I'm using an Olimex LIME2 board with an A20 processor (actually it's a Olimex A20-SOM, but that shouldn't matter) and trying to use PWM.

 

I have an older image (jessie with Kernel 3.4) where the PWM hardware can be accessed through /sys/class/pwm-sunxi/pwm*/{duty, duty_percent, period, pin, polarity, pulse, run}.

 

Now I'm building a newer image (xenial with Vanilla kernel). It has /sys/class/pwm, but the directory is empty. Any ideas?

 

The fex file is the same for both boards; the relevant section is:

[pwm0_para]
pwm_used = 1
pwm_period = 10000
pwm_duty_percent = 50

[pwm1_para]
pwm_used = 1
pwm_period = 10000
pwm_duty_percent = 50

Same situation here on a Lime2(eMMC) on latest stable using the 4.11.6-sunxi kernel.

 

What I did was add the following the Armbian docs on Allwinner DT overlays to /boot/armbianEnv.txt:

overlay_prefix=sun7i-a20
overlays=pwm

and reboot.

 

But that didn’t fix it either.

 

So I then tried to load the module (unsure which one it would be):

 

modprobe pwm-sun4i
modprobe pwm-fan

 

But that didn’t fix it either.

 

If you have any suggestion, do let me know.