1：上一節講到start.S中進行了一系列的SoC相關硬件初始化以后進行了長跳轉到start_armboot 函數中；
start_armboot進一步初始化board中硬件，並設置了uboot下的命令行、環境變量、基本命令、跳轉到kernel
下面詳細介紹start_armboot中的代碼：
------------------------第一段代碼---------------------------------------------
紅色代碼為條件編譯以后要執行的代碼
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 */ //這段是c語言內嵌匯編，為了實現內存牆； 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 }
-------------------未完待續------------------------
首先看一下
init_fnc_t **init_fnc_ptr;這個變量，這是一個init_fnc_t 類型的二重指針；typedef int (init_fnc_t) (void);
可以看出init_fnc_t類型為 返回值為int 傳參為空的函數類型，看一下下面這段代碼：對
init_fnc_ptr 賦值為init_sequence（init_sequence為一個函數指針數組，這個數字為一個全局變量，存放的是硬件初始化有關的
一些函數這些函數類型都是init_fnc_t類型），因此下面for循環的作用就是遍歷init_sequence數組中的所有函數，並執行這些函數；
如果這些初始化函數的返回值為0的話則執行hang() 掛起函數；hang函數的作用是輸出
puts ("### ERROR ### Please RESET the board ###\n");並進入一個死循環；
總結一下：這段代碼是初始化一個全局變量數組，數組中存放一些硬件初始化相關的函數指針，遍歷這些函數，並進行相應硬件的初始化；這些全局變量放在數據段；
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 }
下面這段代碼是為gd_base、gd_bd、兩個全局變量分配內存地址；gd_t類型為結構體其中的內容為：大小為36byte；
{
bd_t 類型指針 //4字節
flag 無符號整形 //4字節
baudrate 波特率 無符號整形 //4字節
have_console 無符號整形 //4字節
reloc_off; /* Relocation Offset */ //4字節
env_addr //4字節
env_valid //4字節
unsigned long fb_base LCD的內存基地址 //4字節
void **jt; /* jump table */ //指針4字節
}
bd_t 也為一結構體，大小為42字節
{
int 波特率 //4字節
unsigned int IP地址 //4字節
unsigned char 網卡地址 //6字節
環境變量指針 //4字節
機器碼 //4字節
啟動參數 //4字節
內存配置結構體 //8字節*2
}
下面這段代碼的作用：gd_base 為0x23e00000 + 0x200000 - 912K -512K - 36byte這個地址用來存放這個全局變量
同樣 bd_t 全局變量的地址設置在gd_base往下移動42byte的地址；
從這段代碼我們可以看出uboot是如何進行內存分配的；
可以看下圖：下圖為uboot中的內存；
這段代碼作的事情就是為gd_t、bd_t兩個結構體分配內存地址，並初始化gd、gd->bd指針分別指向這兩個結構體；
#define DECLARE_GLOBAL_DATA_PTR register volatile gd_t *gd asm ("r8")
gd為一個register volatile結構體指針；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 */ //這段是c語言內嵌匯編，為了實現內存牆；
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數組中有有哪些函數：
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, };
函數1：cpu_init函數；因為cpu相關的初始化已經在_start函數中做了，所以這里什么也沒有做；
1 int cpu_init (void) 2 { 3 /*
4 * setup up stacks if necessary 5 */
6 #ifdef CONFIG_USE_IRQ //這個未定義 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 }
函數2：board_init函數；這個函數中初始化了dm9000網卡，並且對gd->bd中的機器碼以及啟動參數賦值；
這里要注意一下：uboot中賦值的機器碼要和linux內核中的機器碼要一致，否則不能正常啟動；
boot參數為：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 }
函數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; //設置預分頻為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); //設置為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 }
代碼解析：
typedef vu_long S5PC11X_REG32;
