U-Boot启动过程分解 2

2.?????? 初始化函数功能：

?????? for (init_fnc_ptr = init_sequence; *init_fnc_ptr; ++init_fnc_ptr) {

????????????? if ((*init_fnc_ptr)() != 0) {

???????????????????? hang ();

????????????? }

?????? }

?????? 此处判断init_fnc_t的结构是否清零，否则打印

“### ERROR ### Please RESET the board ###n”

?

附：init_fnc_t的结构定义：

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,

};

gd_t的结构定义：

typedef???? struct????? global_data {

bd_t??????? *bd;

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? */

unsigned long? fb_base;? /* base address of frame buffer */

#ifdef CONFIG_VFD

unsigned char vfd_type; /* display type */

#endif

#if 0

unsigned long? cpu_clk;? /* CPU clock in Hz!????????????? */

unsigned long? bus_clk;

unsigned long? ram_size; /* RAM size */

unsigned long? reset_status;?? /* reset status register at boot */

#endif

void??????? **jt;??????? /* jump table */

} gd_t;

3.?????? 若定义CFG_NO_FLASH，对FLASH初始化：

初始化FLASH，并打印flash：size

此处未涉及，不再追究；

4.?????? 若定义CONFIG_VFD则对其进行初始化：

设置初始化地址，此处未涉及，不再追究；

5.?????? 若定义CONFIG_LCD对其地址初始化：

此处定义LCD页为4096，并将_bss_end 后一页空间设为其地址，并将其清零，再将地址赋值到gd->fb_base；

6.?????? 对内存地址初始化：

此处调用void mem_malloc_init(ulong dest_addr);对内存的起始、结束和断点地址设置；

#ifdef CONFIG_MEMORY_UPPER_CODE /* by scsuh */

mem_malloc_init (CFG_UBOOT_BASE + CFG_UBOOT_SIZE - CFG_MALLOC_LEN - CFG_STACK_SIZE);

#else

mem_malloc_init (_armboot_start - CFG_MALLOC_LEN);

#endif

?

附：

static

void mem_malloc_init (ulong dest_addr)

{

mem_malloc_start = dest_addr;

mem_malloc_end = dest_addr + CFG_MALLOC_LEN;

mem_malloc_brk = mem_malloc_start;

?

/* memset ((void *) mem_malloc_start,

?????????????? mem_malloc_end - mem_malloc_start); */

}

7.?????? 初始化SDCard和nand flash：

本文档只针对S3c6410+256M nand flash注释，程序在此处分别判断CONFIG_SMDK6410/CONFIG_SMDK6430、CONFIG_SMDK6400/CONFIG_SMDK2450/CONFIG_SMDK2416两类不同cpu进行不同初始化，不相关其余部分忽略；

???? /* SD/MMC detecting is on as default */

???? puts("SD/MMC:? ");

???? movi_set_capacity();??????????? /*设置容量，未作任何处理*/

???? movi_set_ofs(MOVI_TOTAL_BLKCNT);??? /*填充ofsinfo结构*/

???? movi_init();???? /*设置gpio、使能位，初始化（设置设备时钟、读写速度、中断使能、检测设备类型等）*/

?

???? if (INF_REG3_REG == 1) {

??????????? puts("OneNAND: ");

??????????? onenand_init();

??????????? setenv("bootcmd","onenand read c0008000 40000 3c0000;bootm c0008000");

???? } else {

??????????? puts("NAND:??? ");

??????????? nand_init();???? /*填充oob_config结构，并打印flash容量*/

??????????? /*打印指令*/

??????????? if (INF_REG3_REG == 0 || INF_REG3_REG == 7)

?????????????????? setenv("bootcmd","movi read kernel c0008000;movi read rootfs c0800000;bootm c0008000");

??????????? else

?????????????????? setenv("bootcmd","nand read c0008000 40000 3c0000;bootm c0008000");????

???? }

?????? 该部分内容，首先初始化SD/MMC，然后对nand flash进行初始化，

8.?????? 若定义数据flash CONFIG_HAS_DATAFLASH，对其进行初始化：

该设备暂不涉及，暂不追究；

9.?????? env_relocate ();未知功能：

10.?? 设置MAC地址与网卡：

对网络知识欠缺，此部分内容跳过；

11.?? 设备初始化：

devices_init ();?????? /* get the devices list going. */

I2C、lcd、video、keyboard、logbuff、system、serial devices、usbtty、netconsole

12.?? 不解功能（line431-442）：

#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

13.?? 使能中断：

enable_interrupts ();

该函数调用汇编指令：

mrs %0,cpsr

bic %0,%0,#0x80

msr cpsr_c,%0

14.?? 网络部分设置内容（line448-466）：忽略

15.?? boot命令相关，不解（line468-476）

16.?? void main_loop(void)

命令循环主函数，根据相应命令，执行对应操作；

Note：friendlyARM公司在启动过程中加入了Menu函数和对应数字动作处理功能；