uboot进入kernel中间的延时时间可以通过BOOTDELAY这个宏来控制。
修改uboot/common/Kconfig文件
config BOOTDELAY
int "delay in seconds before automatically booting"
default 0
depends on AUTOBOOT
help
Delay before automatically running bootcmd;
set to 0 to autoboot with no delay, but you can stop it by key input.
set to -1 to disable autoboot.
set to -2 to autoboot with no delay and not check for abort
See doc/README.autoboot for details.
default 0 表示不延时，1表示延时1s。