nx1.info | Adjusting NVIDIA Jetson Fan settings

The fan configuration file on the NVIDIA Jetson Orin NX is stored in the file: /etc/nvfancontrol.conf

1. Default Configuration File [^]

By default, this file contains the following:

matoha@orin-nx-1:~$ cat /etc/nvfancontrol.conf
# Copyright (c) 2022, NVIDIA CORPORATION.  All rights reserved.

POLLING_INTERVAL 2

<FAN 1>
        TMARGIN ENABLED
        FAN_GOVERNOR cont {
                STEP_SIZE 10
        }
        FAN_CONTROL close_loop {
                RPM_TOLERANCE 100
        }
        FAN_PROFILE quiet {
                #TEMP   HYST    PWM     RPM
                0       0       255     6000
                10      0       255     6000
                11      0       187     4000
                31      0       187     4000
                70      0       0       0
                105     0       0       0
        }
        FAN_PROFILE cool {
                #TEMP   HYST    PWM     RPM
                0       0       255     6000
                35      0       255     6000
                70      0       0       0
                105     0       0       0
        }
        THERMAL_GROUP 0 {
                GROUP_MAX_TEMP 105
                #Thermal-Zone Coeffs Max-Temp
                CPU-therm 20,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0 0
                GPU-therm 20,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0 0
                SOC0-therm 20,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0 0
                SOC1-therm 20,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0 0
                SOC2-therm 20,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0 0
        }
        FAN_DEFAULT_CONTROL close_loop
        FAN_DEFAULT_PROFILE quiet 
        FAN_DEFAULT_GOVERNOR cont
        KICKSTART_PWM 64

There are two fan profiles defined, "quiet" (which is set as the default in the line):

FAN_DEFAULT_PROFILE quiet

and a "cool" profile, which may be set as the default by modifying the above line.

2. How Fan Profiles Work [^]

The way that these profiles work is not exactly intuitive so read carefully: The line TMARGIN ENABLED means that the profiles use thermal margins in their definitions. The thermal margin is defined as the difference between the maximum temperature and the current temperature: $$T_{\text{margin}} = T_{\text{max}} - T_{\text{current}}$$ where the maximum temperature is defined in the line:

GROUP_MAX_TEMP 105

What this means is that the first line in both the fan profiles:

#TEMP   HYST    PWM     RPM
0       0       255     6000

Will set the fan speed to 6000 RPM when the thermal margin is 0, (which corresponds to a current temperature of 105c). Notice that the second line in the cool profile:

35      0       255     6000

Sets a fan speed of 6000 when there is a thermal margin of 35 or less, which corresponds to any temperature at or above 70c (105-35=70). We could in theory just force the fans to always run at full speed by creating and activating the following profile:

FAN_PROFILE full_speed {
        #TEMP   HYST    PWM     RPM
        0       0       255     6000
        105     0       255     6000
}

But this is probably not the best idea as it could wear out the fan faster.

3. How to Change the Fan Profile [^]

Changing the default fan profile requires editing the line containing FAN_DEFAULT_PROFILE in /etc/nvfancontrol.conf using sudo via one's editor of choice: vi, vim, nano, etc... To change the fan settings and apply the changes, the following sequence of commands should be executed:

# 1. Stop the service
> sudo systemctl stop nvfancontrol

# 2. (Edit /etc/nvfancontrol.conf here using sudo)
> sudo vim /etc/nvfancontrol.conf

# 3. Delete the cached status file
> sudo rm -f /var/lib/nvfancontrol/status

# 4. Start the service
> sudo systemctl start nvfancontrol

# 5. Verify the active profile
> sudo nvfancontrol -q

4. PWM Column vs Closed-Loop RPM [^]

In the control file, there is a PWM column (Pulse Width Modulation). This is an alternative means of defining the fan speed and specifies the speed as a percentage (0-100%) but is defined using an 8 bit integer (0-255). However since FAN_CONTROL close_loop is enabled, nvfancontrol will preferentially use the RPM column. (If open_loop mode was enabled then the PWM column would be used).

5. Thermal Sensors & Group Prioritization [^]

Multiple temperature sensors exist in the Jetson's hardware: CPU-therm, GPU-therm, SOC0-therm, SOC1-therm, SOC2-therm. Since all these sensors have been defined in the THERMAL_GROUP 0 using the same parameters, nvfancontrol will simply govern the fan control based on whichever sensor is running the hottest (has the lowest margin).

THERMAL_GROUP 0 {
        GROUP_MAX_TEMP 105
        #Thermal-Zone Coeffs Max-Temp
        CPU-therm  20,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0 0
        GPU-therm  20,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0 0
        SOC0-therm 20,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0 0
        SOC1-therm 20,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0 0
        SOC2-therm 20,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0 0
}

6. Temporarily Force Max Fan Speed [^]

To force full fan speed:

> sudo jetson_clocks --fan

To restore:

> sudo jetson_clocks --restore

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