1：上一节讲到start.S中进行了一系列的SoC相关硬件初始化以后进行了长跳转到start_armboot 函数中；
start_armboot进一步初始化board中硬件，并设置了uboot下的命令行、环境变量、基本命令、跳转到kernel
下面详细介绍start_armboot中的代码：
------------------------第一段代码---------------------------------------------
红色代码为条件编译以后要执行的代码
1 void start_armboot (void)
2 {
3 init_fnc_t **init_fnc_ptr;
4 char *s;
5 int mmc_exist = 0;
6 #if !defined(CFG_NO_FLASH) || defined (CONFIG_VFD) || defined(CONFIG_LCD)
7 ulong size;
8 #endif
9
10 #if defined(CONFIG_VFD) || defined(CONFIG_LCD)
11 unsigned long addr;
12 #endif
13
14 #if defined(CONFIG_BOOT_MOVINAND)
15 uint *magic = (uint *) (PHYS_SDRAM_1);
16 #endif
17
18 /* Pointer is writable since we allocated a register for it */
19 #ifdef CONFIG_MEMORY_UPPER_CODE /* by scsuh */
20 ulong gd_base;
21
22 gd_base = CFG_UBOOT_BASE + CFG_UBOOT_SIZE - CFG_MALLOC_LEN - CFG_STACK_SIZE - sizeof(gd_t);
23 #ifdef CONFIG_USE_IRQ
24 gd_base -= (CONFIG_STACKSIZE_IRQ+CONFIG_STACKSIZE_FIQ);
25 #endif
26 gd = (gd_t*)gd_base;
27 #else //CONFIG_MEMORY_UPPER_CODE
28 gd = (gd_t*)(_armboot_start - CFG_MALLOC_LEN - sizeof(gd_t));
29 #endif
30
31 if (readl(INF_REG_BASE+INF_REG0_OFFSET)==0xFFAADDEE)
32 {
33 extern int gbl_silent;
34 gbl_silent = 1;
35 }
36
37 /* compiler optimization barrier needed for GCC >= 3.4 */ //这段是c语言内嵌汇编，为了实现内存墙；
38 __asm__ __volatile__("": : :"memory");
39
40 memset ((void*)gd, 0, sizeof (gd_t));
41 gd->bd = (bd_t*)((char*)gd - sizeof(bd_t));
42 memset (gd->bd, 0, sizeof (bd_t));
43
44 monitor_flash_len = _bss_start - _armboot_start;
45
46 for (init_fnc_ptr = init_sequence; *init_fnc_ptr; ++init_fnc_ptr) {
47 if ((*init_fnc_ptr)() != 0) {
48 hang ();
49 }
50 }-------------------未完待续------------------------
首先看一下
init_fnc_t **init_fnc_ptr;这个变量，这是一个init_fnc_t 类型的二重指针；typedef int (init_fnc_t) (void);可以看出init_fnc_t类型为 返回值为int 传参为空的函数类型，看一下下面这段代码：对
init_fnc_ptr 赋值为init_sequence（init_sequence为一个函数指针数组，这个数字为一个全局变量，存放的是硬件初始化有关的一些函数这些函数类型都是init_fnc_t类型），因此下面for循环的作用就是遍历init_sequence数组中的所有函数，并执行这些函数；如果这些初始化函数的返回值为0的话则执行hang() 挂起函数；hang函数的作用是输出puts ("### ERROR ### Please RESET the board ###\n");并进入一个死循环；总结一下：这段代码是初始化一个全局变量数组，数组中存放一些硬件初始化相关的函数指针，遍历这些函数，并进行相应硬件的初始化；这些全局变量放在数据段；
for (init_fnc_ptr = init_sequence; *init_fnc_ptr; ++init_fnc_ptr) {
if ((*init_fnc_ptr)() != 0) {
hang ();
}
}
1 init_fnc_t *init_sequence[] = {
2 cpu_init, /* basic cpu dependent setup */
3 #if defined(CONFIG_SKIP_RELOCATE_UBOOT)
4 reloc_init, /* Set the relocation done flag, must
5 do this AFTER cpu_init(), but as soon
6 as possible */
7 #endif
8 board_init, /* basic board dependent setup */
9 interrupt_init, /* set up exceptions */
10 env_init, /* initialize environment */
11 init_baudrate, /* initialze baudrate settings */
12 serial_init, /* serial communications setup */
13 console_init_f, /* stage 1 init of console */
14 display_banner, /* say that we are here */
15 #if defined(CONFIG_DISPLAY_CPUINFO)
16 print_cpuinfo, /* display cpu info (and speed) */
17 #endif
18 #if defined(CONFIG_DISPLAY_BOARDINFO)
19 checkboard, /* display board info */
20 #endif
