor thresh "FAN 1" lower 10 21 29
wait 2
ipmitool sensor thresh "FAN 2" lower 10 21 29
wait 2
ipmitool sensor thresh "FAN 3" lower 10 21 29
wait 2
ipmitool sensor thresh "FAN 4" lower 10 21 29
wait 2
ipmitool sensor thresh "FAN 1" upper 175 178 181
wait 2
ipmitool sensor thresh "FAN 2" upper 175 178 181
wait 2
ipmitool sensor thresh "FAN 3" upper 175 178 181
wait 2
ipmitool sensor thresh "FAN 4" upper 175 178 181
wait 2

# reset IPMI user ADMIN
#ipmitool -I open user set password 2 ADMIN

smx8fancontrol

#!/usr/bin/env python3
#
# To use to READ the sensors and table
# 
#######################
# smx8fancontrol -s
#######################
#
# Licensed to the Apache Software Foundation (ASF) under one
# or more contributor license agreements.  See the NOTICE file
# distributed with this work for additional information
# regarding copyright ownership.  The ASF licenses this file
# to you under the Apache License, Version 2.0 (the
# "License"); you may not use this file except in compliance
# with the License.  You may obtain a copy of the License at
# 
#   http://www.apache.org/licenses/LICENSE-2.0
# 
# Unless required by applicable law or agreed to in writing,
# software distributed under the License is distributed on an
# "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
# KIND, either express or implied.  See the License for the
# specific language governing permissions and limitations
# under the License.

import sys
import argparse
from smbus2 import SMBus
from contextlib import contextmanager

# 
# All register ceom from
# https://github.com/torvalds/linux/blob/5924bbecd0267d87c24110cbe2041b5075173a25/drivers/hwmon/w83795.c
#

#chip i2c address to use
ADDRESS=0x2f

NUVOTON_VENDOR_ID = 0x5ca3
CHIP_ID = 0x79

W83795_REG_VENDOR_ID = 0X0FD
W83795_REG_CHIP_ID = 0X0FE

#the registery is banked. To access the full data, user must switch the bank, like a page, in this register. 
#when this register lower 2 bit are set, the rest of the data change according to it. 
#bank0 show sensors related config bank 1 show nothing interesting bank 2 show fan related config. bank 3 show peci related config
W83795_REG_BANKSEL = 0x00

# Fan Control Mode Selection Registers (FCMS)
W83795_REG_FCMS1 = 0x201
W83795_REG_FCMS2 = 0x208

#Temperature to Fan mapping Relationships Register (TFMR)
#W83795_REG_TFMR = lambda index: 0x202 + index
#There is 6 temperature source thus 6 entry, Each entry contains a binary representation of if one of the 8 pwm is linked to that temperature
W83795_REG_TFMR = lambda index: 0x202 + index

#Temperature Source Selection Register (TSS)
#data for pwm1 and 2 are mixed in the first byte, pwm3 and 4, second...
W83795_REG_TSS = lambda index: 0x209 + floor((index/2))

#Default Fan Speed at Power-on (DFSP)
W83795_REG_DFSP = 0x20c

#the range is used to access all element from 0x80 to 0xde without declaring everything. 
#temp1 is index 0, thus 0 * 0x10 is 0. we access 0x80 to 0x87 straight. 
#temp3 is index 1, thus 1* 0x10 is 0x10, so we access 0x80 + 0x10 = 0x9x to 0x96
W83795_REG_SFIV_TEMP = lambda index: range(0x280 + index * 0x10, 0x280 + index * 0x10 + 6)
W83795_REG_SFIV_DCPWM = lambda index: range(0x288 + index * 0x10, 0x288 + index * 0x10 + 6)

#Fan Output Value (FOV)
W83795_REG_FOV = lambda index: 0x210 + index

#Fan Output Nonstop Value (FONV)
W83795_REG_FONV = lambda index: 0x228 + index

#Fan Output Stop Time (FOST)
W83795_REG_FOST = lambda index: 0x230 + index

#SmartFan Output Step Up Time (SFOSUT)
W83795_REG_SFOSUT = 0x20D

#SmartFan Output Step Down Time (SFOSDT)
W83795_REG_SFOSDT = 0x20E

#Target Temperature of Temperature Inputs (TTTI)
W83795_REG_TTTI = lambda index: 0x260 + index

