I have followed the board integration instructions for RPi 3 found here, except that I am using a Compute Module 3+. I was able to convert the stock Raspbian Stretch Lite 2019-04-08 image to support Mender, using the mender-convert tool as described (though curiously I had to explicitly set the “–storage-total-size-mb 7400” parameter before it would fit in the 8GB eMMC). With this converted image flashed to the CM3+, and the CM3+ connected to my custom PoE carrier board, the board boots successfully however it is not connecting to my network via Ethernet. If I use the stock Raspbian image without converting for Mender, it works and connects fine.
I see in the “Known Issues” section how “Devicetree is not updated”, and other forum posts like this one where it seems the root issue may be related to U-Boot doing some of its own pin muxing instead of honoring the .dtb as supplied in the image.
As we use a custom carrier board, there are various tweaks that we have made and need regarding pin muxing. Is there any simple way to use the mender-convert tool while maintaining our customized pin muxing? Or is our only option to set up a Yocto environment, attempt to modify the U-Boot files to avoid undesired muxing, and build the image that way?
I am new to Yocto and U-Boot, so that seems a bit daunting. Any tips or guidance would be much appreciated.