u-boot2011.09 u-boot.img 的流程跟踪

• 一、主要是start.S 里面的 board_init_f 以及 board_init_r 函数分析，MLO与 u-boot.omg 的区别就在这里

* ### 二、 MLO 加载完毕，他会重新回到 start.S 重新开始
* ### 三、 board_init_f 函数的实现在 arch/arm/lib/board.c 里面
```c
264 void board_init_f(ulong bootflag)
265 {
266 bd_t *bd;
267 init_fnc_t **init_fnc_ptr;
268 gd_t *id;
269 ulong addr, addr_sp;
270
271
272 /* Pointer is writable since we allocated a register for it */
273 gd = (gd_t *) ((CONFIG_SYS_INIT_SP_ADDR) & ~0x07);
274 /* compiler optimization barrier needed for GCC >= 3.4 */
275 __asm__ __volatile__("": : :"memory");
276
277 memset((void *)gd, 0, sizeof(gd_t));
278
279 gd->mon_len = _bss_end_ofs;
280 // 这里有一个函数指针数组，里面包含很多初始化
281 for (init_fnc_ptr = init_sequence; *init_fnc_ptr; ++init_fnc_ptr) {
282 if ((*init_fnc_ptr)() != 0) {
283 hang ();
284 }
285 }
// ... ...
412 gd->bd->bi_baudrate = gd->baudrate;
413 /* Ram ist board specific, so move it to board code ... */
414 dram_init_banksize();
415 display_dram_config(); /* and display it */
416
417 gd->relocaddr = addr;
418 gd->start_addr_sp = addr_sp;
419 gd->reloc_off = addr - _TEXT_BASE;
420 debug("relocation Offset is: %08lx\n", gd->reloc_off);
421 memcpy(id, (void *)gd, sizeof(gd_t));
422
423 relocate_code(addr_sp, id, addr); // 最后回到 start.S 然后又到了 board_init_r
424
425 /* NOTREACHED - relocate_code() does not return */
426 }
```
* ### 接上函数指针数组 init_sequence
```c
235 init_fnc_t *init_sequence[] = {
236 #if defined(CONFIG_ARCH_CPU_INIT)
237 arch_cpu_init, /* basic arch cpu dependent setup */
238 #endif
239 #if defined(CONFIG_BOARD_EARLY_INIT_F)
240 board_early_init_f,
241 #endif
242 timer_init, /* initialize timer */
243 #ifdef CONFIG_FSL_ESDHC
244 get_clocks,
245 #endif
246 env_init, /* initialize environment */
247 init_baudrate, /* initialze baudrate settings */
248 serial_init, /* serial communications setup */
249 console_init_f, /* stage 1 init of console */
250 display_banner, /* say that we are here */
251 #if defined(CONFIG_DISPLAY_CPUINFO)
252 print_cpuinfo, /* display cpu info (and speed) */
253 #endif
254 #if defined(CONFIG_DISPLAY_BOARDINFO)
255 checkboard, /* display board info */
256 #endif
257 #if defined(CONFIG_HARD_I2C) || defined(CONFIG_SOFT_I2C)
258 init_func_i2c,
259 #endif
260 dram_init, /* configure available RAM banks */
261 NULL,
262 };
```


* ### 三、board_init_r 也在 arch/arm/lib/board.c
```c
443 void board_init_r(gd_t *id, ulong dest_addr)
444 {
445 char *s;
446 bd_t *bd;
447 ulong malloc_start;
448 #if !defined(CONFIG_SYS_NO_FLASH)
449 ulong flash_size;
450 #endif
451
452
453 gd = id;
454 bd = gd->bd;
455
456 gd->flags |= GD_FLG_RELOC; /* tell others: relocation done */
457
458 monitor_flash_len = _end_ofs;
459
460 /* Enable caches */
461 enable_caches();
462
463 debug("monitor flash len: %08lX\n", monitor_flash_len);
464 board_init(); /* Setup chipselects */
465
466 #ifdef CONFIG_SERIAL_MULTI
467 serial_initialize();
468
469 #endif
81 /* The Malloc area is immediately below the monitor copy in DRAM */
482 malloc_start = dest_addr - TOTAL_MALLOC_LEN;
483 mem_malloc_init (malloc_start, TOTAL_MALLOC_LEN);
484
485 stdio_init(); /* get the devices list going. */
486
487 puts("zengjf :\n");
523 #if defined(CONFIG_CMD_NAND)
524 puts("NAND : ");
525 nand_init(); /* go init the NAND */
526 #endif
// ... ...
531
532 #ifdef CONFIG_GENERIC_MMC
533 puts("MMC: ");
534 mmc_initialize(bd);
535 #endif
// .. ...
559
560 console_init_r(); /* fully init console as a device */
561
566 #if defined(CONFIG_MISC_INIT_R)
567 /* miscellaneous platform dependent initialisations */
568 misc_init_r();
569 #endif

// ... ...
649     for (;;) {
650         main_loop();
651     }
652
653     /* NOTREACHED - no way out of command loop except booting */
654 }

* ### u-boot 加载 kernel 参考：
    http://www.cnblogs.com/chenfulin5/p/6937334.html

* ### MLO 的流程参考：
    http://www.cnblogs.com/chenfulin5/p/8398399.html