GPIO

The BM1684 chip contains 3 groups of GPIO controllers, each of which
controls 32 GPIOs, which correspond to the Linux device nodes as
follows:

For example, to operate "GPIO6", you need:

Number conversion: The physical number is 6, the corresponding logical
number is (480 + (6 - 0)) = 486, 0 represents the start of the GPIO
physical number

Export the GPIO, run as root user:  echo 486 >/sys/class/gpio/export

Operate GPIO, set to read input or output specified value:  cd
/sys/class/gpio/gpio486 # set input mode echo in >direction cat value
# set output mode echo out >direction # output low level echo 0 >value
# output high level echo 1 >value

There are a few things to note:

If the GPIO has been applied by other drivers, it cannot be exported
successfully, and subsequent read and write operations cannot be
performed.

Involving the multiplexing of IO functions, if the function of the pin
is already GPIO, the above method can be used; otherwise, the pinctrl
state must be specified in the device tree.

Generally speaking, if you want to easily operate a GPIO in the user
layer, you can add it as a GPIO-LED in the device tree. Please refer
to "linux-linaro-
stable/arch/arm64/boot/dts/bitmain/bm1684_firefly.dtsi" for details.