Kontron SMARC-sAL28, Руководство пользователя

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SMARC-sAL28 User Guide. Rev. 1.0
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8/ Implementation Notes
8.1. GPIO
SMARC GPIO0-GPIO11 lines are mapped in Linux in the following way:
Table 27: GPIO
Name Legacy interface:
“/sys/class/gpio” Modern interface: “/dev/gpiochip”
GPIO0 gpio400 GPIO0_CAM0_PWR_N
GPIO1 gpio401 GPIO1_CAM1_PWR_N
GPIO2 gpio402 GPIO2_CAM0_RST_N
GPIO3 gpio403 GPIO3_CAM1_RST_N
GPIO4 gpio404 GPIO4_HDA_RST_N
GPIO5 gpio405 GPIO5_PWM_OUT
GPIO6 gpio406 GPIO6_TACHIN
GPIO7 gpio407 GPIO7
GPIO8 gpio392 GPIO8
GPIO9 gpio393 GPIO9
GPIO10 gpio394 GPIO10
GPIO11 gpio395 GPIO11
These GPIOs could be controlled either over sysfs (legacy approach), as documented in
https://elixir.bootlin.com/linux/v4.14/source/Documentation/gpio/sysfs.txt . For example, following shell script
blinks carrier's LED connected to GPIO5 line:
echo 405 > /sys/class/gpio/export
echo out > /sys/class/gpio/gpio405/direction
while true; do
echo 0 > /sys/class/gpio/gpio405/value
sleep 1
echo 1 > /sys/class/gpio/gpio405/value
sleep 1
done
Or via modern “/dev/gpiochip” interface, information about which and corresponding examples/tools can be found
at following links:
https://elixir.bootlin.com/linux/v4.14/source/include/uapi/linux/gpio.h
https://elixir.bootlin.com/linux/v4.14/source/tools/gpio
https://git.kernel.org/pub/scm/libs/libgpiod/libgpiod.git/tree/README?h=v1.4.x
GPIO5 and GPIO6 are shared with PWM_OUT and TACHIN signals, so one function (fan, gpio)
can be used at the same time.
Also the gpio lines support interrupt handling from userspace. For this purpose the attributes "edge" and "value" in
sysfs should be used. There is a simple program in C language which gratefully illustrate how this interface may be
used by developers: https://developer.ridgerun.com/wiki/index.php?title=Gpio-int-test.c
Plus a gpiomon tool from libgpiod tools, which is provided as part of the BSP, can be used to monitor the GPIO
interrupts. E.g.:
# gpiofind GPIO7
gpiochip4 7