GPIO's are listed under /sys/class/gpio

Linux GPIO Number = <GPIO_bank – 1> × 32 + <GPIO Port number>

example

Linux GPIO Number = <GPIO_bank x 32> + <GPIO Port number>

example

root@MBaXXX:~ echo <gpionr> >/sys/class/gpio/export                  // export GPIO pin
root@MBaXXX:~ echo out > /sys/class/gpio/gpio<gpionr>/direction      // set GPIO direction
root@MBaXXX:~ echo 1 > /sys/class/gpio/gpio<gpionr>/value            // toggle GPIO to high 
root@MBaXXX:~ echo 0 > /sys/class/gpio/gpio<gpionr>/value            // toggle GPIO to low 

example

root@MBaXXX:~ echo 34 >/sys/class/gpio/export
root@MBaXXX:~ echo out >/sys/class/gpio/gpio34/direction
root@MBaXXX:~ echo 1 > /sys/class/gpio/gpio34/value
root@MBaXXX:~ echo 0 > /sys/class/gpio/gpio34/value

root@MBaXXX:~ echo „<gpionr>" >/sys/class/gpio/export                  // export GPIO pin 
root@MBaXXX:~ echo in > /sys/class/gpio/gpio<gpionr>/direction       // set GPIO direction
root@MBaXXX:~ cat /sys/class/gpio/gpio<gpionr>/value                   // read GPIO value

example

root@MBaXXX:~ echo 34 > /sys/class/gpio/export
root@MBaXXX:~ echo in > /sys/class/gpio/gpio34/direction
root@MBaXXX:~ cat /sys/class/gpio/gpio34/value

It is possible to toggle the GPIO's in U-Boot with the gpio command. To use gpio command the desired gpio pin number has to be given as parameter to the command. The following bitmask applies to GPIO pin number in U-Boot:
[PPPP P_BBB] P = pin, B = bank

For example we toggle GPIO0_24 on MBa28

GPIO0_24 = GPIO Bank 0, Pin 24, GPIO0_24 = 11000