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I'm running dualboot Windows 10 and Ubuntu 18.04 (using the respin from this link). Everything works properly, however the fans are continuously going on and off. The CPU temp is between 39 - 42 degrees celsius. I think the fans are activated somewhere within this range, then cool the CPU and thus get the signal again to stop the fans, etc. On Windows, the fans are completely off at idle or light work.

What I already did

• lm_sensors: cannot find the fans even after "sudo sensors-detect"




• i8kutils: Cannot find /prod/i8k




• BIOS updated to version 1.5.0




• Kernel is version 4.19.2-041902-generic




• Installed and activated thermald, tlp, powertop and intel-microcode.



• 
  

  Set the graphics card to Intel for power-saving

  
  
  
  
  
  • "sudo prime-select intel"
  
  
  
  



• Undervolt by -140 mV on core and CPU, and -40 mV on iGPU (using this link)




• Installed smbios-utils and set it to different modes (balanced, cool-bottom, quiet, performance)




• Disable fan BIOS control (see link)

All without any luck.

What I still want to do

• Repasting

Stats

sudo tlp stat



+++ System Info



System         = Dell Inc. XPS 15 9570

BIOS           = 1.5.0

Release        = Ubuntu 18.04.1 LTS

Kernel         = 4.19.2-041902-generic #201811132032 SMP Tue Nov 13 20:34:19 UTC 2018 x86_64

/proc/cmdline  = BOOT_IMAGE=/boot/vmlinuz-4.19.2-041902-generic root=UUID=5394fef0-92d3-4753-a6a1-fd7b5c4f9cea ro quiet splash quiet acpi_rev_override=1 acpi_osi=Linux scsi_mod.use_blk_mq=1 nouveau.modeset=0 nouveau.runpm=0 mem_sleep_default=deep vt.handoff=1

Init system    = systemd v237

Boot mode      = UEFI



+++ Temperatures

CPU temp               =    43 [°C]

Fan speed              = (not available)

I guess that Ubuntu is unable to see the fans and is thus unable to take control over them. Any suggestions to gain control over them?

I found a solution to my own problem.

To see the fans with "lm_sensors"

Add dell-smm-hwmon to modules

sudo echo "options dell-smm-hwmon restricted=0 force=1" > /etc/modprobe.d/dell-smm-hwmon.conf

sudo echo "dell-smm-hwmon" > /etc/modules

sudo update-initramfs -u

Reboot and the fans should be visible with

sensors

dell_smm-virtual-0

Adapter: Virtual device

fan1:           0 RPM

fan2:           0 RPM

To take over control of your fans

Then follow this guide to install i8kutils

sudo apt install i8kutils

sudo echo "i8k" > /etc/modules

sudo echo "options i8k force=1" > /etc/modprobe.d/i8k.conf

Reboot

sudo modprobe i8k force=1

Configure i8kutils

sudo gedit /etc/i8kmon.conf

Finally, disable Dell BIOS Fan Control with this program by TomFreudenberg to let i8kutils take over.

git clone https://github.com/TomFreudenberg/dell-bios-fan-control.git

cd dell-bios-fan-control

make

sudo dell-bios-fan-control 0

Simply run i8kmon to control your fans or try ik8fan to manually control your fans.

i8kfan 2 2

A less intrusive method to get less temperature (and therefore no fans are required) is using powertop.

 cat /sys/bus/pci/devices/0000:01:00.0/power/control # (on?. That is bad)

 sudo powertop --auto-tune

 cat /sys/bus/pci/devices/0000:01:00.0/power/control # (auto?. That is good)

In order to get the changes permanently, see How do I make Powertop changes permanent? . However, in the help of TLP it is said that 'attempting to apply powertop's --auto-tune settings on each boot will conflict with TLP'. By now, it is working fine for me (XPS 15 9570, bios 1.5).

Are the changes made by Dell BIOS Fan Control by TomFreudenberg written to the BIOS firmware ?
I have a ubuntu/windows dual boot and would like to make sure that this linux configuration tweaks will not affect the fan control under windows.
Thanks!

EDIT: I meticulously applied all steps above and fans don't spin automatically when dell-bios-fan-control 0 is used, with i8kmon in daemon mode. My CPU temps went up to ~90°C while browsing the web and reading PDFs. Anything missing from this guide to make sure this works ?