#Critical Temperature to Full Speed all fan (CTFS)
W83795_REG_CTFS = lambda index: 0x268 + index

#Hystersis of Temperature (HT)
W83795_REG_HT = lambda index: 0x270 + index


#not in use
#Fan Output PWM Frequency Prescalar (FOPFP)
W83795_REG_FOPFP = lambda index: 0x218 + index



@contextmanager
def bank(bus, value):
	prev_value = w83795_set_bank(bus, value)
	yield
	w83795_set_bank(bus, prev_value)


def w83795_set_bank(bus, bank):
	assert bank in [0,1,2,3]
	# Read current bank value, ignoring reserved bit and high byte access fields.
	field = bus.read_byte_data(ADDRESS, W83795_REG_BANKSEL)
	cur_bank = field & 0b00000011
	# If the bank is already set, nothing to do
	if cur_bank == bank:
		return cur_bank
	# Change the bank, preserving reserved value
	bus.write_byte_data(ADDRESS, W83795_REG_BANKSEL, field | bank )
	# Return previous bank value
	return cur_bank


def w83795_write(bus, reg, value):
	"""
	Write into the given registry.
	"""
	with bank(bus, reg >> 8):
		return bus.write_byte_data(ADDRESS, reg & 0xff, value & 0xff)


def w83795_read(bus, reg):
	"""
	Read the given registry.
	"""
	
	if hasattr(reg, '__iter__'):
			with bank(bus, reg[0] >> 8):
				return map(lambda r: bus.read_byte_data(ADDRESS, r & 0xff), reg)
	with bank(bus, reg >> 8):
		return bus.read_byte_data(ADDRESS, reg & 0xff)


def CheckChipset(bus):
	
	#Check that we are dealing with the W83795 chipset
	
	#set the register to get the high bit value, while keeping the reserved bit and the bank intact
	multidata = w83795_read(bus, W83795_REG_BANKSEL)
	w83795_write(bus, W83795_REG_BANKSEL, (multidata & 0b01111111) | 0b10000000)
		
	#get the high bit value
	vendor = w83795_read(bus, W83795_REG_VENDOR_ID)
	
	
	#shift vendor part to the left
	vendor = vendor << 8
	
	#set the register to get the low bit value, while keeping the reserved bit and the bank intact
	w83795_write(bus, W83795_REG_BANKSEL, multidata & 0b01111111)
	vendor = vendor | w83795_read(bus, W83795_REG_VENDOR_ID)

	chipid = w83795_read(bus, W83795_REG_CHIP_ID)
	#debug("vendor %s, chipid %s" % (vendor, chipid))
	if vendor != NUVOTON_VENDOR_ID or chipid != CHIP_ID:
		print("unexpected vendor %s, chipid %s" % (vendor, chipid))
		return False
	return True





def ShowInfo(bus):
	#get fan configuration
	fcms1 = w83795_read(bus, W83795_REG_FCMS1)
	fcms2 = w83795_read(bus, W83795_REG_FCMS2) & 0b00111111
	
	
	#get the Temperature to Fan mapping Relationships Register (TFMR) and keep a cache for multiple reuse
	tfmr = []
	for t in range(0,6):
		tfmr.append(w83795_read(bus, W83795_REG_TFMR(t)))
	

	for f in range(0,6):
		#for each controllable pwm
		print("Fan%s" % (f+1))
		
		#binary fan value, used for binary and
		#shift number binary 00000001 f bytes to the left, 
		#00000001 shifted 1 time to the left equals 00000010. 
		fbin = 1 << f
		#show the calculated binary number
		#print(fbin)
		
