I am wondering, what 0x14 (or 0x74) should actually mean?
As far as I understand 0x14 equals to 0b10100, which in my opinion, according to Device Tree Customization | Toradex Developer Center , does not represent a valid PAD Control Registers configuration (bit 2 is reserved but set to 1).
Even though for iMX7 (where I have just seen this PAD control register settings a lot in imx7-colibri.dtsi) it seems to me to be a strange configuration for a GPIO pin usage (e.g. 0x14 == 100k pull-down, pull enabled, hysteresis disabled, fast slew rate, X1 drive strength). Would it not rather make sense to enable hysteresis and go for a slow slew rate?
Wait, I think there is something wrong in your device tree documentation for iMX7 (Device Tree Customization | Toradex Developer Center ). According to Chapter 8 of the NXP®/Freescale i.MX 7 application processor reference manual the SLE bit is specified as following:
SLE 1: slow slew rate
SLE 0: fast slew rate
Thus the the SLE setting in imx7-colibri.dtsi seems to be ok. Please correct the documentation accordingly.
The equivalent of i.MX 7 0x14 (100k pull down, slow slew rate) would be 0x2000 on i.MX 6ULL. The equivalent of 0x74 (100k pull up, slow slew rate) would be 0xa000 on i.MX 6ULL.
Since this change might cause side effect I will create a ticket.