Enabling GPIO6_IO15 on efus A9 (using fsimx6-Y2022.09)

    Dear Sirs,


    I am using efus A9 (quad core) Rev 1.21 and EFUS-SINTF board rev 1.50 and I am trying to enable GPIO6_IO15 (/sys/class/gpio/gpio175).

    My environment is based on Yocto image fsimx6-Y2022.09.


    Basically I want to use pin multiplexing MX6QDL_PAD_NANDF_CS2__GPIO6_IO15.


    DEVICE TREE CHANGES:


    I modified default efusa9q.dts and defined board revision as 121 (from 120):

    Code
    1. #define CONFIG_EFUSA9_BOARD_REVISION 121


    As the default signal function is CAM_MCLK, I disabled all camera defines in efusa9q.dts:



    Then I checked efusa9qdl.dtsi and I noticed that in hoggrp-1 there is still a definition for MX6QDL_PAD_NANDF_CS2__CCM_CLKO2 despite the fact that camera is disabled, so I replaced it with MX6QDL_PAD_NANDF_CS2__GPIO6_IO15 (though I think it is not needed).


    Code
    1. imx6qdl-efusa9 {
    2. /* Pin configs that don't belong anywhere else */
    3. pinctrl_hog_1: hoggrp-1 {
    4. fsl,pins = <
    5. /* Audio clock */
    6. MX6QDL_PAD_GPIO_0__CCM_CLKO1 0x130b0
    7. #if (CONFIG_EFUSA9_BOARD_REVISION >= 121)
    8. /* Camera clock 24MHz */
    9. /* MX6QDL_PAD_NANDF_CS2__CCM_CLKO2 0x110b0 */
    10. MX6QDL_PAD_NANDF_CS2__GPIO6_IO15 0x1b0b0


    Then I've built device tree, applied it to panel, booted device and exported GPIO:

    Code
    1. echo 175 > /sys/class/gpio/export
    2. echo out > /sys/class/gpio/gpio175/direction
    3. echo 1 > /sys/class/gpio/gpio175/value


    According to efus A9 GPIO Reference Card, GPIO6_IO15 shall be available on EFUS-SINTF pins J18_13 and J20_12.


    However when measuring J20_12 with multi-meter (and J18_13 though it is difficult to measure that one), I still get 1.54V no matter what gpio175/value I set. I do not have oscilloscope, but it seems to me that the clock signal CLKO2 is still there.


    I am not having these issues with GPIO5_IO19 (/sys/class/gpio/gpio147) originally defined as CAM_HREF. I can control that one via /sys/class/gpio/gpio147 since I disabled the camera.


    What could be interfering with this pin? Is there something additional that I need to disable to enable GPIO6_IO15 properly?


    Thanks,

    Jaroslav