============================================================對於uboot兩階段的小結,很重要!!!==================================
第一階段:
在腳本uboot.lds中 ENTRY(_start) _start的地址一般是TEXT_BASE
設置異常向量表
進入svc管理模式 arm狀態
關看門狗 關中斷 時鐘初始化
cpu初始化(關mmu 關數據和指令緩存 cpu速率)和內存初始化 在函數cpu_init_crit中完成
重定位
設置棧
清bss斷
跳入到start_armboot函數
第二階段 就進入到lib_arm/board.c 中的start_kernel函數
分配gd 指針指向的空間和gd->bd 指針指向的空間
執行init_sequence 函數序列,其實主要目的是初始化並填充gd和gd->bd結構體
分配堆空間 mem_malloc_init ,這樣纔可以初始化環境變量,因爲環境變量是要從nand拷貝到內存中的堆空間裏
nand初始化 nand_init,因爲現在普及採用nand,若是用nor的話,在之前已經初始化了 flash_init 函數
環境變量初始化 env_reloacate 有四個很重要的環境變量參數:bootdelay(啓動延時),bootcmd(啓動命令),menucmd(菜單),bootargs(啓動參數,也即最原始的命令行參數)
串口設置的5個函數,這樣就能看到串口打印數據
混雜設備 misc_init_r函數
進入循環執行 main_loop函數,處理啓動命令或者用戶輸入的命令 該函數是在common/main.c 中
第一種情況是 在bootdelay內不按空格鍵:s=getenv ("bootcmd");run_command (s, 0); 直接啓動內核了
第二種輕狂就是 在bootdelay內按下空格鍵進入menu菜單裏: s = getenv("menucmd");run_command (s, 0);
然後進入命令循環獲取用戶從串口裏打印的字符 len = readline (CFG_PROMPT);run_command (lastcommand, flag);
之後在run_command裏if ((cmdtp = find_cmd(argv[0])) == NULL)--->if ((cmdtp->cmd) (cmdtp, flag, argc, argv) != 0)即根據
命令的名字 找到該命令表結構體,調用它的cmd參數 最終還是回到do_xxx run_command就是來解析命令的
run_command分別解析nand命令和bootm命令,nand命令負責把linux內核讀到內存中,bootm負責去啓動內核鏡像,調用do_bootm----->do_bootm_linux,啓動內核
/**************************** 開始第二階段分析 **************************************/
開始第二階段
第二階段是在lib_arm/board.c bootm.c兩個文件
start_armboot 是 U-Boot執行的第一個C語言函數,完成系統初始化工作,進入主循環,處理用戶輸入的命令。
看board.c 文件
#include <common.h>
#include <command.h>
#include <malloc.h>
#include <devices.h>
#include <version.h>
#include <net.h>
#include <serial.h>
#include <nand.h>
#include <onenand_uboot.h>
#ifdef CONFIG_DRIVER_SMC91111
#include "../drivers/net/smc91111.h"
#endif
#ifdef CONFIG_DRIVER_LAN91C96
#include "../drivers/net/lan91c96.h"
#endif
DECLARE_GLOBAL_DATA_PTR;
ulong monitor_flash_len;
#ifdef CONFIG_HAS_DATAFLASH
extern int AT91F_DataflashInit(void);
extern void dataflash_print_info(void);
#endif
#ifndef CONFIG_IDENT_STRING
#define CONFIG_IDENT_STRING ""
#endif
const char version_string[] =
U_BOOT_VERSION" (" __DATE__ " - " __TIME__ ")"CONFIG_IDENT_STRING;
#ifdef CONFIG_DRIVER_CS8900
extern void cs8900_get_enetaddr (uchar * addr);
#endif
#ifdef CONFIG_DRIVER_RTL8019
extern void rtl8019_get_enetaddr (uchar * addr);
#endif
#if defined(CONFIG_HARD_I2C) || \
defined(CONFIG_SOFT_I2C)
#include <i2c.h>
#endif
/*
* Begin and End of memory area for malloc(), and current "brk"
*/
static ulong mem_malloc_start = 0;
static ulong mem_malloc_end = 0;
static ulong mem_malloc_brk = 0;
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, 0,
mem_malloc_end - mem_malloc_start);
}
void *sbrk (ptrdiff_t increment)
{
ulong old = mem_malloc_brk;
ulong new = old + increment;
if ((new < mem_malloc_start) || (new > mem_malloc_end)) {
return (NULL);
}
mem_malloc_brk = new;
return ((void *) old);
}
/************************************************************************
* Coloured LED functionality
************************************************************************
* May be supplied by boards if desired
*/
void inline __coloured_LED_init (void) {}
void inline coloured_LED_init (void) __attribute__((weak, alias("__coloured_LED_init")));
void inline __red_LED_on (void) {}
void inline red_LED_on (void) __attribute__((weak, alias("__red_LED_on")));
void inline __red_LED_off(void) {}
void inline red_LED_off(void) __attribute__((weak, alias("__red_LED_off")));
void inline __green_LED_on(void) {}
void inline green_LED_on(void) __attribute__((weak, alias("__green_LED_on")));
void inline __green_LED_off(void) {}
void inline green_LED_off(void)__attribute__((weak, alias("__green_LED_off")));
void inline __yellow_LED_on(void) {}
void inline yellow_LED_on(void)__attribute__((weak, alias("__yellow_LED_on")));
void inline __yellow_LED_off(void) {}
void inline yellow_LED_off(void)__attribute__((weak, alias("__yellow_LED_off")));
/************************************************************************
* Init Utilities *
************************************************************************
* Some of this code should be moved into the core functions,
* or dropped completely,
* but let's get it working (again) first...
