start_armboot()函数的主要作用，其实该函数就是进行一系列的硬件初始化，然后进入main_loop，等待用户的命令，
typedef int (init_fnc_t) (void); //define init_fnc_t type
init_fnc_t *init_sequence[] = { //define point array init_sequence type's pionter
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 *///串口初始化后我们就可以打印信息了
console_init_f, /* stage 1 init of console */
display_banner, /* say that we are here */
dram_init, /* configure available RAM banks */
display_dram_config,
#if defined(CONFIG_VCMA9)
checkboard,
#endif
NULL,
};
void start_armboot (void)
{
DECLARE_GLOBAL_DATA_PTR;
ulong size;
init_fnc_t **init_fnc_ptr; ///point initial function's pointer
char *s;
#if defined(CONFIG_VFD)
unsigned long addr;
#endif
#if CFG_LED_FLASH
LED(); ///all leds power on flash once
#endif
/* Pointer is writable since we allocated a register for it */
gd = (gd_t*)(_armboot_start - CFG_MALLOC_LEN - sizeof(gd_t));
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;
///This for{} init arry init_sequence[] paraments one by one
for (init_fnc_ptr = init_sequence; *init_fnc_ptr; ++init_fnc_ptr) {
if ((*init_fnc_ptr)() != 0) {
hang ();///f init fail output "error" and go to dead cycle,if that we must reset cpu
}
}
/* configure available FLASH banks */
size = flash_init (); ///init flash source code don't understand???
display_flash_config (size); /// print flash's config information
#ifdef CONFIG_VFD ///#define CONFIG_VFD 1 in Trab.h
# ifndef PAGE_SIZE
# define PAGE_SIZE 4096 //若没定义则用4096
# endif
/*
* reserve memory for VFD display (always full pages)
*/
/* armboot_end is defined in the board-specific linker script */
addr = (_bss_start + (PAGE_SIZE - 1)) & ~(PAGE_SIZE - 1);
size = vfd_setmem (addr);
gd->fb_base = addr;
#endif /* CONFIG_VFD */
/* armboot_start is defined in the board-specific linker script */
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 ();
#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;
uchar 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;
}
}
devices_init (); /* get the devices list going. */
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
/* enable exceptions */
enable_interrupts ();
/* Perform network card initialisation if necessary */
#ifdef CONFIG_DRIVER_CS8900
cs8900_get_enetaddr (gd->bd->bi_enetaddr);
#endif
#ifdef CONFIG_DRIVER_LAN91C96
if (getenv ("ethaddr")) {
smc_set_mac_addr(gd->bd->bi_enetaddr);
}
/* eth_hw_init(); */
#endif /* 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
/* 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 */
}
void hang (void)
{
puts ("### ERROR ### Please RESET the board ###\n");
for (;;);
}
#ifdef CONFIG_MODEM_SUPPORT
/* called from main loop (common/main.c) */
extern void dbg(const char *fmt, ...);
int mdm_init (void)
{
char env_str[16];
char *init_str;
int i;
extern char console_buffer[];
static inline void mdm_readline(char *buf, int bufsiz);
extern void enable_putc(void);
extern int hwflow_onoff(int);
enable_putc(); /* enable serial_putc() */
#ifdef CONFIG_HWFLOW
init_str = getenv("mdm_flow_control");
if (init_str && (strcmp(init_str, "rts/cts") == 0))
hwflow_onoff (1);
else
hwflow_onoff(-1);
#endif
for (i = 1;;i++) {
sprintf(env_str, "mdm_init%d", i);
if ((init_str = getenv(env_str)) != NULL) {
serial_puts(init_str);
serial_puts("\n");
for(;;) {
mdm_readline(console_buffer, CFG_CBSIZE);
dbg("ini%d: [%s]", i, console_buffer);
if ((strcmp(console_buffer, "OK") == 0) ||
(strcmp(console_buffer, "ERROR") == 0)) {
dbg("ini%d: cmd done", i);
break;
} else /* in case we are originating call ... */
