start.S stage 1: reset: set the cpu to svc32 mode disable the watchdog mask all IRQs(INTMSK, INTSUBMSK) cpu_init_crit(mmu, bus width status controller) set up the stack clock_init relocate u-boot ro RAM: copy code to RAM clear bbs setLoadFlag stage 2
4.Bootloader:u-boot.2009.08分析与移植4.1:分析u-boot根文件夹下的Makefile,能够看到uboot编译的顺序例如以下,由此可知编译运行的第一个文件是cpu/$(CPU)/start.o,又因为是基于 arm920t架构的,所以去分析cpu/arm920t/start.S源文件. # U-Boot objects....order is important (i.e. start must be first)OBJS = cpu/$(CPU)/start.o