Boot Linux FIT image from SPL

[Sven Schwermer]

Hi,

I was wondering whether it's possible to boot a Linux FIT image (kernel 
zImage, DTB, initramfs) straight from SPL? Specifically, I'm trying to 
reduce the boot time when booting into a tiny Linux with RAM disk over 
USB SDP (i.MX6ULL). This works fine with the chain ROM -> SPL -> u-boot 
proper -> Linux. I have given it a try to boot the FIT image straight 
from SPL, but I'm getting a few (debug-level) errors:

U-Boot SPL 2021.10-00003-gc254f7c98d-dirty (Dec 27 2021 - 20:15:09 +0100)
Trying to boot from USB SDP
SDP: initialize...
SDP: handle requests...
Downloading file of size 2440036 to 0x81000000... done
Jumping to header at 0x81000000
Header Tag is not an IMX image
Found header at 0x81000000
fit read sector 0, sectors=2440036, dst=88302888, count=2440036, 
size=0x253b64
cannot find property 'firmware': -1
kernel: 'kernel-1'
Embedded data: dst=82000000, size=13caf0
Image OS is Linux
fdt: 'fdt-imx6ull-myir-mys-6ulx-eval.dtb'
Embedded data: dst=8213caf0, size=64f7
cannot find property 'loadables': -1

The "loadables" config property seems to be specific to the u-boot 
proper FIT image. I have consulted the falcon-mode readme, but it 
doesn't mention FIT images which leads me to believe that this is not an 
intended use case?

Best regards,
Sven