		# get the operating mode of the fan (manual, speed cruise, thermal cruise, smart fan)

		#Check the mode of the fan by looking at the 
		#print(fcms1 & fbin)
		#print(fcms2 & fbin)
		isSpeedCruise = fcms1 & fbin
		
		#wrong wrong wrong. fcms2 affiche les ttemps, pas les fans. !!  8 fans, 6 temp!! il faut checker les temps to fans relationship, 
		#ensuite checker le mode des temps.
		isThermalCruise = not isSpeedCruise and not(fcms2 & fbin)
		isSmartFan = not isSpeedCruise and (fcms2 & fbin)
		tempToFanMapping = []
				
		#Check if the fan is in manual mode
		
		if (not isSpeedCruise):
			#if the fan is marked not in speed cruise but there is no temp relationship to this fan, it's in manual mode
			
			hasAtLeastOneRelationship = False
			
			#there is 6 different temperature
			for t in range(0,6):
				
				#check if the current fan (fbin) has a relationship with any of the 6 temperature
				if (tfmr[t] & fbin > 0):
					hasAtLeastOneRelationship = True
					#save the temperature sensor related to this fan
					tempToFanMapping.append("Temp %s" % t)
					
				
			if (not hasAtLeastOneRelationship):
				isSmartFan = False
				isThermalCruise = False			
		
		
		if isSpeedCruise:
			print("  Mode : Speed Cruise mode")
		elif isThermalCruise:
			print("  Mode : Thermal Cruise mode")
		elif isSmartFan:
			print("  Mode : Smart Fan mode")
		else:
			print("  Mode : Manual mode")
			
				
		pwm = w83795_read(bus, W83795_REG_FOV(f))
		print("  Fan Output Value (FOV): %s%%" % round(to_perc(pwm), 2))
		
		if isSmartFan:
			
			print("  Temperature to Fan mapping Relationships Register (TFMR): fan linked to : %s" % ",".join(tempToFanMapping))

			
			
			#not sure if useful
			#print("  Temperature Source Selection Register (TSS)")
			#temp = w83795_read(bus, W83795_REG_TSS(f))
			
			
			
			print("  Smart Fan Control Table (SFIV)")
			temp = w83795_read(bus, W83795_REG_SFIV_TEMP(f))
			print(''.join([("%dC" % to_degree(v)).rjust(6) for v in temp]))

			dcpwm = w83795_read(bus, W83795_REG_SFIV_DCPWM(f))
			print(''.join([("%d%%" % to_perc(v)).rjust(6) for v in dcpwm]))
			print('')
		
		if isSpeedCruise or isThermalCruise or isSmartFan :
			
			fonv = w83795_read(bus, W83795_REG_FONV(f))
			print("  Fan Output Nonstop Value (FONV): %d%%" % to_perc(fonv))
			fost = w83795_read(bus, W83795_REG_FOST(f))
			if (fost != 0):
				print("  Fan Output Stop Time (FOST):", fost * 0.1, "sec")
			else:
				print("  Fan Output Stop Time (FOST): never stop")
	
	
			ctfs = w83795_read(bus, W83795_REG_CTFS(t))
			#todo : probably in peci unit
			print("  Critical Temperature to Full Speed all fan (CTFS): %d" % (ctfs))
			
			
		if isThermalCruise or isSmartFan:
			#Hystersis of Temperature
			ht = w83795_read(bus, W83795_REG_HT(t))
			#The critical hystersis might be used to lower a cpu even in manual or speed mode. Documentation is unclear. 
			ht_critical = ht  & 0b11110000
			ht_operation = ht & 0b00001111
			print("  Hystersis of critical temperature: %dC" % ht_critical)
			print("  hystersis of operation temperature: %dC" % ht_operation)
			
			
			
		if isThermalCruise :
			ttti = w83795_read(bus, W83795_REG_TTTI(f))
			#ignore the 8th bit as it's reserved
			ttti = ttti & 0b111111
			print("  Target Temperature of Temperature Inputs (TTTI):", ttti, "in PECI unit")
				
			
		print("")
		
