Resolved! STM32MP1 ECO Unused GPIO busy after gpioset
Kernel tree does not assign any driver to pin PZ2. After gpioset -c gpiochip11 2=1, the pins goes actually high (from low) but the gpioset program stalls. SSH at that moment into the device shows: line 0: "PZ0" input line 1: "PZ1" input line 2: "PZ2"...