uboot启动kernel

基于上篇文章，将开发板烧录loder和system镜像，即可开机进console。

我们将系统停到uboot命令行，printenv看下环境变量

=> printenv
arch=arm
baudrate=1500000
board=evb_rk3399
board_name=evb_rk3399
boot_a_script=load ${
   devtype} ${
   devnum}:${
   distro_bootpart} ${
   scriptaddr} ${
   prefix}${
   script}; source ${
   scriptaddr}
boot_efi_binary=load ${
   devtype} ${
   devnum}:${
   distro_bootpart} ${
   kernel_addr_r} efi/boot/bootaa64.efi; if fdt addr ${
   fdt_addr_r}; then bootefi ${
   kernel_addr_r} ${
   fdt_addr_r};else bootefi ${
   kernel_addr_r} ${
   fdtcontroladdr};fi
boot_extlinux=sysboot ${
   devtype} ${
   devnum}:${
   distro_bootpart} any ${
   scriptaddr} ${
   prefix}extlinux/extlinux.conf
boot_net_usb_start=usb start
boot_prefixes=/ /boot/
boot_script_dhcp=boot.scr.uimg
boot_scripts=boot.scr.uimg boot.scr
boot_targets=mmc1 mmc0 usb0 pxe dhcp
bootargs=storagemedia=emmc androidboot.mode=emmc
bootcmd=run distro_bootcmd;boot_android ${
   devtype} ${
   devnum};bootrkp;
bootcmd_dhcp=run boot_net_usb_start; if dhcp ${
   scriptaddr} ${
   boot_script_dhcp}; then source ${
   scriptaddr}; fi;setenv efi_fdtfile ${
   fdtfile}; setenv efi_old_vci ${
   bootp_vci};setenv efi_old_arch ${
   bootp_arch};setenv bootp_vci PXEClient:Arch:00011:UNDI:003000;setenv bootp_arch 0xb;if dhcp ${
   kernel_addr_r}; then tftpboot ${
   fdt_addr_r} dtb/${
   efi_fdtfile};if fdt addr ${
   fdt_addr_r}; then bootefi ${
   kernel_addr_r} ${
   fdt_addr_r}; else bootefi ${
   kernel_addr_r} ${
   fdtcontroladdr};fi;fi;setenv bootp_vci ${
   efi_old_vci};setenv bootp_arch ${
   efi_old_arch};setenv efi_fdtfile;setenv efi_old_arch;setenv efi_old_vci;
bootcmd_mmc0=setenv devnum 0; run mmc_boot
bootcmd_mmc1=setenv devnum 1; run mmc_boot
bootcmd_pxe&#