	#generic parameters
	
	#Default Fan Speed at Power-on (DFSP)
	defpwm = w83795_read(bus, W83795_REG_DFSP)
	print("Default Fan Speed at Power-on (DFSP): %d%%" % to_perc(defpwm))
	
	#SmartFan Output Step Up Time (SFOSUT)
	stepuptime = w83795_read(bus, W83795_REG_SFOSDT)

	print("Fan output step up time: %g sec" % (float(stepuptime) * 0.1))
	##SmartFan Output Step Down Time (SFOSDT)
	stepdowntime = w83795_read(bus, W83795_REG_SFOSDT)
	print("Fan output step down time: %g sec" % (float(stepdowntime) * 0.1))


def to_degree(val, low=0, hi=127):
	"""Convert hex value to degree."""
	return 127 * val / 255


def to_perc(value):
	"""Convert hex value to percentage."""
	return value * 100 / 255


def from_perc(value):
	"""Convert perc to hex"""
	return (int(value * 255 / 100) & 0xff)
	
def from_degree(value):
	#keven
	return (int(value * 255 / 127) & 0xff)
	
def WriteSettings(bus):
	
	# Read arguments
	args = sys.argv
	pwm_value = None
	if len(args)>1:
		pwm_value = int(args[1])
	
	# Check if Smarts Fan Control is enabled
	fcms1 = w83795_read(bus, W83795_REG_FCMS1)
	fcms2 = w83795_read(bus, W83795_REG_FCMS2) & 0xf
	#debug("FCMDS1: %s, FCMS2: %s" % (fcms1, fcms2))
	if fcms1 !=0 and fcms2 == 0:
		print("Smart Fan Control is not enabled")
		return

	# Extract TEMP with Smart Fan Enabled
	temps = [i for i in range(0,6) if fcms2 & (0x1<<i)]

	# Set the registry value
	if pwm_value:
		print("Set minimum PWM to %s%%" % pwm_value)
		# Change Smart Fan Control value
		for t in temps:
			w83795_write(bus, W83795_REG_SFIV_DCPWM(t)[0], from_perc(pwm_value))
		# Change Minimum PWM
		for f in range(0,6):
			w83795_write(bus, W83795_REG_FONV(f), from_perc(pwm_value))



def main():
	

	#Check if we have the right device.
	try:
		# Open SMBus
		try:
			bus = SMBus(0)
		except:
			print("Failed to open i2c bus (/dev/i2d-0). Make sure i2c-dev module is loaded.")
			return
			
			
		booContinue = CheckChipset(bus)
		if not booContinue:
			#if it's not the correct chipset, stop program
			return
			
	
		#ShowInfo(bus)
		
		parser = argparse.ArgumentParser(description="Utility to show and configure settings of the Nuvoton w83793 chipset")
		parser.add_argument("-s", "--show", help="Show current configuration", action="store_true")
		parser.add_argument("-f", "--fan", type=int, choices=[1, 2, 3, 4, 5, 6, 7, 8], default = 0, help="Select fan to modify")
		parser.add_argument("--sfiv", default=[], nargs = '*', help = "Specify a new set of smartfan values. Specify the temperature then the fan speed for all 6 steps.")
		parser.add_argument("--fcms", choices=['manual','thermal cruise','smart fan'])
		args = parser.parse_args()
		
		if (args.fan > 0 and args.fcms == "thermal cruise"):
			#get fan configuration
			fcms1 = w83795_read(bus, W83795_REG_FCMS1)
			fcms2 = w83795_read(bus, W83795_REG_FCMS2) & 0b00111111
			
			#binary fan value, used for binary and
			#shift number binary 00000001 f bytes to the left, 
			#00000001 shifted 1 time to the left equals 00000010. 
			fbin = 1 << args.fan-1
			inverse = 0xff - fbin
			
			fcms1 = fcms1 & inverse
			print (fcms1)
			
			
			
		
		if (args.fan > 0 and len(args.sfiv) == 12):
			print (args.sfiv)
			#set to zero based
			fan = args.fan-1 
			
			temp = []
			dcpwm = []
					
