Since rootfs runs in memory in fastboot mode, enough memory is required, so the default fastboot mode in the source code is for SSD202. If SSD201 is to be used, you need to modify Release_to_customer.sh:
#vi Release_to_customer.sh

In order to make the system start as fast as possible, we need to shut down time-consuming tasks or wait for the system to start before executing:
#vi project/configs/i2m/rootfs_fastboot.mk

Compile:
#./Release_to_customer.sh -f nand -p ssd201 -q fastboot
After the update is started, you can see that uboot is skipped during the boot process.