Starting from [[Axel_Embedded_Linux_Kit_(XELK)#XELK_3.5.0|XELK 3.5.0]] binary version, u-boot supports the [https://en.wikipedia.org/wiki/Booting#SPL SPL] first-stage bootloader and second-stage bootloader (the proper u-boot complete binary).
It is then required to update the u-boot con on AXEL LITE SoM using some new u-boot environment variables: those vars will be present and ready to be used on the new SPL default environment.
Here below, you can find a '''step-by-step''' user's guide for updating u-boot to the new SPL version.
=== update u-boot on NAND flash ===
The SPL and u-boot image, must be flashed on NAND using the NXP <code>kobs-ng</code> utility. This tool is required for writing correct information needed by bootrom to identify the NAND as a boot device.
'''N.B.''' for programming the second stage, the <code>nandwrite</code> command has to identify a proper mtd part witch correct size. For this reason, the ''mtdparts'' variable has to be modified for writing the complete u-boot image.
The following steps are therefore necessary:
# execute '''kobs-ng''' passing the parameters for flashing the SPL on NAND
# execute '''nandwrite''' to flash uboot image on NAND