*/
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);
}
static int display_banner (void)
{
printf ("\n\n%s\n\n", version_string);
debug ("U-Boot code: %08lX -> %08lX BSS: -> %08lX\n",
_armboot_start, _bss_start, _bss_end);
#ifdef CONFIG_MODEM_SUPPORT
debug ("Modem Support enabled\n");
#endif
#ifdef CONFIG_USE_IRQ
debug ("IRQ Stack: %08lx\n", IRQ_STACK_START);
debug ("FIQ Stack: %08lx\n", FIQ_STACK_START);
#endif
return (0);
}
/*
* WARNING: this code looks "cleaner" than the PowerPC version, but
* has the disadvantage that you either get nothing, or everything.
* On PowerPC, you might see "DRAM: " before the system hangs - which
* gives a simple yet clear indication which part of the
* initialization if failing.
*/
static int display_dram_config (void) //打印顯示ram的配置信息
{
int i;
#ifdef DEBUG
puts ("RAM Configuration:\n");
for(i=0; i<CONFIG_NR_DRAM_BANKS; i++) {
printf ("Bank #%d: %08lx ", i, gd->bd->bi_dram[i].start);
print_size (gd->bd->bi_dram[i].size, "\n");
}
#else
ulong size = 0;
for (i=0; i<CONFIG_NR_DRAM_BANKS; i++) {
size += gd->bd->bi_dram[i].size;
}
puts("DRAM: ");
print_size(size, "\n");
#endif
return (0);
}
#ifndef CFG_NO_FLASH
static void display_flash_config (ulong size)
{
puts ("Flash: ");
print_size (size, "\n");
}
#endif /* CFG_NO_FLASH */
#if defined(CONFIG_HARD_I2C) || defined(CONFIG_SOFT_I2C)
static int init_func_i2c (void)
{
puts ("I2C: ");
i2c_init (CFG_I2C_SPEED, CFG_I2C_SLAVE);
puts ("ready\n");
return (0);
}
#endif
/*
* Breathe some life into the board...
*
* Initialize a serial port as console, and carry out some hardware
* tests.
*
* The first part of initialization is running from Flash memory;
* its main purpose is to initialize the RAM so that we
* can relocate the monitor code to RAM.
*/
/*
* All attempts to come up with a "common" initialization sequence
* that works for all boards and architectures failed: some of the
* requirements are just _too_ different. To get rid of the resulting
* mess of board dependent #ifdef'ed code we now make the whole
* initialization sequence configurable to the user.
*
* The requirements for any new initalization function is simple: it
* receives a pointer to the "global data" structure as it's only
* argument, and returns an integer return code, where 0 means
* "continue" and != 0 means "fatal error, hang the system".
*/
typedef int (init_fnc_t) (void);
int print_cpuinfo (void); /* test-only */
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 */ 打印uboot相關信息
#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 */
//配置可用的ram,非常重要,在這裏開始進行配置DRAM信息,用到結構體bd->bi_dram[BANK_NR].start
bd->bi_dram[BANK_NR].size
display_dram_config, //打印顯示ram的配置信息
NULL,
};
init_fnc_t *init_sequence[ ] = {
cpu_init, /* 基本的處理器相關配置 -- cpu/arm920t/cpu.c */
board_init, /* 基本的板級相關配置 -- board/smdk2410/smdk2410.c */
interrupt_init, /* 初始化中斷處理 -- cpu/arm920t/s3c24x0/interrupt.c */
env_init, /* 初始化環境變量 -- common/cmd_flash.c */
init_baudrate, /* 初始化波特率設置 -- lib_arm/board.c */
serial_init, /* 串口通訊設置 -- cpu/arm920t/s3c24x0/serial.c */
console_init_f, /* 控制檯初始化階段1 -- common/console.c */
display_banner, /* 打印u-boot信息 -- lib_arm/board.c */
dram_init, /* 配置可用的RAM -- board/smdk2410/smdk2410.c */
display_dram_config, /* 顯示RAM的配置大小 -- lib_arm/board.c */
NULL,
};
void start_armboot (void) //start_armboot函數 非常重要,c function第一個函數!!!