			
			#from 0 to 5, step by 2
			for index in range(0,11,2):
				#from degree and to degree is weird. from don't work.
				temp.append(from_degree(int(args.sfiv[index])))
				#from perc does work correclty
				dcpwm.append(from_perc(int(args.sfiv[index+1])))
			
			print (temp)
			print (dcpwm)

			
			#print("  Smart Fan Control Table (SFIV)")
			#temp = w83795_read(bus, W83795_REG_SFIV_TEMP(f))
			#print(''.join([("%dC" % to_degree(v)).rjust(6) for v in temp]))

			#dcpwm = w83795_read(bus, W83795_REG_SFIV_DCPWM(f))
			#print(''.join([("%d%%" % to_perc(v)).rjust(6) for v in dcpwm]))
			#print('')
			
			
		
		if (args.show):
			ShowInfo(bus)

			
		
#old stuff from original developper
		#for t in range(0,6):
		#  ctfs = w83795_read(bus, W83795_REG_CTFS(t))
		#  print("T%sCTFS: %s" % (t, to_degree(ctfs)))
		#for f in range(0,6):
		#  w83795_write(bus, W83795_REG_FONV(f), 50)

		#w83795_write(bus, W83795_REG_SFIV_DCPWM(0)[0], 50)
		#

		#w83795_write(bus, W83795_REG_SFIV_TEMP(0)[0], 85)
		#w83795_write(bus, W83795_REG_SFIV_TEMP(1)[0], 85)

	finally:
		bus.close()


if __name__ == "__main__":
		main()

smx8fancontrolif

#!/usr/bin/env python3
#
# To use to SET THE VALUES
# 
#######################
# smx8fancontrolif -m smart -p 01,05,10,20,40,80 -t 25,30,40,50,60,70 -H 2
#######################
# smx8fancontrolif -m cruise -t 50 -H 5 # cruise
#
# Licensed to the Apache Software Foundation (ASF) under one
# or more contributor license agreements.  See the NOTICE file
# distributed with this work for additional information
# regarding copyright ownership.  The ASF licenses this file
# to you under the Apache License, Version 2.0 (the
# "License"); you may not use this file except in compliance
# with the License.  You may obtain a copy of the License at
# 
#   http://www.apache.org/licenses/LICENSE-2.0
# 
# Unless required by applicable law or agreed to in writing,
# software distributed under the License is distributed on an
# "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
# KIND, either express or implied.  See the License for the
# specific language governing permissions and limitations
# under the License.

import sys
import argparse
from smbus2 import SMBus
from contextlib import contextmanager

# 
# All register ceom from
# https://github.com/torvalds/linux/blob/5924bbecd0267d87c24110cbe2041b5075173a25/drivers/hwmon/w83795.c
# 
#

ADDRESS=0x2f

NUVOTON_VENDOR_ID = 0xa3
CHIP_ID = 0x79

W83795_REG_BANKSEL = 0x00

# Fan Control Mode Selection Registers (FCMS)
W83795_REG_FCMS1 = 0x201
W83795_REG_FCMS2 = 0x208
W83795_REG_TFMR = lambda index: 0x202 + index
W83795_REG_TSS = lambda index: 0x209 + index

W83795_REG_SFIV_TEMP = lambda index: range(0x280 + index * 0x10, 0x280 + index * 0x10 + 7)
W83795_REG_SFIV_DCPWM = lambda index: range(0x288 + index * 0x10, 0x288 + index * 0x10 + 7)

W83795_REG_CTFS = lambda index: 0x268 + index

#Fan Output PWM Frequency Prescalar (FOPFP)
W83795_REG_FOPFP = lambda index: 0x218 + index
#Fan Output Nonstop Value (FONV)
W83795_REG_FONV = lambda index: 0x228 + index
#Hystersis of Temperature (HT)
W83795_REG_HT = lambda index: 0x270 + index
#Target Temperature of Temperature Inputs
W83795_TTTI = lambda index: 0x260 + index
#Read temperature
W83795_REG_VRLSB = 0x3C
W83795_REG_TEMP_READ = [0x21, 0x22, 0x23, 0x24, 0x1f, 0x20]