21 #if defined(CONFIG_HARD_I2C) || defined(CONFIG_SOFT_I2C)
22 init_func_i2c,
23 #endif
24 dram_init, /* configure available RAM banks */
25 display_dram_config,
26 NULL,
27 };
1 void hang (void)
2 {
3 puts ("### ERROR ### Please RESET the board ###\n");
4 for (;;);
5 }
下面这段代码是为gd_base、gd_bd、两个全局变量分配内存地址；gd_t类型为结构体其中的内容为：大小为36byte；
{ bd_t 类型指针 //4字节 flag 无符号整形 //4字节 baudrate 波特率 无符号整形 //4字节 have_console 无符号整形 //4字节 reloc_off; /* Relocation Offset */ //4字节 env_addr //4字节 env_valid //4字节 unsigned long fb_base LCD的内存基地址 //4字节 void **jt; /* jump table */ //指针4字节 }
bd_t 也为一结构体，大小为42字节{ int 波特率 //4字节 unsigned int IP地址 //4字节 unsigned char 网卡地址 //6字节 环境变量指针 //4字节 机器码 //4字节 启动参数 //4字节 内存配置结构体 //8字节*2 }
下面这段代码的作用：gd_base 为0x23e00000 + 0x200000 - 912K -512K - 36byte这个地址用来存放这个全局变量
同样 bd_t 全局变量的地址设置在gd_base往下移动42byte的地址；
从这段代码我们可以看出uboot是如何进行内存分配的；
可以看下图：下图为uboot中的内存；
这段代码作的事情就是为gd_t、bd_t两个结构体分配内存地址，并初始化gd、gd->bd指针分别指向这两个结构体；
#define DECLARE_GLOBAL_DATA_PTR register volatile gd_t *gd asm ("r8")
gd为一个register volatile结构体指针；asm ("r8")意思是放在r8寄存器中；
20 ulong gd_base;
21
22 gd_base = CFG_UBOOT_BASE + CFG_UBOOT_SIZE - CFG_MALLOC_LEN - CFG_STACK_SIZE - sizeof(gd_t);
23
26 gd = (gd_t*)gd_base;
31 36
37 /* compiler optimization barrier needed for GCC >= 3.4 */ //这段是c语言内嵌汇编，为了实现内存墙；
38 __asm__ __volatile__("": : :"memory");
39
40 memset ((void*)gd, 0, sizeof (gd_t));
41 gd->bd = (bd_t*)((char*)gd - sizeof(bd_t));
42 memset (gd->bd, 0, sizeof (bd_t));
43
44 monitor_flash_len = _bss_start - _armboot_start;
1 typedef struct global_data {
2 bd_t *bd;
3 unsigned long flags;
4 unsigned long baudrate;
5 unsigned long have_console; /* serial_init() was called */
6 unsigned long reloc_off; /* Relocation Offset */
7 unsigned long env_addr; /* Address of Environment struct */
8 unsigned long env_valid; /* Checksum of Environment valid? */
9 unsigned long fb_base; /* base address of frame buffer */
10 #ifdef CONFIG_VFD
11 unsigned char vfd_type; /* display type */
12 #endif
13 #if 0
14 unsigned long cpu_clk; /* CPU clock in Hz! */
15 unsigned long bus_clk;
16 phys_size_t ram_size; /* RAM size */
17 unsigned long reset_status; /* reset status register at boot */
18 #endif
19 void **jt; /* jump table */
20 } gd_t;
1 typedef struct bd_info {
2 int bi_baudrate; /* serial console baudrate */
3 unsigned long bi_ip_addr; /* IP Address */
4 unsigned char bi_enetaddr[6]; /* Ethernet adress */
5 struct environment_s *bi_env;
6 ulong bi_arch_number; /* unique id for this board */
7 ulong bi_boot_params; /* where this board expects params */
8 struct /* RAM configuration */
9 {
10 ulong start;
11 ulong size;
12 } bi_dram[CONFIG_NR_DRAM_BANKS];
13 #ifdef CONFIG_HAS_ETH1
14 /* second onboard ethernet port */
15 unsigned char bi_enet1addr[6];
16 #endif
17 } bd_t;
下面看一下init_sequence数组中有有哪些函数：
init_fnc_t *init_sequence[] = {
cpu_init, /* basic cpu dependent setup */
#if defined(CONFIG_SKIP_RELOCATE_UBOOT)
reloc_init, /* Set the relocation done flag, must
do this AFTER cpu_init(), but as soon
as possible */
#endif
