I went through the instructions to build my own boot image using buildroot.
That was fairly straightforward – I was somewhat surprised that I ended up building somewhat ancient software (gcc-7.2, kernel 4.15-rc6, …), but that is probably what was working well enough a year ago …
However, I ran into (at least) one problem:
Unlike with the original image, the Cadence network adapter does not seem to work.
Specifically I see in the kernel messages:
[ 0.420000] macb 10090000.ethernet: failed to get macb_clk (4294966779)
and I also wonder whether there is a more generic problem detecting clocks
[ 0.370000] of_fixed_factor_clk: probe of soc:tlclk failed with error -12
I had networking working with the original image actually, though I have carelessly overwritten it meanwhile