Troubles booting kernel with new imx8 board

[marc at cpdesign.com.au]

Hi all, 

I'm trying to get barebox going for a new imx8mp based board. I can 
successfully power on and get to a barebox prompt etc and fiddle with gpios, 
files on sd, memtest etc, but when booting to kernel it will hang. Note though 
that the board boots ok with u-boot (using exact same kernel image).

I'm trying to figure out what is different between booting via uboot and 
barebox, I'm new to imx8 so have been going down a few rabbit holes...

Disabling various drivers (eg imx-cpufreq-dt) in the kernel will get past the 
hang, but result in a crash later on in the boot sequence. Disabling that may 
get further but will result in a crash somewhere else.
My instinct is that its something to do with sdma, but a lot of this is still 
a black box to me.

Any hints or suggestions are very welcome! (I can give more info but didn't 
want to dump everything straight away)

- board is based on an imx8mp module from solidrun
- boots kernel ok using u-boot (u-boot version provided by solidrun, based on 
NXP versions)
- I used the same ddr timings from u-boot
- also using same versions of firmware-imx (8.16) and ATF (2.8)

Cheers
Marc