Hello @SimonG,
Upon further investigation, u-boot is not applying the pinctrl from the device tree.
This is likely due to the limited device tree support which is present in u-boot.
A way to guarantee this configuration would be to include it in the board initialization file, please see the attached patch, which does just that for this GPIO pin.
0001-colibri-imx6ull-Configure-GPIO1_IO14-as-GPIO.patch (1.3 KB)
Best Regards,
Bruno