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

  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

  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

  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

原文地址：https://www.cnblogs.com/chenfulin5/p/8398816.html