imx6q u-boot 启动脚本分析

bootcmd=
run findfdt;  (1)
mmc dev ${mmcdev};  (mmc dev 2)  (2)
if mmc rescan; then     (3)
if run loadbootscript; then 
run bootscript; 
else 
if run loadimage; then  (4)
run mmcboot;        (13)
else 
run netboot; 
fi; 
fi; 
else 
run netboot; 
fi
loadimage=fatload mmc ${mmcdev}:${mmcpart} ${loadaddr} ${image} (fatload mmc 2:1 0x12000000 zImage  从第2块mmc设备的1分区 装载zImage到内存的0x12000000位置) (5)


mmcboot=
echo Booting from mmc ...;  (6)
run mmcargs;                (7)
if test ${boot_fdt} = yes || test ${boot_fdt} = try; then  (9)
if run loadfdt; then  (10)
bootz ${loadaddr} - ${fdt_addr};  (12)
else 
if test ${boot_fdt} = try; then 
bootz; 
else 
echo WARN: Cannot load the DT; 
fi; 
fi; 
else 
bootz; 
fi;
mmcargs=setenv bootargs console=${console},${baudrate} ${smp} root=${mmcroot} (setenv bootargs console=ttymxc0,115200 root=/dev/mmcblk3p2 rootwait rw)  (8)
loadfdt=fatload mmc ${mmcdev}:${mmcpart} ${fdt_addr} ${fdt_file} (fatload mmc 2:1 0x18000000 imx6q-sabresd.dtb)  (11)


findfdt=
if test $fdt_file = undefined; then 
if test $board_name = SABREAUTO && test $board_rev = MX6QP; then 
setenv fdt_file imx6qp-sabreauto.dtb; 
fi; 
if test $board_name = SABREAUTO && test $board_rev = MX6Q; then 
setenv fdt_file imx6q-sabreauto.dtb; 
fi; 
if test $board_name = SABREAUTO && test $board_rev = MX6DL; then 
setenv fdt_file imx6dl-sabreauto.dtb;
fi; 
if test $board_name = SABRESD && test $board_rev = MX6QP; then 
setenv fdt_file imx6qp-sabresd.dtb; 
fi; 
if test $board_name = SABRESD && test $board_rev = MX6Q; then 
setenv fdt_file imx6q-sabresd.dtb; 
fi; 
if test $board_name = SABRESD && test $board_rev = MX6DL; then 
setenv fdt_file imx6dl-sabresd.dtb; 
fi; 
if test $fdt_file = undefined; then 
echo WARNING: Could not determine dtb to use; 
fi; 

fi;