[U-Boot] A80 (CubieBoard4) u-boot - what to inject in boot0 area?

[Konrad Rzeszutek Wilk]

Hey,

I am trying to install an U-boot from the upstream repo as it looks to have most (if not all?)
of the features needed for the A80 board (Cubieboard4).

I've built the uboot just fine (using the default ./configs/Cubieboard4_defconfig)
..
./tools/mkimage -A arm -T firmware -C none -O u-boot -a 0x2a000000 -e 0 -n "U-Boot 2017.07-00217-ge14b116 for sunxi board" -d u-boot.bin u-boot.img 
Image Name:   U-Boot 2017.07-00217-ge14b116 fo
Created:      Wed Jul 12 22:11:53 2017
Image Type:   ARM U-Boot Firmware (uncompressed)
Data Size:    355711 Bytes = 347.37 KiB = 0.34 MiB
Load Address: 2a000000
Entry Point:  00000000

And now I am trying to load it on the SD card and load it
on a Cubieboard4, but it just hangs.

If I use from the CC-A80-binaries[*1] git repo the "sdcard-fwbuild.sh"
and put the two resulting binaries on the SD card it boots fine.

But naturally the u-boot that is on the mentioned repo is from 2011
and I would like a more recent version.

If I try to use the CC-A80-binaries[*1] git repo and the "sdcard-fwbuild.sh"
with the upstream u-boot it complains very loudly - and the resulting
binary is not created.

I figured out that it must be due to the header which as the magic
string of 'uboot' (which in [*2] is in arch/arm/cpu/armv7/sun9iw1/spare_head.c)

In u-boot upstream I can set CONFIG_RESERVE_ALLWINNER_BOOT0_HEADER=y
which I did, but now I am struggling to figure out what I am
suppose to put in there. Any ideas? Is there an tool to fill this
area out? And more importantly, am I on the right track or is
there something else that I a missing?

I did look at board/sunxi/README.sunxi64 and it explained about the boot0
but that talks about A53 boards I have an A15 (armv7) - and
'arm-trusted-firmware' is all geared towards armv8.

Hints of what I should do next?

Thanks!

[*1]: https://github.com/cubieboard/CC-A80-binaries
[*2]: https://github.com/cubieboard/CC-A80-u-boot