{
init_fnc_t **init_fnc_ptr;
char *s;
#if !defined(CFG_NO_FLASH) || defined (CONFIG_VFD) || defined(CONFIG_LCD)
ulong size;
#endif
#if defined(CONFIG_VFD) || defined(CONFIG_LCD)
unsigned long addr;
#endif
//在重定位之後,即uboot的代碼從flash拷到sdram 此時連接腳本里的_start 等於TEXT_BASE
/* Pointer is writable since we allocated a register for it */
// 給全局變量gd分配空間大小且指定gd的位置 這裏gd是一個結構體,在uboot內存分佈中
是CFG_GBL_DATA_SIZE一共128字節
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指針所指向的空間清零
gd->bd = (bd_t*)((char*)gd - sizeof(bd_t)); //給gd中的bd指針分配空間大小
memset (gd->bd, 0, sizeof (bd_t)); //gd->bd 所指向的空間清零
gd->flags |= GD_FLG_RELOC;
monitor_flash_len = _bss_start - _armboot_start; //uboot鏡像文件的大小
for (init_fnc_ptr = init_sequence; *init_fnc_ptr; ++init_fnc_ptr) {
//執行初始化序列函數 這裏是調用了一系列的c函數指針,進行初始化。
比如cpu_init初始化完成各個gpio管腳初始化,board_init完成arch_number設置和boot_params約定存放地址,還有串口初始化等。
if ((*init_fnc_ptr)() != 0) {
hang ();
}
}
board/smdk2410/flash.c配置flash
#ifndef CFG_NO_FLASH 識別出來是哪一種flash nor還是nand 如果定義了CFG_NO_FLASH這個宏,說明是nand 否則是nor
/* configure available FLASH banks */
size = flash_init (); //nor型flash的初始化
display_flash_config (size);
#endif /* CFG_NO_FLASH */
定義顯示類型 分vfd和lcd兩種。vfd一般不用,我們用lcd的
在這裏定義了幀緩衝,也就顯存的的地址和大小
-----------------------------------------------------------------------------------------------------------
#ifdef CONFIG_VFD
# ifndef PAGE_SIZE
# define PAGE_SIZE 4096 //定義頁大小4k
# 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 //在內存中配置一塊幀緩衝區
/* board init may have inited fb_base */
if (!gd->fb_base) {
# 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); 按頁對其方式保留顯存
size = lcd_setmem (addr); // 分配幀緩衝區的大小
gd->fb_base = addr; // 幀緩衝區的物理起始地址
}
#endif /* CONFIG_LCD */
--------------------------------------------------------------------------------------------------------------------
/* armboot_start is defined in the board-specific linker script */
mem_malloc_init (_armboot_start - CFG_MALLOC_LEN); //分配堆空間大小 這樣纔可以初始化環境變量
//初始化nand flash,這是在nand flash啓動的s3c2410移植u-boot的關鍵,根據flash時序編寫函數即可
//在include/configs/smdk2410.h中的command definition中增加CONFIG_COMMANDS和CFG_CMD_NAND命令
//nand型flash的初始化
#if defined(CONFIG_CMD_NAND)
puts ("NAND: "); 打印標誌: NAND: 64MB
nand_init(); /* go init the NAND */ //board/smdk2410/smdk2410.c,獲取nand的基地址和 大小信息
#endif
#if defined(CONFIG_CMD_ONENAND) 三星的一種特別的flash onenand,類似於nand
onenand_init();
#endif
#ifdef CONFIG_HAS_DATAFLASH
AT91F_DataflashInit();
dataflash_print_info();
#endif
/* initialize environment */
env_relocate ();
//環境變量的初始化 該函數是在commen/env_commen.c中定義的,在該文件中還定義了一個默認下的環境變量
default_enviornment[] 第一次啓動時,nand 默認裏面是沒有環境變量的,則根據板文件的宏選用默認的環境變量。
可以進行修改通過saveenv進行保存到nand裏。
//env_relocate將環境變量從存儲設備中讀取到全局變量env_t env_ptr的data裏面,由於該函數從以上堆空間
//中分配空間,所以我們的環境變量都放在了堆空間裏面了
env_relocate ----> env_ptr = (env_t *)malloc (CONFIG_ENV_SIZE); gd->env_addr = (ulong)&(env_ptr->data);此處是告訴
環境變量存放在內存中的地址自此, 環境變量已經存放在內存gd->env_addr處,這樣就可以獲取環境變量或者
修改環境變量保存到nand中去了
#ifdef CONFIG_VFD //framebuffer初始化
/* must do this after the framebuffer is allocated */
drv_vfd_init(); //video的初始化
#endif /* CONFIG_VFD */
#ifdef CONFIG_SERIAL_MULTI //多串口
serial_initialize();
#endif
//從環境變量中獲取IP地址 以太網接口MAC地址 主要是初始化 gd->bd->bi_ip_addr和gd->bd->bi_enetaddr[]
-----------------------------------------------------------------
/* IP Address */
gd->bd->bi_ip_addr = getenv_IPaddr ("ipaddr"); 通過讀取環境變量的ip地址
/* 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 如果要是有兩塊以太網卡
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. */ 註冊設備鏈表,其實也就只註冊了一個串口設備
#ifdef CONFIG_CMC_PU2
load_sernum_ethaddr ();
#endif /* CONFIG_CMC_PU2 */
jumptable_init ();
console_init_r ();/* fully init console as a device */