FANS = range(0,8)
TEMPS = range(0,6)

@contextmanager
def bank(bus, value):
  prev_value = w83795_set_bank(bus, value)
  yield
  w83795_set_bank(bus, prev_value)


def w83795_set_bank(bus, bank):
  assert bank in [0,1,2,3]
  # Read current bank value
  cur_bank = bus.read_byte_data(ADDRESS, W83795_REG_BANKSEL)
  # If the bank is already set, nothing to do
  if cur_bank == bank:
    return cur_bank
  # Change the bank
  bus.write_byte_data(ADDRESS, W83795_REG_BANKSEL, bank)
  # Return previous bank value
  return cur_bank


def w83795_write(bus, reg, value):
  """
  Write into the given registry.
  """
  with bank(bus, reg >> 8):
    return bus.write_byte_data(ADDRESS, reg & 0xff, value & 0xff)


def w83795_read(bus, reg):
  """
  Read the given registry.
  """
  
  if hasattr(reg, '__iter__'):
      with bank(bus, reg[0] >> 8):
        return map(lambda r: bus.read_byte_data(ADDRESS, r & 0xff), reg)
  with bank(bus, reg >> 8):
    return bus.read_byte_data(ADDRESS, reg & 0xff)


def to_degree(val, low=0, hi=127):
  """Convert hex value to degree."""
  print("to_degree val", val)
  return val


def to_perc(value):
  """Convert hex value to percentage."""
  return value * 100 / 255


def from_degree(value):
  """Convert degree to hex"""
  value = max(min(int(value) + 1,127),0)
  return value

def from_perc(value):
  """Convert perc to hex"""
  value = max(min(int(value) + 1,100),0)
  return int(value * 255 / 100) & 0xff


def main():
  # Read arguments
  parser = argparse.ArgumentParser(description='Change SuperMicro X8 Fan Control.')
  parser.add_argument('-m', '--mode', type=str, choices=['smart', 'cruise'], help='Set the fan mode: smart or cruise. smart: to use Smart Fan mode. cruise: to use Thermal Cruise mode.')
  parser.add_argument('-p', '--pwm', type=str, help='Set Fan Duty (in percentage).')
  parser.add_argument('-t', '--temp', type=str, help='Set Temperature (in Celsius) associated to pwm.')
  parser.add_argument('-H', '--hystersis', type=int, help='Set Hystersis value in degree (0-15)')
  args = parser.parse_args()

  # Open SMBus
  try:
    bus = SMBus(0)
  except:
    print("Failed to open i2c bus (/dev/i2d-0). Make sure i2c-dev module is loaded.")
    return
  #Check if we have the right device.
  try:
    vendor = w83795_read(bus, 0xfd)
    chipid = w83795_read(bus, 0xfe)
    #debug("vendor %s, chipid %s" % (vendor, chipid))
    if vendor != NUVOTON_VENDOR_ID or chipid != CHIP_ID:
      print("unexpected vendor %s, chipid %s" % (vendor, chipid))
      return

    # Check if Smarts Fan Control is enabled
    if args.mode == 'smart':
        # Check arguments
        if not args.pwm or not args.temp:
          print('pwm and temp are required')
          return
        pwm = args.pwm.split(',')
        temp = args.temp.split(',')
        if len(pwm) != len(temp):
          print("pwm and temp must have the same number of values")
          return

        # Change Smart Fan Control value
        for i in range(0,7):
          p = pwm[i] if i < len(pwm) else pwm[-1]
          tt = temp[i] if i < len(temp) else temp[-1]
          print("Set Smart Fan Control %s%% - %sC" % (p, tt))
          for t in TEMPS:
            w83795_write(bus, W83795_REG_SFIV_DCPWM(t)[i], from_perc(p))
            w83795_write(bus, W83795_REG_SFIV_TEMP(t)[i], from_degree(tt)*2)