S5PC11X_TIMERS：定義了一個結構體類型，把與時鍾有關的所有所有寄存器都存放在這個結構體內
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;
這句代碼的意思就是把
S5PC11X_TIMERS *const timers = S5PC11X_GetBase_TIMERS();
S5PC11X_GetBase_TIMERS函數：的作用就是把timer寄存器的基地址強制類型轉換為S5PC11X_TIMERS * 類型然后賦值給 timers變量；timers->TCFG0實際就是代表基地址右移4字節
之后的地址中的值，直接賦值相當於把0x0f00這個值放到 TCFG0對應的寄存器地址處，但是這個要注意的是，寄存器必須設置為連續的/或者一一對應的，否則會造成賦值的地址錯誤；
timers->TCFG0 = 0x0f00;
static inline S5PC11X_TIMERS * S5PC11X_GetBase_TIMERS(void) { return (S5PC11X_TIMERS *)ELFIN_TIMER_BASE;
}
剩下的代碼就和裸機的代碼一致了；TCON的timer4的相應控制為清0，設置為自動reload，並且第一次要手動載入，然后時在清0，設置reload，開啟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;
----------------------------------
函數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，環境變量整個大小為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 }
執行的是紅色的代碼：即把common.c中初始化好的default_environment地址賦值到gd->env_addr中，env_valid 賦值為1； 這里對字符串數組的初始化有些疑問？？？？？？？
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" };
---------------------------------------------------------
函數5：init_baudrate初始化波特率：從env中獲取波特率 賦值給gd->bd->bi_baudrate gd->baudrate
實現是通過以下幾個函數來實現的我們逐一來分析：
/* init_baudrate這個函數的作用就是從環境變量中讀取出波特率，從之前的波特率初始化函數看出，
實際上環境變量中的波特率就是我們在x210_sd.h頭文件中配置的波特率config_baudrate，*/
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) //simple_strtoul 把字符串tmp中的波特率轉成十進制數字； : CONFIG_BAUDRATE; return (0); }
/*這個函數的作用是讀取環境變量name 到 緩存buf中，讀取成功返回n大於0，失敗返回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') //找到對應的環境變量以后，把這個環境變量保存在buf中，並返回賦值的長度 18 ; 19 if (len == n) 20 *buf = '\0'; 21 return (n); 22 } 23 return (-1); 24 }
/*這個函數的作用是判斷環境變量是從內存還是sd卡中賦值的，然后返回index對應的環境變量中的字符*/
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); }
/* envmatch函數的作用是判斷*s1，是否和i2對應的字符串相等，如果相等返回i2，*/
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 }
/* 從內存中讀取環境變量字符，作為返回值返回 */
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 }
--------------------------------------------------------------------------------------------------
函數6：串口的初始化serial_init，因為我們在_start函數中已經初始化了串口，並打印了OK
可以看出這函數中實際是調用了serial_setbrg函數，而這個函數什么也沒有做；
1 int serial_init(void) 2 { 3 serial_setbrg(); 4
5 return (0); 6 }
1 void serial_setbrg(void) 2 { 3 DECLARE_GLOBAL_DATA_PTR; 4
5 int i; 6 for (i = 0; i < 100; i++); 7 }
--------------------------------------------------------------
函數7：console_init_f 控制台初始化函數
實際在這里只把gd中的have_console賦值為1；真正的控制台初始化函數在console_init_r函數中；
1 int console_init_f (void) 2 { 3 gd->have_console = 1; 4
5 #ifdef CONFIG_SILENT_CONSOLE 6 if (getenv("silent") != NULL) 7 gd->flags |= GD_FLG_SILENT; 8 #endif