//控制檯設備的初始化階段2 到這裏終於可以從控制檯上看到數據打印出來了
------------------------------------------------------------------------------------------------------
注意:從串口寄存器的設置到最終在終端上打印信息,是有以下函數組成的。
在init_sequense裏的三個函數和
init_baudrate, 設置 gd->bd->bi_baudrate
serial_init, 直接調用serial_setbrg函數初始化UART寄存器:8個數據位,一個開始位,一個停止位,無校驗位。。。
console_init_f, 控制檯前期初始化 設置gd->have_console=1
devices_init, 調用drv_system_init 註冊串口設備
console_init_r 控制檯後期初始化,將串口設備指向控制檯標準輸入設備,標準輸出設備,標準錯誤設備
In: serial
Out: serial
Err: serial
打印這三行信息,表明串口作爲標準輸入設備,標準輸出設備,標準錯誤輸出設備,這樣就能打印信息了
默認情況下,鍵盤和鼠標默認爲標準輸入設備,顯示器默認爲標準輸出設備和標準錯誤輸出設備,printf爲標準格式輸出
scanf爲標準格式輸入。標準輸入,標準輸出設備的重定向即將串口設備作爲標準輸入設備,將串口做爲標準輸出設備和
標準錯誤輸出設備
static void drv_system_init (void)
static void drv_system_init (void)
{
device_t dev; //定義一個設備結構體
memset (&dev, 0, sizeof (dev));//爲剛剛定義的結構體分配內存
strcpy (dev.name, "serial"); //名稱
dev.flags = DEV_FLAGS_OUTPUT | DEV_FLAGS_INPUT | DEV_FLAGS_SYSTEM; 設備的類型
#ifdef CONFIG_SERIAL_SOFTWARE_FIFO
dev.putc = serial_buffered_putc;
dev.puts = serial_buffered_puts;
dev.getc = serial_buffered_getc;
dev.tstc = serial_buffered_tstc;
#else
dev.putc = serial_putc;
dev.puts = serial_puts;
dev.getc = serial_getc;
dev.tstc = serial_tstc;
#endif
填充該設備結構體並註冊
device_register (&dev);//註冊函數 將該串口設備註冊到devlist
#ifdef CFG_DEVICE_NULLDEV
memset (&dev, 0, sizeof (dev));
strcpy (dev.name, "nulldev");
dev.flags = DEV_FLAGS_OUTPUT | DEV_FLAGS_INPUT | DEV_FLAGS_SYSTEM;
dev.putc = nulldev_putc;
dev.puts = nulldev_puts;
dev.getc = nulldev_input;
dev.tstc = nulldev_input;
device_register (&dev);
#endif
}
console_init_r 函數
2 int console_init_r (void)
3 {
4 device_t *inputdev = NULL, *outputdev = NULL; 定義兩個設備
5 int i, items = ListNumItems (devlist); // 取得設備鏈中的設備數 因爲只註冊了一個設備,即items=1
6 /* Scan devices looking for input and output devices */
7 for (i = 1;
8 (i <= items) && ((inputdev == NULL) || (outputdev == NULL));
9 i++
10 ) {
11 device_t *dev = ListGetPtrToItem (devlist, i); 從devlist中獲取該串口設備
12 if ((dev->flags & DEV_FLAGS_INPUT) && (inputdev == NULL)) { 執行
13 inputdev = dev; 即輸入設備爲該串口設備
14 }
15 if ((dev->flags & DEV_FLAGS_OUTPUT) && (outputdev == NULL)) { 執行
16 outputdev = dev; 即輸出設備也爲該串口設備
17 }
18 }
// 7~18行,在設備鏈中按註冊的順序查找輸入輸出設備,在設備註冊時 dev.flags表示此設備的類型。
// 比如這裏drv_system_init,此設備是第一個註冊的設備,且其dev.flags爲
// DEV_FLAGS_OUTPUT | DEV_FLAGS_INPUT | DEV_FLAGS_SYSTEM 所以上面18行過後,輸入輸出設備都指定爲
// drv_system_init裏註冊的設備了
console_setfile 是最關鍵的地方,在這裏纔是真正的給我們的標準輸入設備,標準輸出設備,標準錯誤輸出設備填充結構
19 /* Initializes output console first */
20 if (outputdev != NULL) {
通過console_setfile()函數可以看出,控制檯有一個包含 3 個 device_t 元素的數組stdio_devices,分別對應
stdin,stdout,stderr。
通過 stdio_devices[file] = dev 就可以將dev設成設置控制檯的某個設備。這樣就實現了控制檯任意選擇設備的功能。
這和 linux 的設計思想有點類似。
21 console_setfile (stdout, outputdev); 即stdio_devices[stdout]=outputdev
22 console_setfile (stderr, outputdev); 即stdio_devices[stderr]=outputdev
23 }
24 /* Initializes input console */
25 if (inputdev != NULL) {
26 console_setfile (stdin, inputdev); 即stdio_devices[stdin]=inputdev
27 } 將控制檯的標準輸入設備,標準輸出設備,標註錯誤輸出設備均設爲串口設備
21~27行, console_setfile做如下幾件事:
1. 如果初始化該設備時註冊了device_t.start,即啓動設備的函數,則運行該函數,開啓該設備
2. 將設備的指針存入stdio_devices[file],這應該是標準輸入標準輸出、標準出錯。
#define stdin 0
#define stdout 1
#define stderr 2
22行將標準出錯定爲輸出設備,這樣有錯誤信息就會通過輸出設備打印出來了
28 gd->flags |= GD_FLG_DEVINIT; /* device initialization completed */
29 /* Print information */
30 puts ("In: ");
31 if (stdio_devices[stdin] == NULL) {
32 puts ("No input devices available!\n");
33 } else {
34 printf ("%s\n", stdio_devices[stdin]->name);
35 }
36 puts ("Out: ");
37 if (stdio_devices[stdout] == NULL) {
38 puts ("No output devices available!\n");
39 } else {
40 printf ("%s\n", stdio_devices[stdout]->name);