        # Change Minimum PWM
        for f in FANS:
          w83795_write(bus, W83795_REG_FONV(f), from_perc(pwm[0]))
        # Change critical Temp
        for t in TEMPS:
          w83795_write(bus, W83795_REG_CTFS(t), from_degree(temp[-1]))

        # Set Smart Fan Control Mode T6FC - T1FC
        w83795_write(bus, W83795_REG_FCMS1, 0x0)
        w83795_write(bus, W83795_REG_FCMS2, 0x3f)

    elif args.mode == 'cruise':
        
        # Check arguments
        if not args.temp:
          print('temp is required')
          return
        temp = int(args.temp)

        print("Set Thermal Cruise %sC" % (temp,))
        for t in TEMPS:
          w83795_write(bus, W83795_TTTI(t), from_degree(temp))

        # Change critical Temp
        for t in TEMPS:
          w83795_write(bus, W83795_REG_CTFS(t), from_degree(80))

        # Set Thermal Cruise Mode.
        w83795_write(bus, W83795_REG_FCMS1, 0x0)
        w83795_write(bus, W83795_REG_FCMS2, 0x0)

    # Set hystersis
    if args.hystersis:
      ht = max(min(args.hystersis,15),0)
      print("Set hystersis %sC" % ht)
      # Change Smart Fan Control value
      for t in range(0,6):
        w83795_write(bus, W83795_REG_HT(t), ht)

    if args.mode or args.pwm or args.temp or args.hystersis:
      return

    # Check if Smarts Fan Control is enabled
    fcms1 = w83795_read(bus, W83795_REG_FCMS1)
    fcms2 = w83795_read(bus, W83795_REG_FCMS2) & 0xff

    # Default to show all data.
    for t in TEMPS:
      print("Temp%s to Fan mapping Relationships (T%sFMR)" % (t+1, t+1))
      tfmr = w83795_read(bus, W83795_REG_TFMR(t))
      fans= [i+1 for i in FANS if tfmr & (0x1<<i)]
      print(' '.join(['Fan%s' % i for i in fans]))

      print("Smart Fan Control Table (SFIV)")
      temp = w83795_read(bus, W83795_REG_SFIV_TEMP(t))
      print(''.join([int("%sC" % to_degree(v)).rjust(6) for v in temp]))

      dcpwm = w83795_read(bus, W83795_REG_SFIV_DCPWM(t))
      print(''.join([int("%s%%" % to_perc(v)).rjust(6) for v in dcpwm]))

      ttti = w83795_read(bus, W83795_TTTI(t))
      print("Thermal Cruise (TTTI): %sC" % (ttti,))

      ctfs = w83795_read(bus, W83795_REG_CTFS(t))
      print("Critical Temperature (T%sCTFS): %sC" % (t, to_degree(ctfs)/2))

      ht = w83795_read(bus, W83795_REG_HT(t)) & 0b1111
      print("Hysteresis (HT%s): %sC" % (t, ht))

      tmp = w83795_read(bus, W83795_REG_TEMP_READ[t])
      print("Current Temperature (TEMP%s): %sC" % (t, to_degree(tmp),))

      print('---')

    for f in FANS:
      fonv = w83795_read(bus, W83795_REG_FONV(f))
      print("Fan%s Output Nonstop Value (F%sONV): %s%%" % (f+1, f+1, to_perc(fonv)))

    #for f in range(0,6):
    #  w83795_write(bus, W83795_REG_FONV(f), 50)
    #w83795_write(bus, W83795_REG_SFIV_DCPWM(0)[0], 50)
    #w83795_write(bus, W83795_REG_SFIV_TEMP(0)[0], 85)
    #w83795_write(bus, W83795_REG_SFIV_TEMP(1)[0], 85)

  finally:
    bus.close()


if __name__ == "__main__":
    main()

Thanks for your fork script. It works fine on my supermicro X8DT3-F. I just wanted to share my success and add my own to the treasury of success.