[U-Boot] SPL loading multiple binaries from FIT image?

[Andre Przywara]

Hi,

(sorry if this has been discussed before, feel free to point me to any
existing thread then)

for the Pine64 I am looking into letting the SPL load multiple images
from a FIT image.
Looking at common/spl/spl-fit.c I see that the current SPL FIT support
just loads the first image from the "loadables" list as the U-Boot image
and then selects and loads the matching FDT right after it.
Feature-wise that seems to match what a legacy U-Boot image provides,
but I was wondering if anyone uses the multiple images feature that FIT
adds to the game?

I need to at least load another image (ARM Trusted Firmware(ATF)),
possibly the management controller firmware in the future as well.
This has to be done before the actual U-Boot starts, so from the SPL.

So I hacked the code to iterate over all images enumerated in the
"loadables" property and load them to their load addresses. That somehow
seems to work, but now I was wondering how to make this as flexible as
possible:
1) How do we know what image is for U-Boot? Shall there be a separate
"uboot" property (next to kernel, loadables, etc)? Or do we stay with
the current assumption that it's the first from the loadables list?
2) At the moment we don't honour the entry point. Is there any reason
for that?
3) Would it be feasible to load all images listed in the loadables
property and then branch to the only one (or the first) that has an
entry point property? In my case this would be ATF (which then later
drops to U-Boot at its well known load address).

I wonder if this has been discussed before and would be grateful if
people would share their opinion on the best approach. I will be happy
to post patches once we agreed on something.

Cheers,
Andre.