41 }
42 puts ("Err: ");
43 if (stdio_devices[stderr] == NULL) {
44 puts ("No error devices available!\n");
45 } else {
46 printf ("%s\n", stdio_devices[stderr]->name);
47 }
30~47行,將信息打印出來,這裏打印出出的信息就爲
In: serial
Out: serial
Err: serial
48 /* Setting environment variables */
49 for (i = 0; i < 3; i++) {
50 setenv (stdio_names[i], stdio_devices[i]->name);// 即stdin=serial
51 } stdout = serial
49~51行 將信息寫到環境變量中去
char *stdio_names[MAX_FILES] = { "stdin", "stdout", "stderr" };
這樣環境變量裏 stdin stdout stderr 都爲serial
52 return (0);
53 }
---------------------------------------------------------------------------------------------------------------------------------------
#if defined(CONFIG_MISC_INIT_R)
/* miscellaneous platform dependent initialisations */
misc_init_r (); //混雜設備的初始化 很重要
#endif
/* enable exceptions */
enable_interrupts (); //使能中斷 即打開cpsr_c的第7位 即外中斷,該第7位值爲0,表示使能外中斷
/* Perform network card initialisation if necessary */
配置幾種類型的網卡
#ifdef CONFIG_DRIVER_TI_EMAC
extern void davinci_eth_set_mac_addr (const u_int8_t *addr);
if (getenv ("ethaddr")) {
davinci_eth_set_mac_addr(gd->bd->bi_enetaddr);
}
#endif
#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 defined(CONFIG_CMD_NET)
if ((s = getenv ("bootfile")) != NULL) {
copy_filename (BootFile, s, sizeof (BootFile));
}
#endif
#ifdef BOARD_LATE_INIT
board_late_init ();
#endif
#if defined(CONFIG_CMD_NET)
#if defined(CONFIG_NET_MULTI)
puts ("Net: ");
#endif
eth_initialize(gd->bd);
#if defined(CONFIG_RESET_PHY_R)
debug ("Reset Ethernet PHY\n");
reset_phy();
#endif
#endif
/*****************************************非常重要**************************************/
/* main_loop() can return to retry autoboot, if so just run it again. */
// for(;;)與while(1) 是一樣的,for(;;)編譯成彙編後是無條件轉移,while(1)是要0和1進行一下比較的,
所以從這個方向上看for(;;)是要比while(1)快的因爲少了一個比較指令,但現在的編譯器都是有一定的
優化能力的,像while(1)這種會優化成和for(;;)一樣的彙編代碼
for (;;) {
main_loop ();
//進入主循環 主循環函數處理執行用戶命令 main_loop 是在common/main.c 中定義和實現的
}
/* NOTREACHED - no way out of command loop except booting */
}
void hang (void)
{
puts ("### ERROR ### Please RESET the board ###\n");
for (;;);
}
#ifdef CONFIG_MODEM_SUPPORT
static inline void mdm_readline(char *buf, int bufsiz);
/* 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[];
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 */
以下是main_loop函數的分析 該文件在common/main.c中
void main_loop (void)
{
#ifndef CFG_HUSH_PARSER // CFG_HUSH_PARSER沒有定義,所以執行
static char lastcommand[CFG_CBSIZE] = { 0, }; CFG_CBSIZE爲256 用於記錄console buffer size
int len;
int rc = 1;
int flag;
#endif
#if defined(CONFIG_BOOTDELAY) && (CONFIG_BOOTDELAY >= 0)
// 執行 定義指針s和int型bootdelay。用於uboot判斷無任何按鍵按下,就執行CONFIG_BOOTCOMMAND宏所對應的命令,這個命令通常用於加載啓動操作系統;
char *s;
int bootdelay;
#endif
#ifdef CONFIG_PREBOOT 沒定義,不執行
char *p;
#endif
#ifdef CONFIG_BOOTCOUNT_LIMIT 沒定義 不執行
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) 沒定義 但是我們可以定義,讓顯示開機log
ulong bmp = 0; /* default bitmap */
extern int trab_vfd (ulong bitmap);
#ifdef CONFIG_MODEM_SUPPORT 沒定義
if (do_mdm_init)
bmp = 1; /* alternate bitmap */
#endif
trab_vfd (bmp);
#endif /* CONFIG_VFD && VFD_TEST_LOGO */
#ifdef CONFIG_BOOTCOUNT_LIMIT 沒定義 不執行
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 暫時不支持通話 沒定義 不執行
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 沒定義 不執行
{
extern char version_string[];
setenv ("ver", version_string); /* set version variable */ 設置環境變量ver=“”
}
#endif /* CONFIG_VERSION_VARIABLE */
#ifdef CFG_HUSH_PARSER 沒定義 不執行
u_boot_hush_start ();
#endif
#ifdef CONFIG_AUTO_COMPLETE 該宏非常好用,可以讓我們自動補齊命令
install_auto_complete();
#endif
#ifdef CONFIG_PREBOOT 沒定義 不執行
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)