9
10 return (0); 11 }
-------------------------------------------------------------------------
函數8：display_banner函數
實際上這個函數的作用是打印version_string字符串，和打開背光
const char version_string[] =
U_BOOT_VERSION" (" __DATE__ " - " __TIME__ ")"CONFIG_IDENT_STRING;
U_BOOT_VERSION是在makefile中自動生成的，在version_autogenerated.h中#define U_BOOT_VERSION "U-Boot 1.3.4"
__DATE__ __TIME__ 也應在是在某個腳本中生成的，然后輸出到某個頭文件包含的一個全局變量；所以或打印出 U-BOOT 1.3.4 日期 時間
1 static int display_banner (void) 2 { 3 printf ("\n\n%s\n\n", version_string); 4 debug ("U-Boot code: %08lX -> %08lX BSS: -> %08lX\n", 5 _armboot_start, _bss_start, _bss_end); 6 #ifdef CONFIG_MEMORY_UPPER_CODE /* by scsuh */
7 debug("\t\bMalloc and Stack is above the U-Boot Code.\n"); 8 #else
9 debug("\t\bMalloc and Stack is below the U-Boot Code.\n"); 10 #endif
11 #ifdef CONFIG_MODEM_SUPPORT 12 debug ("Modem Support enabled\n"); 13 #endif
14 #ifdef CONFIG_USE_IRQ 15 debug ("IRQ Stack: %08lx\n", IRQ_STACK_START); 16 debug ("FIQ Stack: %08lx\n", FIQ_STACK_START); 17 #endif
18 open_backlight();//lqm. 19 //open_gprs();
20
21 return (0); 22 }
----------------------------------------------------------------------
函數9：printf_cpuinfo 打印cpu信息，紅色代碼為要執行的代碼；
1 int print_cpuinfo(void) 2 { 3 uint set_speed; 4 uint tmp; 5 uchar result_set; 6
7 #if defined(CONFIG_CLK_533_133_100_100)
8 set_speed = 53300; 9 #elif defined(CONFIG_CLK_667_166_166_133)
10 set_speed = 66700; 11 #elif defined(CONFIG_CLK_800_200_166_133)
12 set_speed = 80000; 13 #elif defined(CONFIG_CLK_1000_200_166_133) 14 set_speed = 100000; 15 #elif defined(CONFIG_CLK_1200_200_166_133)
16 set_speed = 120000; 17 #else
18 set_speed = 100000; 19 printf("Any CONFIG_CLK_XXX is not enabled\n"); 20 #endif
21
22 tmp = (set_speed / (get_ARMCLK()/1000000)); 23 24 if((tmp < 105) && (tmp > 95)){ 25 result_set = 1; 26 } else { 27 result_set = 0; 28 } 29
30 #ifdef CONFIG_MCP_SINGLE 31 printf("\nCPU: S5PV210@%ldMHz(%s)\n", get_ARMCLK()/1000000, ((result_set == 1) ? "OK" : "FAIL")); 32 #else
33 printf("\nCPU: S5PC110@%ldMHz(%s)\n", get_ARMCLK()/1000000, ((result_set == 1) ? "OK" : "FAIL")); 34 #endif
35 printf(" APLL = %ldMHz, HclkMsys = %ldMHz, PclkMsys = %ldMHz\n", 36 get_FCLK()/1000000, get_HCLK()/1000000, get_PCLK()/1000000); 37 #if 1 38 printf(" MPLL = %ldMHz, EPLL = %ldMHz\n", 39 get_MPLL_CLK()/1000000, get_PLLCLK(EPLL)/1000000); 40 printf(" HclkDsys = %ldMHz, PclkDsys = %ldMHz\n", 41 get_HCLKD()/1000000, get_PCLKD()/1000000); 42 printf(" HclkPsys = %ldMHz, PclkPsys = %ldMHz\n", 43 get_HCLKP()/1000000, get_PCLKP()/1000000); 44 printf(" SCLKA2M = %ldMHz\n", get_SCLKA2M()/1000000); 45 #endif 46 puts("Serial = CLKUART "); 47