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
#if defined(CONFIG_HARD_I2C) || defined(CONFIG_SOFT_I2C)
init_func_i2c,
#endif
dram_init, /* configure available RAM banks */
display_dram_config,
NULL,
};
函数1：cpu_init函数；因为cpu相关的初始化已经在_start函数中做了，所以这里什么也没有做；
1 int cpu_init (void)
2 {
3 /*
4 * setup up stacks if necessary
5 */
6 #ifdef CONFIG_USE_IRQ //这个未定义
7 IRQ_STACK_START = _armboot_start - CFG_MALLOC_LEN - CFG_GBL_DATA_SIZE - 4;
8 FIQ_STACK_START = IRQ_STACK_START - CONFIG_STACKSIZE_IRQ;
9 #endif
10 return 0;
11 }
函数2：board_init函数；这个函数中初始化了dm9000网卡，并且对gd->bd中的机器码以及启动参数赋值；
这里要注意一下：uboot中赋值的机器码要和linux内核中的机器码要一致，否则不能正常启动；
boot参数为：0x02000000+0x100；
1 int board_init(void)
2 {
3 DECLARE_GLOBAL_DATA_PTR;
4
5
6 #ifdef CONFIG_DRIVER_DM9000
7 dm9000_pre_init();
8 #endif
9
10 gd->bd->bi_arch_number = MACH_TYPE;
11 gd->bd->bi_boot_params = (PHYS_SDRAM_1+0x100);
12
13 return 0;
14 }
函数3：interrupt_init中的初始化
1 int interrupt_init(void)
2 {
3
4 S5PC11X_TIMERS *const timers = S5PC11X_GetBase_TIMERS();
5
6 /* use PWM Timer 4 because it has no output */
7 /* prescaler for Timer 4 is 16 */
8 timers->TCFG0 = 0x0f00; //设置预分频为15 +1 = 16
9 if (timer_load_val == 0) {
10 /*
11 * for 10 ms clock period @ PCLK with 4 bit divider = 1/2
12 * (default) and prescaler = 16. Should be 10390
13 * @33.25MHz and @ 66 MHz
14 */
15 timer_load_val = get_PCLK() / (16 * 100); //设置为10ms
16 }
17
18 /* load value for 10 ms timeout */
19 lastdec = timers->TCNTB4 = timer_load_val;
20 /* auto load, manual update of Timer 4 */
21 timers->TCON = (timers->TCON & ~0x00700000) | TCON_4_AUTO | TCON_4_UPDATE;
22 /* auto load, start Timer 4 */
23 timers->TCON = (timers->TCON & ~0x00700000) | TCON_4_AUTO | COUNT_4_ON;
24 timestamp = 0;
25
26
27 return (0);
28 }
代码解析：
typedef vu_long S5PC11X_REG32;
S5PC11X_TIMERS：定义了一个结构体类型，把与时钟有关的所有所有寄存器都存放在这个结构体内
typedef struct {
S5PC11X_REG32 TCFG0;
S5PC11X_REG32 TCFG1;
S5PC11X_REG32 TCON;
S5PC11X_TIMER ch[4];
S5PC11X_REG32 TCNTB4;
S5PC11X_REG32 TCNTO4;
} /*__attribute__((__packed__))*/ S5PC11X_TIMERS;
这句代码的意思就是把
S5PC11X_TIMERS *const timers = S5PC11X_GetBase_TIMERS();
S5PC11X_GetBase_TIMERS函数：的作用就是把timer寄存器的基地址强制类型转换为S5PC11X_TIMERS * 类型然后赋值给 timers变量；timers->TCFG0实际就是代表基地址右移4字节
之后的地址中的值，直接赋值相当于把0x0f00这个值放到 TCFG0对应的寄存器地址处，但是这个要注意的是，寄存器必须设置为连续的/或者一一对应的，否则会造成赋值的地址错误；
timers->TCFG0 = 0x0f00;
static inline S5PC11X_TIMERS * S5PC11X_GetBase_TIMERS(void)
{
return (S5PC11X_TIMERS *)ELFIN_TIMER_BASE;}
剩下的代码就和裸机的代码一致了；TCON的timer4的相应控制为清0，设置为自动reload，并且第一次要手动载入，然后时在清0，设置reload，开启timer4
timers->TCON = (timers->TCON & ~0x00700000) | TCON_4_AUTO | TCON_4_UPDATE; 22 /* auto load, start Timer 4 */ 23 timers->TCON = (timers->TCON & ~0x00700000) | TCON_4_AUTO | COUNT_4_ON;
---------------------------------- 函数4：env_init
1 int env_init(void)
2 {
3 #if defined(ENV_IS_EMBEDDED)
4 ulong total;
5 int crc1_ok = 0, crc2_ok = 0;
6 env_t *tmp_env1, *tmp_env2;
7
8 total = CFG_ENV_SIZE; // tatal = 0x4000 16k的大小，环境变量整个大小为16k
9
10 tmp_env1 = env_ptr;
11 tmp_env2 = (env_t *)((ulong)env_ptr + CFG_ENV_SIZE);
12
