In some cases, i.MX board connect to different module. It has very tiny changes, such as just one gpio different driver strength.
We can build an entire new software to handle this requirement.
Here we introduce another way, using u-boot to modify the device tree(dtb) at runtime.
Here is u-boot fdt command for
How to use gpio-hog demo
https://community.nxp.com/t5/i-MX-Processors-Knowledge-Base/How-to-use-gpio-hog-demo/ta-p/1317709
run loadfdt
fdt addr ${fdt_addr_r}
fdt print /soc/bus/pinctrl/uart3grp
fdt rm /soc/bus/pinctrl/uart3grp
fdt print serial2
fdt set serial2 status disabled
fdt print serial2
fdt print gpio4
fdt resize
fdt mknode gpio4 gpio_hog_demo
fdt set gpio4/gpio_hog_demo gpio-hog
fdt set gpio4/gpio_hog_demo gpios <7 0>
fdt set gpio4/gpio_hog_demo output-high
fdt print gpio4
run mmcargs
run loadimage
booti ${loadaddr} - ${fdt_addr_r}
root@imx8mmevk:~# cat /sys/kernel/debug/gpio
gpiochip0: GPIOs 0-31, parent: platform/30200000.gpio, 30200000.gpio:
gpio-5 ( |PCIe DIS ) out hi
gpio-13 ( |ir-receiver ) in hi IRQ ACTIVE LOW
gpio-15 ( |cd ) in hi IRQ ACTIVE LOW
gpiochip1: GPIOs 32-63, parent: platform/30210000.gpio, 30210000.gpio:
gpio-38 ( |? ) out hi
gpio-42 ( |reset ) out lo ACTIVE LOW
gpio-51 ( |regulator-usdhc2 ) out lo
gpiochip2: GPIOs 64-95, parent: platform/30220000.gpio, 30220000.gpio:
gpio-80 ( |status ) out hi
gpiochip3: GPIOs 96-127, parent: platform/30230000.gpio, 30230000.gpio:
gpio-117 ( |PCIe reset ) out hi
gpiochip4: GPIOs 128-159, parent: platform/30240000.gpio, 30240000.gpio:
gpio-135 ( |gpio_hog_demo ) out hi
gpio-141 ( |spi1 CS0 ) out hi ACTIVE LOW
gpio-149 ( |wlf,mute ) out hi ACTIVE LOW
root@imx8mmevk:~# [ 33.758914] VSD_3V3: disabling
dtc_utils-v1.6.1-win-x86_64.zip by msys2
