uboot源码分析二

uboot的最终目标：

1.从flash读出内核——>能支持norflash 或者nandflash（他们的作用相当于电脑的硬盘）。

2.启动内核

接着上一篇的start_armboot开始分析，我们跟踪这个函数可以定位到lib_arm/board.c文件中：

看一下这一篇uboot的流程图先有个大概的方向：

void start_armboot (void)
{
init_fnc_t **init_fnc_ptr;
char *s;
#ifndef CFG_NO_FLASH
ulong size;
#endif
#if defined(CONFIG_VFD) || defined(CONFIG_LCD)
unsigned long addr;
#endif
/* Pointer is writable since we allocated a register for it */
gd = (gd_t*)(_armboot_start - CFG_MALLOC_LEN - sizeof(gd_t));
/* compiler optimization barrier needed for GCC >= 3.4 */
__asm__ __volatile__("": : :"memory");
memset ((void*)gd, 0, sizeof (gd_t));
gd->bd = (bd_t*)((char*)gd - sizeof(bd_t));
memset (gd->bd, 0, sizeof (bd_t));
monitor_flash_len = _bss_start - _armboot_start;
for (init_fnc_ptr = init_sequence; *init_fnc_ptr; ++init_fnc_ptr) {
if ((*init_fnc_ptr)() != 0) {
hang ();
}
}
/*其中上面的init_sequence 函数我能们可以跟踪到各种初始化操作。
 * init_fnc_t *init_sequence[] = {
 * cpu_init, /* basic cpu dependent setup */
 * board_init,/* basic board dependent setup */
 * interrupt_init,/* set up exceptions */
 * env_init, /* initialize environment */
 * init_baudrate,/* initialze baudrate settings */
 * serial_init,/* serial communications setup */
 * console_init_f,/* stage 1 init of console */
 * display_banner,/* say that we are here */
 * #if defined(CONFIG_DISPLAY_CPUINFO)
 * print_cpuinfo,/* display cpu info (and speed) */
 * #endif
 * #if defined(CONFIG_DISPLAY_BOARDINFO)
 * checkboard,/* display board info */
 * #endif
 * dram_init, /* configure available RAM banks */
 * display_dram_config,
 * NULL,
 *  };
 *
 */

/*cpu_init:这些分配出来的内存都对应uboot一中的那副图。
 * int cpu_init (void)
 * {
 * /*
 * * setup up stacks if necessary
 * */
 * #ifdef CONFIG_USE_IRQ    //_armboot_start = 0x33f50000
 * IRQ_STACK_START = _armboot_start - CFG_MALLOC_LEN - CFG_GBL_DATA_SIZE - 4;
 * FIQ_STACK_START = IRQ_STACK_START - CONFIG_STACKSIZE_IRQ;
 *      FREE_RAM_END = FIQ_STACK_START - CONFIG_STACKSIZE_FIQ - CONFIG_STACKSIZE;
 *      FREE_RAM_SIZE = FREE_RAM_END - PHYS_SDRAM_1;
 * #else    
 *      FREE_RAM_END = _armboot_start - CFG_MALLOC_LEN - CFG_GBL_DATA_SIZE - 4 - CONFIG_STACKSIZE;
 *      FREE_RAM_SIZE = FREE_RAM_END - PHYS_SDRAM_1;
 * #endif
 * return 0;
 * }
 */
#if 0

