board_init_f在/u-boot-2018.07-fmxx/arch/arm/mach-fmxx/spl.c中定义
board_init_f
u-boot-2018.07-fmxx/arch/arm/lib/crt0.S
来仔细分析如下代码：
#if ! defined(CONFIG_SPL_BUILD) //不执行
/*
* Set up intermediate environment (new sp and gd) and call
* relocate_code(addr_moni). Trick here is that we'll return
* 'here' but relocated.
*/
ldr r0, [r9, #GD_START_ADDR_SP] /* sp = gd->start_addr_sp */
bic r0, r0, #7 /* 8-byte alignment for ABI compliance */
mov sp, r0
ldr r9, [r9, #GD_BD] /* r9 = gd->bd */
sub r9, r9, #GD_SIZE /* new GD is below bd */
adr lr, here
ldr r0, [r9, #GD_RELOC_OFF] /* r0 = gd->reloc_off */
add lr, lr, r0
#if defined(CONFIG_CPU_V7M)
orr lr, #1 /* As required by Thumb-only */
#endif
ldr r0, [r9, #GD_RELOCADDR] /* r0 = gd->relocaddr */
b relocate_code
here:
/*
* now relocate vectors
*/
bl relocate_vectors
/* Set up final (full) environment */
bl c_runtime_cpu_setup /* we still call old routine here */
#endif //#if ! defined(CONFIG_SPL_BUILD) 因为定义了CONFIG_SPL_BUILD 所以不包含上述段落
#if !defined(CONFIG_SPL_BUILD) || defined(CONFIG_SPL_FRAMEWORK) //!defined(CONFIG_SPL_BUILD)为假 defined(CONFIG_SPL_FRAMEWORK) 为真 下面代码执行
# ifdef CONFIG_SPL_BUILD //执行
/* Use a DRAM stack for the rest of SPL, if requested */
bl spl_relocate_stack_gd //common/spl/spl.c中定义
cmp r0, #0
movne sp, r0
movne r9, r0
# endif
ldr r0, =__bss_start /* this is auto-relocated! */
#ifdef CONFIG_USE_ARCH_MEMSET //执行
ldr r3, =__bss_end /* this is auto-relocated! */
mov r1, #0x00000000 /* prepare zero to clear BSS */
subs r2, r3, r0 /* r2 = memset len */
bl memset
#else //不执行
ldr r1, =__bss_end /* this is auto-relocated! */
mov r2, #0x00000000 /* prepare zero to clear BSS */
clbss_l:cmp r0, r1 /* while not at end of BSS */
#if defined(CONFIG_CPU_V7M) //不执行
itt lo
#endif
strlo r2, [r0] /* clear 32-bit BSS word */
addlo r0, r0, #4 /* move to next */
blo clbss_l
#endif // CONFIG_USE_ARCH_MEMSET
#if ! defined(CONFIG_SPL_BUILD) //不执行
bl coloured_LED_init
bl red_led_on
#endif
/* call board_init_r(gd_t *id, ulong dest_addr) */
mov r0, r9 /* gd_t */
ldr r1, [r9, #GD_RELOCADDR] /* dest_addr */
/* call board_init_r */
#if CONFIG_IS_ENABLED(SYS_THUMB_BUILD)
ldr lr, =board_init_r /* this is auto-relocated! */
bx lr
#else //执行
ldr pc, =board_init_r /* this is auto-relocated! */
#endif //CONFIG_IS_ENABLED(SYS_THUMB_BUILD)
/* we should not return here. */
#endif
ENDPROC(_main)
大概流程是
bl spl_relocate_stack_gd
bl memset //bss清零
ldr pc, =board_init_r //跳转到board_init_r
一般SPL会定义CONFIG_SPL，
在common/spl/Kconfig中
config SPL_FRAMEWORK
bool "Support SPL based upon the common SPL framework"
depends on SPL
default y
默认选中SPL_FRAMEWORK
到底使用那个函数，要看Makefile和config的值
board_init_r在common/spl/spl.c中定义 该函数中有些调用
比如spl_board_init 在/u-boot-2018.07-fmxx/arch/arm/mach-fmxx/spl.c中定义
而spl_board_init又调用了preloader_console_init在common/spl/spl.c中定义
https://blog.csdn.net/voice_shen/article/details/17373671
https://www.cnblogs.com/maxpak/p/5593019.html