GPIO8 on Apalis i.MX6

Technical Support
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1

I want to use GPIO8 (Apalis name) / gpio6 (Linux name) for a touchscreen on a custom carrier board. I adjusted the device tree and have a kernel module for touchscreen implementation.

It works fine but only if I unexport gpio6 first. Is gpio6 used in some configuration or driver during linux boot?
On a clean Linux install I get:

root@apalis-imx6:~# cat /sys/kernel/debug/gpio
gpiochip0: GPIOs 0-31, parent: platform/209c000.gpio, 209c000.gpio:
 gpio-0   (                    |usb_host_vbus       ) out hi
 gpio-6   (                    |sysfs               ) in  hi
 gpio-25  (                    |phy-reset           ) out hi

gpiochip1: GPIOs 32-63, parent: platform/20a0000.gpio, 20a0000.gpio:
 gpio-38  (                    |sysfs               ) in  hi
 gpio-39  (                    |sysfs               ) in  hi

gpiochip2: GPIOs 64-95, parent: platform/20a4000.gpio, 20a4000.gpio:
 gpio-77  (                    |enable              ) out hi
 gpio-86  (                    |usb_otg_vbus        ) out lo
 gpio-92  (                    |usb_host_vbus_hub   ) out hi

gpiochip3: GPIOs 96-127, parent: platform/20a8000.gpio, 20a8000.gpio:
 gpio-116 (                    |cd                  ) in  lo

gpiochip4: GPIOs 128-159, parent: platform/20ac000.gpio, 20ac000.gpio:

gpiochip5: GPIOs 160-191, parent: platform/20b0000.gpio, 20b0000.gpio:

gpiochip6: GPIOs 192-223, parent: platform/20b4000.gpio, 20b4000.gpio:

For the kernel module to work I had to add a “gpio_free()” before my “gpio_request()”. I would like to know why the gpio was exported in the first place and if it’s ok to just free the gpio?

2

Hi

We export all GPIOs which are not assigned internally to our demo images pinout with the package built from this recipe. This is done with a systemd service which executes this script during boot.

If you do not need any exporting remove the package from the image recipe. Alternatively adapt the script to your needs.

Max