How to Update U-Boot on imx6ulz_smm_m2 board
--------------------------------------------

Required software on the host PC:

- UUU: https://github.com/NXPmicro/mfgtools

Build U-Boot for m2:

$ make mrproper
$ make imx6ulz_smm_m2_defconfig
$ make

This generates the SPL and u-boot-dtb.img binaries.

1. Loading U-Boot via USB Serial Download Protocol

Copy SPL and u-boot-dtb.img to the uuu folder.

Load the U-Boot via USB:

$ sudo uuu -v -b nand_script.lst u-boot-with-spl.imx

where nand_script.lst contains the following:

uuu_version 1.2.39

# @_flash.bin            | bootloader
# @_image   [_flash.bin] | image burn to nand, default is the same as bootloader

# This command will be run when i.MX6/7 i.MX8MM, i.MX8MQ
SDP: boot -f _flash.bin

# This command will be run when ROM support stream mode
# i.MX8QXP, i.MX8QM
SDPS: boot -f _flash.bin

# These commands will be run when use SPL and will be skipped if no spl
# SDPU will be deprecated. please use SDPV instead of SDPU
# {
SDPU: delay 1000
SDPU: write -f _flash.bin -offset 0x57c00
SDPU: jump
# }

# These commands will be run when use SPL and will be skipped if no spl
# if (SPL support SDPV)
# {
SDPV: delay 1000
SDPV: write -f _flash.bin -offset 0x11000
SDPV: jump
# }

FB: ucmd setenv fastboot_buffer ${loadaddr}
FB: download -f _image
FB: ucmd if test ! -n "$fastboot_bytes"; then setenv fastboot_bytes $filesize; else true; fi
# Burn image to nandfit partition if needed
FB: ucmd if env exists nandfit_part; then nand erase.part nandfit; nand write ${fastboot_buffer} nandfit ${fastboot_bytes}; else true; fi;
FB: ucmd nandbcb init ${fastboot_buffer} nandboot ${fastboot_bytes}
FB: Done

Then U-Boot starts and its messages appear in the console program.

Use the default environment variables:

=> env default -f -a
=> saveenv