48 return 0; 49 }
包含了一下幾個函數：get_ARMCLK函數、get_PLLCLK函數。
/*這個函數是查看時鍾域24MHz經過APLL倍頻以后，在經過分頻器以后獲得的cpu的頻率
詳細代碼分析可以看時鍾哪個章節*/
1 ulong get_ARMCLK(void) 2 { 3 ulong div,apll_ratio; 4
5 div = CLK_DIV0_REG; 6 apll_ratio = ((div>>0) & 0x7); 7
8 return ((get_PLLCLK(APLL)) / (apll_ratio + 1)); 9
10 }
/*這個函數用來獲取PLL倍頻以后的時鍾頻率：APLL、MPLL、 EPLL
詳細代碼分析可以看裸機中時鍾那一章節*/
1 static ulong get_PLLCLK(int pllreg) 2 { 3 ulong r, m, p, s; 4 5 if (pllreg == APLL) { 6 r = APLL_CON0_REG; 7 m = (r>>16) & 0x3ff; 8 } else if (pllreg == MPLL) { 9 r = MPLL_CON_REG; 10 m = (r>>16) & 0x3ff; 11 } else if (pllreg == EPLL) { 12 r = EPLL_CON_REG; 13 m = (r>>16) & 0x1ff; 14 } else 15 hang(); 16 17 p = (r>>8) & 0x3f; 18 s = r & 0x7; 19 20 if (pllreg == APLL) 21 s= s-1; 22 23 return (m * (CONFIG_SYS_CLK_FREQ / (p * (1 << s)))); 24 }
同樣可以分析其他輸出信息：最后的輸出信息如下：
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函數10：checkboard：打印board信息
1 int checkboard(void) 2 { 3 #ifdef CONFIG_MCP_SINGLE 4 #if defined(CONFIG_VOGUES)
5 printf("\nBoard: VOGUESV210\n"); 6 #else
7 printf("\nBoard: X210\n"); 8 #endif //CONFIG_VOGUES
9 #else
10 printf("\nBoard: X210\n"); 11 #endif
12 return (0); 13 }
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函數11：dram_init實際執行的一下紅色代碼：實際真正的初始化函數已經在_start函數中執行了，而這里只是把dram的信息賦值到全局變量gd->bd中；
把chip1的首地址和大小以及chip2的首地址和大小放入全局變量中；
1 int dram_init(void) 2 { 3 DECLARE_GLOBAL_DATA_PTR; 4 5 gd->bd->bi_dram[0].start = PHYS_SDRAM_1; 6 gd->bd->bi_dram[0].size = PHYS_SDRAM_1_SIZE; 7 8 #if defined(PHYS_SDRAM_2) 9 gd->bd->bi_dram[1].start = PHYS_SDRAM_2; 10 gd->bd->bi_dram[1].size = PHYS_SDRAM_2_SIZE; 11 #endif
12
13 #if defined(PHYS_SDRAM_3)
14 gd->bd->bi_dram[2].start = PHYS_SDRAM_3; 15 gd->bd->bi_dram[2].size = PHYS_SDRAM_3_SIZE; 16 #endif
17
18 return 0; 19 }
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函數12：display_dram_config實際執行的為紅色部分代碼
1 static int display_dram_config (void) 2 { 3 int i; 4
5 #ifdef DEBUG 6 puts ("RAM Configuration:\n"); 7
8 for(i=0; i<CONFIG_NR_DRAM_BANKS; i++) { 9 printf ("Bank #%d: %08lx ", i, gd->bd->bi_dram[i].start); 10 print_size (gd->bd->bi_dram[i].size, "\n"); 11 } 12 #else
13 ulong size = 0; 14 //這段代碼的作用就是計算chip1、chip2一共多少內存並輸出出來 15 for (i=0; i<CONFIG_NR_DRAM_BANKS; i++) { 16 size += gd->bd->bi_dram[i].size; 17 } 18 19 puts("DRAM: "); 20 print_size(size, "\n"); 21 #endif
22
23 return (0); 24 }
輸出內容如下： 