Hello,
Configuring a pad for a specific functionality requires the following actions:
1.
Check in the Device Tree if the pad is used by other peripheral modules, because a pad can be configured only once in device. Such functionality has to be "disabled" in order to avoid pins conflict.
2.
Check what functionalities can be export the targeted pad in include/dt-bindings/pinctrl/pins-imx8mm.h:
Macros are defined using the convention documented here.
Besides, this type of macro, a sixth value, the pad configuration has to be added for full pinmux setup. The pad configuration (IOMUXC_SW_PAD_CTL_PAD_*) is done in order to select Internal Pull Up Resistors, Hysteresis Enable, Internal Pull Down Resistors, Open Drain Enable, Slew Rate and Drive Strength.
I've sent You more information about GPIO directly.
Regards,
Yuri.