if (strncmp(console_buffer, "CONNECT", 7) == 0) {
dbg("ini%d: connect", i);
return 0;
}
}
} else
break; /* no init string - stop modem init */
udelay(100000);
}
udelay(100000);
/* final stage - wait for connect */
for(;i > 1;) { /* if 'i' > 1 - wait for connection
message from modem */
mdm_readline(console_buffer, CFG_CBSIZE);
dbg("ini_f: [%s]", console_buffer);
if (strncmp(console_buffer, "CONNECT", 7) == 0) {
dbg("ini_f: connected");
return 0;
}
}
return 0;
}
/* 'inline' - We have to do it fast */
static inline void mdm_readline(char *buf, int bufsiz)
{
char c;
char *p;
int n;
n = 0;
p = buf;
for(;;) {
c = serial_getc();
/* dbg("(%c)", c); */
switch(c) {
case '\r':
break;
case '\n':
*p = '\0';
return;
default:
if(n++ > bufsiz) {
*p = '\0';
return; /* sanity check */
}
*p = c;
p++;
break;
}
}
}
#endif /* CONFIG_MODEM_SUPPORT */
在介绍该函数之前，我们需要看一看几个数据结构，这些是u-boot中几个重要的数据结构：
1）、gd_t该数据结构保存了u-boot需要的配置信息，注释简单明了
typedef struct global_data {
bd_t *bd; //与板子相关的结构，见下面
unsigned long flags;
unsigned long baudrate;
unsigned long have_console; /* serial_init() was called */
unsigned long reloc_off; /* Relocation Offset */
unsigned long env_addr; /* Address of Environment struct */
unsigned long env_valid; /* Checksum of Environment valid? */
#ifdef CONFIG_VFD //我们一般没有配置这个，这个是frame buffer的首地址
unsigned long fb_base; /* base address of frame buffer */
#endif
} gd_t;
2）、bd_t 保存与板子相关的配置参数
typedef struct bd_info {
int bi_baudrate; /* serial console baudrate */
unsigned long bi_ip_addr; /* IP Address */
unsigned char bi_enetaddr[6]; /* Ethernet adress */
struct environment_s *bi_env;
ulong bi_arch_number; /* unique id for this board */
ulong bi_boot_params; /* where this board expects params */
struct /* RAM configuration */
{
ulong start;
ulong size;
} bi_dram[CONFIG_NR_DRAM_BANKS];//在我的板子上是1个
} bd_t;
现在我贴出start_armboot ()的源代码，然后具体的在其中解释一些代码的作用：
void start_armboot (void)
{
DECLARE_GLOBAL_DATA_PTR;
ulong size;
gd_t gd_data;
bd_t bd_data;
init_fnc_t **init_fnc_ptr; //这个是函数的指针，指向一些硬件初始化的函数，见下面
//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 */
// display_banner,
// dram_init, /* configure available RAM banks */
// display_dram_config,
// NULL,
// };
//printf("**********Start *************\n");
/* Pointer is writable since we allocated a register for it */
gd = &gd_data;
memset (gd, 0, sizeof (gd_t));//初始化为0
gd->bd = &bd_data;
memset (gd->bd, 0, sizeof (bd_t));//初始化为0
//注意，下面的循环是依次调用各个硬件初始化函数，顺序见上面的的数组，我们在下一篇中依次解释每种硬//件的初始化，第六个就是串口的初始化，这时候我们就可以通过串口输出信息了
for (init_fnc_ptr = init_sequence; *init_fnc_ptr; ++init_fnc_ptr) {
if ((*init_fnc_ptr)() != 0) {
hang (); //如果不成功的话，就“输出信息，然后就进入死循环”
}
}
/* configure available FLASH banks */
size = flash_init (); //flash的初始化
display_flash_config (size);//打印flash的配置信息
/* initialize environment */
env_relocate ();//环境的初始化，代码在common\env_common.c中
/* IP Address */
bd_data.bi_ip_addr = getenv_IPaddr ("ipaddr");//读取IP地址，保存到bd_t数据结构中
/* MAC Address */ //MAC地址的初始化
{
int i;
ulong reg;
char *s, *e;
uchar tmp[64];
i = getenv_r ("ethaddr", tmp, sizeof (tmp));
s = (i > 0) ? tmp : NULL;
for (reg = 0; reg < 6; ++reg) {
bd_data.bi_enetaddr[reg] = s ? simple_strtoul (s, &e, 16) : 0;
if (s)
s = (*e) ? e + 1 : e;
}
}
/* enable exceptions */ //允许中断
enable_interrupts ();
#ifdef CONFIG_DRIVER_CS8900 //配置网卡
if (!getenv ("ethaddr")) {
cs8900_get_enetaddr (gd->bd->bi_enetaddr);
}
#endif
//直接进入main_loop 该函数在common\main.c中，至此，硬件初始化完成
/* 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 */
}