int board_init (void)
{
    S3C24X0_CLOCK_POWER * const clk_power = S3C24X0_GetBase_CLOCK_POWER();
    S3C24X0_GPIO * const gpio = S3C24X0_GetBase_GPIO();
    //管脚的设置。
    /* set up the I/O ports */ 
    gpio->GPACON = 0x007FFFFF;
    gpio->GPBCON = 0x00044555;
    gpio->GPBUP = 0x000007FF;
    gpio->GPCCON = 0xAAAAAAAA;
    gpio->GPCUP = 0x0000FFFF;
    gpio->GPDCON = 0xAAAAAAAA;
    gpio->GPDUP = 0x0000FFFF;
    gpio->GPECON = 0xAAAAAAAA;
    gpio->GPEUP = 0x0000FFFF;
    gpio->GPFCON = 0x000055AA;
    gpio->GPFUP = 0x000000FF;
    gpio->GPGCON = 0xFF95FFBA;
    gpio->GPGUP = 0x0000FFFF;
    gpio->GPHCON = 0x002AFAAA;
    gpio->GPHUP = 0x000007FF;
    /* support both of S3C2410 and S3C2440, by www.100ask.net */
    if (isS3C2410)
    {    //设置机器id。。
        /* arch number of SMDK2410-Board */
        gd->bd->bi_arch_number = MACH_TYPE_SMDK2410;
    }
    else
    {
        /* arch number of SMDK2440-Board */
        gd->bd->bi_arch_number = MACH_TYPE_S3C2440;
    }
       //设置boot参数
    /* adress of boot parameters */
    gd->bd->bi_boot_params = 0x30000100;
#if 0
    icache_enable();
    dcache_enable();
#endif
    return 0;
}
#endif
#ifndef CFG_NO_FLASH
/* configure available FLASH banks */
size = flash_init (); //对norflash的初始化
display_flash_config (size);
#endif /* CFG_NO_FLASH */
#ifdef CONFIG_VFD
# ifndef PAGE_SIZE
#  define PAGE_SIZE 4096
# endif
/*
* reserve memory for VFD display (always full pages)
*/
/* bss_end is defined in the board-specific linker script */
addr = (_bss_end + (PAGE_SIZE - 1)) & ~(PAGE_SIZE - 1);
size = vfd_setmem (addr);
gd->fb_base = addr;
#endif /* CONFIG_VFD */

