Here are some details about my hardware and build environment
I have the auvidea J120 Rev7 carrier board and have patched the firmware version 3 for Jetpack 4.3
I have the original fan installed on the board and it starts up and runs for a short period of time depending on how long it has been sitting without power connected to the board. The fan will sputter out and stop working and occasionally will give a few spins.
I previously had Jetpack 4.2 installed and firmware version 2.2 and the fan ran all the time at full speed, which from what I read on the forums is the only way the fan is supposed to be able to work on the J120 for all versions of Jetpack >=4.2
I compared these .dtsi files from the kernel_src files provided by auvidea in the firmware versions 2.2 and 3 to see if something changed to cause this issue but no changes were made to these files that other users have cited in other posts.
I am currently looking into trying to pull the GPIO for vdd_fan which is GPIO 244 according to this article from ridgerun. https://developer.ridgerun.com/wiki/index.php?title=JetsonTX2/Linux_PWM_Pulse_Width_Modulator
See “Control Fan PWM (sysfs)” section
echo 244 > export
echo out > direction ; cat direction
Im not yet sure what to echo to the GPIO in order to set the pwm period and duty cycle or if all I need to do is simply set the target_pwm to 255. Ill update this thread once I get more information but I was hoping someone with more experience could give me some guidance.
note that the usual suggestion “echo 255 > /sys/kernel/debug/tegra_fan/target_pwm” does not work and this filepath does not exist on the machine.
I am not really that experienced in interfacing with the GPIO using this approach but I would much rather prefer to have a CLI solution than disable the driver and make the changes to the .dtsi file as referenced in the same ridgerun documentation. Im trying to avoid needing to recompile the kernel and flashing the OS again…
Any suggestions are more than welcome!