13 crc1_ok = (crc32(0, tmp_env1->data, ENV_SIZE) == tmp_env1->crc);
14 crc2_ok = (crc32(0, tmp_env2->data, ENV_SIZE) == tmp_env2->crc);
15
16 if (!crc1_ok && !crc2_ok)
17 gd->env_valid = 0;
18 else if(crc1_ok && !crc2_ok)
19 gd->env_valid = 1;
20 else if(!crc1_ok && crc2_ok)
21 gd->env_valid = 2;
22 else {
23 /* both ok - check serial */
24 if(tmp_env1->flags == 255 && tmp_env2->flags == 0)
25 gd->env_valid = 2;
26 else if(tmp_env2->flags == 255 && tmp_env1->flags == 0)
27 gd->env_valid = 1;
28 else if(tmp_env1->flags > tmp_env2->flags)
29 gd->env_valid = 1;
30 else if(tmp_env2->flags > tmp_env1->flags)
31 gd->env_valid = 2;
32 else /* flags are equal - almost impossible */
33 gd->env_valid = 1;
34 }
35
36 if (gd->env_valid == 1)
37 env_ptr = tmp_env1;
38 else if (gd->env_valid == 2)
39 env_ptr = tmp_env2;
40 #else /* ENV_IS_EMBEDDED */
41 gd->env_addr = (ulong)&default_environment[0];
42 gd->env_valid = 1;
43 #endif /* ENV_IS_EMBEDDED */
44
45 return (0);
46 }
执行的是红色的代码：即把common.c中初始化好的default_environment地址赋值到gd->env_addr中，env_valid 赋值为1； 这里对字符串数组的初始化有些疑问？？？？？？？
uchar default_environment[] = {
#endif
#ifdef CONFIG_BOOTARGS
"bootargs=" CONFIG_BOOTARGS "\0"
#endif
#ifdef CONFIG_BOOTCOMMAND
"bootcmd=" CONFIG_BOOTCOMMAND "\0"
#endif
。。。。。。。。。。。。。。。。。。。。。
#ifdef CONFIG_CLOCKS_IN_MHZ
"clocks_in_mhz=1\0"
#endif
#if defined(CONFIG_PCI_BOOTDELAY) && (CONFIG_PCI_BOOTDELAY > 0)
"pcidelay=" MK_STR(CONFIG_PCI_BOOTDELAY) "\0"
#endif
#ifdef CONFIG_EXTRA_ENV_SETTINGS
CONFIG_EXTRA_ENV_SETTINGS
#endif
"\0"
};
---------------------------------------------------------
函数5：init_baudrate初始化波特率：从env中获取波特率 赋值给gd->bd->bi_baudrate gd->baudrate
实现是通过以下几个函数来实现的我们逐一来分析：
static int init_baudrate (void)
{
char tmp[64]; /* long enough for environment variables */
int i = getenv_r ("baudrate", tmp, sizeof (tmp));
gd->bd->bi_baudrate = gd->baudrate = (i > 0)
? (int) simple_strtoul (tmp, NULL, 10)
: CONFIG_BAUDRATE;
return (0);
}
/*这个函数的作用是读取环境变量name 到 缓存buf中，读取成功返回n大于0，失败返回0*/ 1 int getenv_r (char *name, char *buf, unsigned len)
2 {
3 int i, nxt;
4
5 for (i=0; env_get_char(i) != ‘\0‘; i=nxt+1) {
6 int val, n;
7
8 for (nxt=i; env_get_char(nxt) != ‘\0‘; ++nxt) {
9 if (nxt >= CFG_ENV_SIZE) {
10 return (-1);
11 }
12 }
13 if ((val=envmatch((uchar *)name, i)) < 0)
14 continue;
15 /* found; copy out */
16 n = 0;
17 while ((len > n++) && (*buf++ = env_get_char(val++)) != ‘\0‘)
18 ;
19 if (len == n)
20 *buf = ‘\0‘;
21 return (n);
22 }
23 return (-1);
24 }
uchar env_get_char (int index)
{
uchar c;
/* if relocated to RAM */
if (gd->flags & GD_FLG_RELOC)
c = env_get_char_memory(index);
else
c = env_get_char_init(index);
return (c);
}
1 int envmatch (uchar *s1, int i2)
2 {
3
4 while (*s1 == env_get_char(i2++))
5 if (*s1++ == ‘=‘)
6 return(i2);
7 if (*s1 == ‘\0‘ && env_get_char(i2-1) == ‘=‘)
8 return(i2);
9 return(-1);
10 }
1 uchar env_get_char_memory (int index)
2 {
3 if (gd->env_valid) {
4 return ( *((uchar *)(gd->env_addr + index)) );
5 } else {
6 return ( default_environment[index] );
7 }
8 }
时间： 2024-10-16 17:14:06