Power Mode and Fan Control

Problem

No fan and power mode control is available in Linux.

Solution

There is a ec-su_axb35-linux kernel module written by Christoph Metz.

It allows you to:

• read current fan speeds and modes
• switch modes of each of the three available fans
• control fan speed in fixed mode
• control fan speed with custom curves in curve mode
• read current power mode
• change current power mode
• read current APU temperature

Generic Installation

The following assumes that you're doing it under root or with sudo.

1. Install module building dependencies (depends on your distro, on debian should be build-essential and linux-headers-$(uname -r) packages).
2. Clone the repo with git clone https://github.com/cmetz/ec-su_axb35-linux.git.
3. Build and install the module with cd ec-su_axb35-linux && make install.
4. Try loading the module with modprobe ec_su_axb35 and check your dmesg afterwards. You should see the Sixunited AXB35-02 EC driver loaded message.
5. Run scripts/info.sh and check that all information is there.
6. Run scripts/test_fan_mode_fixed.sh, it should test your fans on all 6 fixed levels.
7. If everything is good, you can make the module automatically load on system boot with echo ec_su_axb35 >> /etc/modules.

Usage

Reading and writing all of the parameters happens through sysfs with /sys/class/ec_su_axb35 path. You can find detailed information in the repo's readme file.

Some examples:

• cat /sys/class/ec_su_axb35/fan2/rpm to get current rpm of fan2
• echo fixed > /sys/class/ec_su_axb35/fan3/mode && echo 2 > /sys/class/ec_su_axb35/fan3/level to switch fan3 to fixed mode and set speed to level 2
• echo balanced > /sys/class/ec_su_axb35/apu/power_mode to set power mode to balanced (85W)

You can also call su_axb35_monitor anywhere to monitor all available values in realtime:

To apply specific settings at system startup, place them in your rc.local file or utilize any other methods for executing commands during boot, such as creating a systemd unit. In the future, these parameters will also be configurable through module options.

Custom Curves

The custom curves define temperature thresholds for fan power levels:

• Ramp-up curve (/sys/class/ec_su_axb35/fanX/rampup_curve): temperature points where fan increases to the next level
• Ramp-down curve (/sys/class/ec_su_axb35/fanX/rampdown_curve): temperature points where fan decreases to the previous level

For example, with these settings:

• rampup_curve = 60,70,83,95,97
• rampdown_curve = 40,50,80,94,96

When CPU is heating up:

• Below 60°: Fan at level 0 (minimum)
• At 60°: Increases to level 1
• At 70°: Increases to level 2
• At 83°: Increases to level 3
• At 95°: Increases to level 4
• At 97°: Increases to level 5 (maximum)

When CPU is cooling down:

• Above 96°: Fan stays at level 5
• Below 96°: Decreases to level 4
• Below 94°: Decreases to level 3
• Below 80°: Decreases to level 2
• Below 50°: Decreases to level 1
• Below 40°: Decreases to level 0

This creates a buffer at each level that prevents the fan from rapidly switching between speeds when temperature fluctuates around threshold values.

Curves are being applied only when curve mode is set on a specific fan, each fan has their own curves.

Fine-tuning Power Limits

If you want more gradual control over power modes, there's a RyzenAdj utility.

Main 3 parameters we are interested in are:

• STAPM LIMIT (sustained power draw)
• PPT LIMIT FAST (boost power draw)
• PPT LIMIT SLOW (average power draw)

Default values on all 3 selectable power modes (use ryzenadj --info to read them):

Example on setting the power limit to static 100W with no boost:
ryzenadj --stapm-limit=100000 --fast-limit=100000 --slow-limit=100000

Note that changing the power mode via the EC controller (using ec-su_axb35-linux or otherwise) resets these values to their defaults.

Relevant Pages

• Guides/Hardware-Monitoring
• Guides/Power-Modes-and-Performance