I have troubles to get the GPIO working on my APU.2C4 (Bios 4.6.1) with Debian 9 (Kernel 4.9.0).
I'm able to compile and install the GPIO driver :
gpio_nct5104d: loading out-of-tree module taints kernel.
gpio-nct5104d: Found nct5104d at 0x2e chip id 0xc453
gpio-nct5104d: Device added
It is also possible to write a value:
echo 0 > /sys/class/gpio/export
echo out > /sys/class/gpio/gpio0/direction
echo 1 > /sys/class/gpio/gpio0/value
...and everything looks fine in /sys/kernel/debug/gpio:
gpiochip0: GPIOs 0-7, parent: platform/gpio-nct5104d, gpio-nct5104d, can sleep:
gpio-0 ( |sysfs ) out hi
gpiochip1: GPIOs 10-17, parent: platform/gpio-nct5104d, gpio-nct5104d, can sleep:
Problem: The value (high or low) never appears on the pin.
Solution: Use Bios version 4.0.12 and disable UART C/D in the Bios:
o UART C - Currently Disabled
p UART D - Currently Disabled