#ifdef CONFIG_LCD
# ifndef PAGE_SIZE
#  define PAGE_SIZE 4096
# endif
/*
* reserve memory for LCD display (always full pages)
*/
/* bss_end is defined in the board-specific linker script */
addr = (_bss_end + (PAGE_SIZE - 1)) & ~(PAGE_SIZE - 1);
size = lcd_setmem (addr);
gd->fb_base = addr;
#endif /* CONFIG_LCD */
/* armboot_start is defined in the board-specific linker script */
        // 分配出192k的空间，为uboot一的192k分配出来的空间
mem_malloc_init (_armboot_start - CFG_MALLOC_LEN);
#if (CONFIG_COMMANDS & CFG_CMD_NAND)
puts ("NAND:  ");
nand_init(); /* go init the NAND */
#endif
#ifdef CONFIG_HAS_DATAFLASH
AT91F_DataflashInit();
dataflash_print_info();
#endif
/* initialize environment */
env_relocate (); //环境变量的初始化
#ifdef CONFIG_VFD
/* must do this after the framebuffer is allocated */
drv_vfd_init();
#endif /* CONFIG_VFD */
/* IP Address */
gd->bd->bi_ip_addr = getenv_IPaddr ("ipaddr");
/* MAC Address */
{
int i;
ulong reg;
char *s, *e;
char tmp[64];
i = getenv_r ("ethaddr", tmp, sizeof (tmp));
s = (i > 0) ? tmp : NULL;
for (reg = 0; reg < 6; ++reg) {
gd->bd->bi_enetaddr[reg] = s ? simple_strtoul (s, &e, 16) : 0;
if (s)
s = (*e) ? e + 1 : e;
}
#ifdef CONFIG_HAS_ETH1
i = getenv_r ("eth1addr", tmp, sizeof (tmp));
s = (i > 0) ? tmp : NULL;
for (reg = 0; reg < 6; ++reg) {
gd->bd->bi_enet1addr[reg] = s ? simple_strtoul (s, &e, 16) : 0;
if (s)
s = (*e) ? e + 1 : e;
}
#endif
}
devices_init ();/* get the devices list going. */
#ifdef CONFIG_CMC_PU2
load_sernum_ethaddr ();
#endif /* CONFIG_CMC_PU2 */
jumptable_init ();
console_init_r ();/* fully init console as a device */
#if defined(CONFIG_MISC_INIT_R)
/* miscellaneous platform dependent initialisations */
misc_init_r ();
#endif
Port_Init();
if (!PreLoadedONRAM) {
/* enable exceptions */
enable_interrupts ();
   /* add by www.100ask.net */
   usb_init();
}
    /* Perform network card initialisation if necessary */
#ifdef CONFIG_DRIVER_CS8900
cs8900_get_enetaddr (gd->bd->bi_enetaddr);
#endif
#if defined(CONFIG_DRIVER_SMC91111) || defined (CONFIG_DRIVER_LAN91C96)
if (getenv ("ethaddr")) {
smc_set_mac_addr(gd->bd->bi_enetaddr);
}
#endif /* CONFIG_DRIVER_SMC91111 || CONFIG_DRIVER_LAN91C96 */
/* Initialize from environment */
if ((s = getenv ("loadaddr")) != NULL) {
load_addr = simple_strtoul (s, NULL, 16);
}
#if (CONFIG_COMMANDS & CFG_CMD_NET)
if ((s = getenv ("bootfile")) != NULL) {
copy_filename (BootFile, s, sizeof (BootFile));
}
#endif /* CFG_CMD_NET */
#ifdef BOARD_LATE_INIT
board_late_init ();
#endif
#if (CONFIG_COMMANDS & CFG_CMD_NET)
#if defined(CONFIG_NET_MULTI)
puts ("Net:   ");
#endif
eth_initialize(gd->bd);
#endif
/* main_loop() can return to retry autoboot, if so just run it again. */
for (;;) {
main_loop ();
}
/* NOTREACHED - no way out of command loop except booting */
}
我们从上面的代码可以看到start_armboot函数经过各种的初始化例如：
flash_init(),nand_init() 等最后来到main_loop ();
void main_loop (void)
{
#ifndef CFG_HUSH_PARSER
static char lastcommand[CFG_CBSIZE] = { 0, };
int len;
int rc = 1;
int flag;
#endif
#if defined(CONFIG_BOOTDELAY) && (CONFIG_BOOTDELAY >= 0)
char *s;
int bootdelay;
#endif
#ifdef CONFIG_PREBOOT
char *p;
#endif
#ifdef CONFIG_BOOTCOUNT_LIMIT
unsigned long bootcount = 0;
unsigned long bootlimit = 0;
char *bcs;
char bcs_set[16];
#endif /* CONFIG_BOOTCOUNT_LIMIT */
#if defined(CONFIG_VFD) && defined(VFD_TEST_LOGO)
ulong bmp = 0;/* default bitmap */
extern int trab_vfd (ulong bitmap);
#ifdef CONFIG_MODEM_SUPPORT
if (do_mdm_init)
bmp = 1; /* alternate bitmap */
#endif
trab_vfd (bmp);
#endif /* CONFIG_VFD && VFD_TEST_LOGO */
#ifdef CONFIG_BOOTCOUNT_LIMIT
bootcount = bootcount_load();
bootcount++;
bootcount_store (bootcount);
sprintf (bcs_set, "%lu", bootcount);
setenv ("bootcount", bcs_set);
bcs = getenv ("bootlimit");
bootlimit = bcs ? simple_strtoul (bcs, NULL, 10) : 0;
#endif /* CONFIG_BOOTCOUNT_LIMIT */
#ifdef CONFIG_MODEM_SUPPORT
debug ("DEBUG: main_loop:   do_mdm_init=%d\n", do_mdm_init);
if (do_mdm_init) {
char *str = strdup(getenv("mdm_cmd"));
setenv ("preboot", str);  /* set or delete definition */
if (str != NULL)
free (str);
mdm_init(); /* wait for modem connection */
}
#endif  /* CONFIG_MODEM_SUPPORT */
