I need help freeing a gpio to user space needs

Technical Support
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1

Hi there,

I’m using Linux bsp 2.8.2, i need to get GPIO2_IO15 free from other resources to be used as user GPIO.

I’m starting from an exisiting project, i can reverse DTB to DTS and viceversa but i’m short on yocto original project to check layers and so on.

Through the follow knowledge:

  • Colibri_arm_som_imx7_datasheet.pdf
  • IMX7DRM
  • Various imx7*.dtsi
  • Pinout Designer project

I’m expecting to find GPIO2_15 free to user needs, at the opposite when i dig into sysfs debug features i got:

  gpio-47 (    |  ? ) out Hi

By reverting DTB to DTS i’ve found the pin grouped under gpio6-grp probably due to an Atmel touch screen chip definition found in some imx7*.dtsi.

Now, i moved the gpio into the “main” gpio group (gpio1-grp) but i can’t get to free the gpio.

I’m looking for an hint how to check who is using this GPIO.

Thanks in advance.
Matteo.

2

Further infos from my reversed DTS :

iomuxc@30330000 {
	compatible = "fsl,imx7d-iomuxc";
	reg = <0x30330000 0x10000>;
	pinctrl-names = "default";
	pinctrl-0 = <0x18 0x19 0x1a 0x1b 0x1c>;
	linux,phandle = <0x15>;
	phandle = <0x15>;

	gpio1-grp {..}
	gpio2-grp {..}
	gpio3-grp {..}
	gpio4-grp {..}
	spigpios   {..}
	gpio6-grp { 
            MX7D_PAD_EPDC_DATA15__GPIO2_IO15 (the gpio i'm looking for [gpio2.io[15]) , 
            MX7D_PAD_EPDC_BDR0__GPIO2_IO28 
         }
    .....
    }

There are no other references to this PAD along my DTS.
Should i assume it is used as GPIO but maybe is taken by some kernel modules for example?

3

Another step forward:

iomuxc@30330000 {
     compatible = "fsl,imx7d-iomuxc";
     reg = <0x30330000 0x10000>;
     pinctrl-names = "default";
     pinctrl-0 = <0x18 0x19 0x1a 0x1b 0x1c>; this was missing the hoggroup 6 handle

But nonetheless gpio-47 is not shown in exported gpios, but with ( ? ) question mark on sysfs debug

4

I ended up in rebuilding the whole image, now i moved to bsp 3.0.4, i got my free gpio.

5

Perfect that you found a solution. Thanks for the feedback.