IMX8MP unused pins configuration and iomuxc Linux driver

[jgrossholtz]

Hi,

My questions relates with a board that is using an imx8mp, but I guess the answer would be similar to other i.MX processors.

I have a board with a SOM. Many pins from the SOM connector are not connected to anything on the baseboard. From what I read here and here those pins must be configured as gpio input and pull-up.

I would like to know how to achieve that under Linux and/or U-Boot :

• Is it sufficient to ensure that unused SoC components are marked as unused in the device-tree nodes ? Maybe the default boot state for all unused pins is "pull-up gpio input" or maybe the iomux driver takes care of this default case ?
• Or should those pins be explicitly and individually be configured with the fsl,imx8mp-iomuxc driver and a node to configure all unused pins ?

I was not able to find an example of pinctrl configuration for unused pins within Linux sources. So I guess it is more likely to be the first case ?

I also would like to know what pinmuxing mistakes could lead to damage the SoC and therefore what should I be really careful with ?

Thanks a lot,

[joanxie · Accepted solution]

for unused pins, you can refer to the enclosed file as HW design, for SW, if these pins are not mux for other functions, you can just ignore them

[jgrossholtz]

Thank you @joanxie , it makes sense.