#ifdef CONFIG_VERSION_VARIABLE
{
extern char version_string[];
setenv ("ver", version_string);  /* set version variable */
}
#endif /* CONFIG_VERSION_VARIABLE */
#ifdef CFG_HUSH_PARSER
u_boot_hush_start ();
#endif
#ifdef CONFIG_AUTO_COMPLETE
install_auto_complete();
#endif
#ifdef CONFIG_JFFS2_CMDLINE
    extern int mtdparts_init(void);
    if (!getenv("mtdparts"))
    {
        run_command("mtdparts default", 0);
    }
    else
    {
        mtdparts_init();
    }
#endif
#ifdef CONFIG_PREBOOT
if ((p = getenv ("preboot")) != NULL) {
# ifdef CONFIG_AUTOBOOT_KEYED
int prev = disable_ctrlc(1);/* disable Control C checking */
# endif
# ifndef CFG_HUSH_PARSER
run_command (p, 0);
# else
parse_string_outer(p, FLAG_PARSE_SEMICOLON |
   FLAG_EXIT_FROM_LOOP);
# endif
# ifdef CONFIG_AUTOBOOT_KEYED
disable_ctrlc(prev);/* restore Control C checking */
# endif
}
#endif /* CONFIG_PREBOOT */
#if defined(CONFIG_BOOTDELAY) && (CONFIG_BOOTDELAY >= 0)
         // 设置"bootdelay" 把它转化为数字
s = getenv ("bootdelay");
bootdelay = s ? (int)simple_strtol(s, NULL, 10) : CONFIG_BOOTDELAY;
debug ("### main_loop entered: bootdelay=%d\n\n", bootdelay);
# ifdef CONFIG_BOOT_RETRY_TIME
init_cmd_timeout ();
# endif /* CONFIG_BOOT_RETRY_TIME */
if (PreLoadedONRAM){
printf("Use these steps to program the image to flash:\n");
printf("1. In OpenOCD\n");
printf("   Run the 'halt' command to halt u-boot\n");
printf("   Run the 'load_image <file> <address>' command to load file to SDRAM\n");
printf("   Run the 'resume' command to resume u-boot\n");
printf("2. In u-boot, use the flash commands to program the image to flash\n");
printf("Or, use the tftp or nfs command to download file, and then program the flash.\n");
goto PROMPT;
}
#ifdef CONFIG_BOOTCOUNT_LIMIT
if (bootlimit && (bootcount > bootlimit)) {
printf ("Warning: Bootlimit (%u) exceeded. Using altbootcmd.\n",
       (unsigned)bootlimit);
s = getenv ("altbootcmd");
}
else
#endif /* CONFIG_BOOTCOUNT_LIMIT */
s = getenv ("bootcmd");
debug ("### main_loop: bootcmd=\"%s\"\n", s ? s : "<UNDEFINED>");
        //如果倒计时时间内没有空格按下
if (bootdelay >= 0 && s && !abortboot (bootdelay)) {
# ifdef CONFIG_AUTOBOOT_KEYED
int prev = disable_ctrlc(1);/* disable Control C checking */
# endif       
# ifndef CFG_HUSH_PARSER
        {
            printf("Booting Linux ...\n"); 
            // bootcmd 命令：
            // nand.read.jffs 0x30007f00  kernel   //从nand读内核
            // bootm 0x30007f00                    //启动内核
       run_command (s, 0);                     
        }
# else
parse_string_outer(s, FLAG_PARSE_SEMICOLON |
   FLAG_EXIT_FROM_LOOP);
# endif
# ifdef CONFIG_AUTOBOOT_KEYED
disable_ctrlc(prev);/* restore Control C checking */
# endif
}
# ifdef CONFIG_MENUKEY
if (menukey == CONFIG_MENUKEY) {
   s = getenv("menucmd");
   if (s) {
# ifndef CFG_HUSH_PARSER
run_command (s, 0);
# else
parse_string_outer(s, FLAG_PARSE_SEMICOLON |
   FLAG_EXIT_FROM_LOOP);
# endif
   }
}
#endif /* CONFIG_MENUKEY */
#endif /* CONFIG_BOOTDELAY */
#ifdef CONFIG_AMIGAONEG3SE
{
   extern void video_banner(void);
   video_banner();
}
#endif
    run_command("menu", 0);
/*
* Main Loop for Monitor Command Processing
*/
PROMPT:
#ifdef CFG_HUSH_PARSER
parse_file_outer();
/* This point is never reached */
for (;;);
#else
for (;;) {
#ifdef CONFIG_BOOT_RETRY_TIME
if (rc >= 0) {
/* Saw enough of a valid command to
* restart the timeout.
*/
reset_cmd_timeout();
}
#endif
len = readline (CFG_PROMPT); //读串口的命令
flag = 0; /* assume no special flags for now */
if (len > 0)
strcpy (lastcommand, console_buffer);
else if (len == 0)
flag |= CMD_FLAG_REPEAT;
#ifdef CONFIG_BOOT_RETRY_TIME
else if (len == -2) {
/* -2 means timed out, retry autoboot
*/
puts ("\nTimed out waiting for command\n");
# ifdef CONFIG_RESET_TO_RETRY
/* Reinit board to run initialization code again */
do_reset (NULL, 0, 0, NULL);
# else
return; /* retry autoboot */
# endif
}
#endif
if (len == -1)
puts ("<INTERRUPT>\n");
else
rc = run_command (lastcommand, flag);
if (rc <= 0) {
/* invalid command or not repeatable, forget it */
lastcommand[0] = 0;
}
}
#endif /*CFG_HUSH_PARSER*/
}
uboot的一些核心：就是一些命令。