s = getenv ("bootdelay"); //獲取環境變量bootdelay的值 即將環境變量bootdelay等號後面的值的地址保存在s ,即s保存字符串的地址,比如是5,即5此時是字符串
bootdelay = s ? (int)simple_strtol(s, NULL, 10) : CONFIG_BOOTDELAY; //如果環境變量中沒有bootdelay參數,則就用默認的CONFIG_BOOTDELAY來當作倒數計時
bootdelay保存該環境變量的值
debug ("### main_loop entered: bootdelay=%d\n\n", bootdelay);
# ifdef CONFIG_BOOT_RETRY_TIME 不執行
init_cmd_timeout ();
# endif /* CONFIG_BOOT_RETRY_TIME */
#ifdef CONFIG_POST
if (gd->flags & GD_FLG_POSTFAIL) {
s = getenv("failbootcmd");
}
else
#endif /* CONFIG_POST */
#ifdef CONFIG_BOOTCOUNT_LIMIT 不執行
if (bootlimit && (bootcount > bootlimit)) {
printf ("Warning: Bootlimit (%u) exceeded. Using altbootcmd.\n",
(unsigned)bootlimit);
s = getenv ("altbootcmd");
}
else
#endif /* CONFIG_BOOTCOUNT_LIMIT */
*******************************************************************************************************************************************
以下是兩種情況
第一種情況是 在bootdelay內不按空格鍵: s=getenv ("bootcmd");run_command (s, 0); 直接啓動內核了
第二種情況就是 在bootdelay內按下空格鍵: s = getenv("menucmd");run_command (s, 0); 進入命令循環
len = readline (CFG_PROMPT);run_command (lastcommand, flag); 之後在run_command裏
if ((cmdtp = find_cmd(argv[0])) == NULL)--->if ((cmdtp->cmd) (cmdtp, flag, argc, argv) != 0)即根據命令的名字
找到該命令表結構體,調用它的cmd參數 最終還是回到do_xxx
比如 run_command("bootm")---->根據“bootm”名字會在命令表裏去找到相應的命令表,最終用該命令表的
cmd參數即do_bootm去處理宏U_BOOT_CMD定義了一個段屬性爲.u_boot_cmd的命令表結構體 struct cmd_tbl_t
s = getenv ("bootcmd"); //啓動命令 非常重要 bootcmd = nand read 目的地址 源地址; bootm 目的地址
debug ("### main_loop: bootcmd=\"%s\"\n", s ? s : "<UNDEFINED>");
if (bootdelay >= 0 && s && !abortboot (bootdelay)) { //如果倒數計時之內沒有按空格鍵 則直接
run_command (s, 0) 直接啓動內核了
# ifdef CONFIG_AUTOBOOT_KEYED 不執行
int prev = disable_ctrlc(1); /* disable Control C checking */
# endif
# ifndef CFG_HUSH_PARSER
run_command (s, 0); //直接啓動內核了
# 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"); //否則如果在倒數計時之內按下了空格鍵,就會跑到這裏來
if (s) {
# ifndef CFG_HUSH_PARSER
run_command (s, 0); //就會進入到菜單裏面 當然你需要自己去實現這個菜單
# 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
/*
* Main Loop for Monitor Command Processing //進入循環 處理用戶輸入的命令
*/
#ifdef CFG_HUSH_PARSER
parse_file_outer();
/* This point is never reached */
for (;;);
#else //執行else分支 在這裏進入循環來處理各種用戶輸入的命令
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); //讀取串口裏用戶輸入的命令 一回車這些輸入的字符串就被考入到console_buffer裏 len表示獲取的字符串長度
flag = 0; /* assume no special flags for now */
if (len > 0)
strcpy (lastcommand, console_buffer); //將用戶輸入的命令字符串拷貝到lastcommand裏
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); //解析和處理用戶輸入的命令
if (rc <= 0) {
/* invalid command or not repeatable, forget it */
lastcommand[0] = 0;
}
}
#endif /*CFG_HUSH_PARSER*/
}
----------------------------------------------------------------------------------------------------
----------------------------------------------------------------------------------------------------
----------------------------------------------------------------------------------------------------
main_loop又臭又長,去掉宏註釋掉的部分就只剩下一點點了。如下:
void main_loop (void)
{
#ifndef CONFIG_SYS_HUSH_PARSER
static char lastcommand[CONFIG_SYS_CBSIZE] = { 0, };
int len;
int rc = 1;
int flag;
#endif
#if defined(CONFIG_BOOTDELAY) && (CONFIG_BOOTDELAY >= 0)
char *s;
int bootdelay;
#endif
#ifdef CONFIG_AUTO_COMPLETE
install_auto_complete(); //安裝自動補全的函數,分析如下 。
#endif
#if defined(CONFIG_BOOTDELAY) && (CONFIG_BOOTDELAY >= 0)
s = getenv ("bootdelay");
bootdelay = s ? (int)simple_strtol(s, NULL, 10) : CONFIG_BOOTDELAY;
debug ("### main_loop entered: bootdelay=%d/n/n", bootdelay);
s = getenv ("bootcmd"); //獲取引導命令。分析見下面。
debug ("### main_loop: bootcmd=/"%s/"/n", s ? s : "<UNDEFINED>");
