Kindly need help debugging start of kernel

[Matthias Schoepfer]

Hi!

We have a Dragonboard 410c. We chainload u-boot from little kernel (lk), 
and from there the linux kernel obviously. All of it (not little kernel) 
is build within yocto / Openembedded. It will generate a fitImage, that 
we put into an ext4 partition, from there we bootm the stuff after 
loading fitImage into RAM. This basically works, *but* small changes 
(i.e. "random" changing a kernel config parameter, rebuild with slightly 
other toolchain) will lead to a failed boot, meaning, that we get no 
output whatsoever after

Starting kernel ...

Which puzzles me a lot, since I change only parameters, that should at 
least make the Kernel print its first lines. I suspect, that something 
goes wrong on initialization of the kernel.

I do not expect that anyone can reproduce and fix the bug for me, but 
maybe, you can give me some hints how I can approach to debug this. I do 
not have a hardware debugger, so it is pretty much printk debugging...

Thanks and Regards,

    Matthias
-- 
Dr.-Ing. Matthias Schöpfer
matthias.schoepfer at googlemail.com