[U-Boot] What can cause gpio_request return negative value

[Nemanja Savic]

Hi all,

I am struggling with porting our old board init code for a sabre auto based
custom board with i.MX6 DualLite processor. The code used to work in our
older u-boot version, but what I saw in mx6qsabreauto.c is that the new
style is by using new driver model which means the gpio should be first
requested. However gpio_request returns negative value in my case. Where
could the problem be? As far as I could see our device tree doesn't reserve
this pin for other purpose. It is even not mentioned there. The only thing
related to those pins are iomux pin definitions in the device tree but
removing that doesn't help at all. Also device tree for the Sabre Auto
board doesn't mention gpio pins that they use in their u-boot. I am dealing
with 2017.03 version of u-boot.