if (bootdelay >= 0 && s && !abortboot (bootdelay)) { //如果延時大於等於零,並且沒有在延時過程中接收到按鍵,則引導內核。abortboot函數的分析見下面。
/* 重點1 */
run_command (s, 0); //運行引導內核的命令。這個命令是在配置頭文件中定義的。run_command的分析在下面。
}
#endif /* CONFIG_BOOTDELAY */
for (;;) { 否則就進入uboot命令行執行各個uboot命令了
len = readline (CONFIG_SYS_PROMPT); //CONFIG_SYS_PROMPT的意思是回顯字符,一般是“>”。這是由配置頭文件定義的 readline讀入用戶輸入的字符串,存放在console_buffer
flag = 0; /* assume no special flags for now */
if (len > 0)
strcpy (lastcommand, console_buffer); //保存輸入的數據。
else if (len == 0)
flag |= CMD_FLAG_REPEAT;//如果輸入數據爲零,則重複執行上次的命令,如果上次輸入的是一個命令的話
if (len == -1)
puts ("<INTERRUPT>/n");
else
rc = run_command (lastcommand, flag); //執行命令 ,重點2。
if (rc <= 0) {//執行失敗,則清空記錄
/* invalid command or not repeatable, forget it */
lastcommand[0] = 0;
}
}
}
2。自動補全
common/common.c
int var_complete(int argc, char *argv[], char last_char, int maxv, char *cmdv[])
{
static char tmp_buf[512];
int space;
space = last_char == '/0' || last_char == ' ' || last_char == '/t';
if (space && argc == 1)
return env_complete("", maxv, cmdv, sizeof(tmp_buf), tmp_buf);
if (!space && argc == 2)
return env_complete(argv[1], maxv, cmdv, sizeof(tmp_buf), tmp_buf);
return 0;
}
static void install_auto_complete_handler(const char *cmd,
int (*complete)(int argc, char *argv[], char last_char, int maxv, char *cmdv[]))
{
cmd_tbl_t *cmdtp;
cmdtp = find_cmd(cmd);
if (cmdtp == NULL)
return;
cmdtp->complete = complete; //命令結構體的complete指針指向傳入的函數。
}
void install_auto_complete(void)
{
#if defined(CONFIG_CMD_EDITENV)
install_auto_complete_handler("editenv", var_complete);
#endif
install_auto_complete_handler("printenv", var_complete);
install_auto_complete_handler("setenv", var_complete);
#if defined(CONFIG_CMD_RUN)
install_auto_complete_handler("run", var_complete);
#endif
}
可以看到將editenv、printenv、setenv和run的自動補全函數安裝爲 var_complete。
var_complete的功能是根據給出的前綴字符串,找出所有前綴相同的命令。
每個命令在內存中用一個cmd_tbl_t 表示。
include/command.h
struct cmd_tbl_s {
char *name; /* 命令名,輸入的就是它 */
int maxargs; /* 最大參數個數 */
int repeatable; /* 允許自動重發,也就是在按下空格鍵之後執行最後一條命令。 */
int (*cmd)(struct cmd_tbl_s *, int, int, char *[]); /* 實現命令的參數 */
char *usage; /* 短的提示信息 */
#ifdef CONFIG_SYS_LONGHELP
char *help; /* 詳細的幫助信息。 */
#endif
#ifdef CONFIG_AUTO_COMPLETE
/* do auto completion on the arguments */
int (*complete)(int argc, char *argv[], char last_char, int maxv, char *cmdv[]);
#endif
};
typedef struct cmd_tbl_s cmd_tbl_t;
extern cmd_tbl_t __u_boot_cmd_start;
extern cmd_tbl_t __u_boot_cmd_end;
#define U_BOOT_CMD(name,maxargs,rep,cmd,usage,help) / U_BOOT_CMD宏定義了一個cmd_tbl_t結構的uboot命令,用find_cmd(argv[0])) 參數是命令的名字,根據名字找到該命令結構cmd_tbl_t
cmd_tbl_t __u_boot_cmd_##name Struct_Section = {#name, maxargs, rep, cmd, usage, help}
#define U_BOOT_CMD_MKENT(name,maxargs,rep,cmd,usage,help) /
{#name, maxargs, rep, cmd, usage, help}
uboot中的命令使用U_BOOT_CMD這個宏聲明來註冊進系統,鏈接腳本會把所有的cmd_tbl_t結構體放在相鄰的地方。
鏈接腳本中的一些內容如下:
. = .;
__u_boot_cmd_start = .;
.u_boot_cmd : { *(.u_boot_cmd) }
__u_boot_cmd_end = .;
可見,__u_boot_cmd_start 和__u_boot_cmd_end 分別對應命令結構體在內存中開始和結束的地址。
3。abortboot 函數的分析
abortboot是uboot在引導期間的延時函數。期間可以按鍵進入uboot的命令行。
common/main.c
static __inline__ int abortboot(int bootdelay) 該函數 即在延時時間內,若掃描有鍵按下即返回1,若無鍵按下 則返回0
{
int abort = 0;
printf("Hit any key to stop autoboot: %2d ", bootdelay);
#if defined CONFIG_ZERO_BOOTDELAY_CHECK //如果定義了這個宏,即使定義延時爲0,也會檢查一次是否有按鍵按下。只要在這裏執行之前按鍵,還是能進入uboot的命令行。
if (bootdelay >= 0) {
if (tstc()) { /* we got a key press */ 測試是否有按鍵按下
(void) getc(); /* consume input */接收按鍵值
puts ("/b/b/b 0");
abort = 1; /* don't auto boot */修改標記,停止自動引導
}
}
#endif
while ((bootdelay > 0) && (!abort)) { //如果延時大於零並且停止標記沒有賦值則進入延時循環,直到延時完或者接收到了按 鍵
int i;
--bootdelay;
/* delay 100 * 10ms */ 每秒中測試按鍵100次,之後延時10ms。
for (i=0; !abort && i<100; ++i) {
if (tstc()) { /* we got a key press */
abort = 1; /* don't auto boot */*/修改標記,停止自動引導
bootdelay = 0; /* no more delay */延時歸零
(void) getc(); /* consume input */獲取按鍵
break;
}
udelay(10000);//延時10000us,也就是10ms
}
printf("/b/b/b%2d ", bootdelay);//打印當前剩餘時間
}
putc('/n');
return abort;//返回結果:1-停止引導,進入命令行; 0-引導內核。
}
可以看到uboot延時的單位是秒,如果想提高延時的精度,比如想進行10ms級的延時,將udelay(10000)改爲udelay(100)就可以了 。
run_command 重點
//////////////////////////////////////////////////////////////////////////////////////////////////////////
int run_command (const char *cmd, int flag)
{
cmd_tbl_t *cmdtp;
char cmdbuf[CONFIG_SYS_CBSIZE]; /* working copy of cmd */
char *token; /* start of token in cmdbuf */
char *sep; /* end of token (separator) in cmdbuf */
char finaltoken[CONFIG_SYS_CBSIZE];
char *str = cmdbuf;
char *argv[CONFIG_SYS_MAXARGS + 1]; /* NULL terminated */
int argc, inquotes;
int repeatable = 1;
int rc = 0;
clear_ctrlc(); /* forget any previous Control C */
if (!cmd || !*cmd) {
return -1; /* empty command */ 空命令
}
if (strlen(cmd) >= CONFIG_SYS_CBSIZE) { //命令太長
puts ("## Command too long!/n");
return -1;
}
strcpy (cmdbuf, cmd); //將命令拷貝到臨時命令緩衝cmdbuf
/* Process separators and check for invalid
* repeatable commands
*/
while (*str) { //str指向cmdbuf
/*
* Find separator, or string end
* Allow simple escape of ';' by writing "/;"
*/
for (inquotes = 0, sep = str; *sep; sep++) {
//尋找分割符或者命令尾部。相鄰的句子之間是用;隔開的。每次處理一句命令
if ((*sep=='/'') &&
(*(sep-1) != '//'))
inquotes=!inquotes;
if (!inquotes &&
(*sep == ';') && /* separator */
( sep != str) && /* past string start */
(*(sep-1) != '//')) /* and NOT escaped */
break;
}
/*
* Limit the token to data between separators
*/
token = str; //token指向命令的開頭
if (*sep) { //如果是分隔符的話,將分隔符替換爲空字符
str = sep + 1; /* start of command for next pass */str指向下一句的開頭
*sep = '/0';
}
else
str = sep; /* no more commands for next pass */如果沒有其它命令了,str指向命令尾部
/* find macros in this token and replace them */
process_macros (token, finaltoken);
//將token指向的命令中的宏替換掉,如把$(kernelsize)替換成內核的大小
/* Extract arguments */
if ((argc = parse_line (finaltoken, argv)) == 0) {
//將每一個參數用‘/0’隔開,argv中的每一個指針指向一個參數的起始地址。 返回值爲參數的個數
rc = -1; /* no command at all */
continue;
}
/* Look up command in command table */
if ((cmdtp = find_cmd(argv[0])) == NULL) {
//第一個參數就是要運行的命令,首先在命令表中找到它的命令結構體的指針
printf ("Unknown command '%s' - try 'help'/n", argv[0]);
rc = -1; /* give up after bad command */
continue;
}
/* found - check max args */
if (argc > cmdtp->maxargs) { //檢查參數個數是否過多
cmd_usage(cmdtp);
rc = -1;
continue;
}
/* OK - call function to do the command */
if ((cmdtp->cmd) (cmdtp, flag, argc, argv) != 0) { //調用命令執行函數。這是最重要的一步。
rc = -1;
}
repeatable &= cmdtp->repeatable;
//設置命令自動重複執行的標誌。也就是隻按下enter鍵是否可以執行最近執行的命令 .
/* Did the user stop this? */
if (had_ctrlc ())
//檢查是否有ctrl+c按鍵按下,如果有,結束當前命令。本函數並沒有從中斷接收字符,接收ctrl+c的是一些執行命令的函數。
return -1; /* if stopped then not repeatable */
}
return rc ? rc : repeatable;
}
---------------------------------------------------------------------------------------------------
其實 main_loop 函數就是處理兩個run_command 函數,一個是在開機延遲時間內若沒有按下任意鍵,則
直接啓動內核(bootcmd);一個是若按下了,則不會啓動內核,處理uboot命令
uboot最核心的東西就是命令,關於uboot命令的章節筆記本上都有,此處略。
現在來看uboot的最後一部分 啓動內核
啓動內核 s=getenv ("bootcmd");run_command (s, 0);
環境變量bootcmd = nand read 目的地址 源地址 大小; bootm 目的地址
只要是啓動內核,就一定要用到bootcmd,執行這兩條指令
nand read指令的實現是在cmd_nand.c文件中的do_nand函數中實現的,do_nand函數中有很多關於nand命令
比如 nand write,nand erase等等
***************************************************************************************************************
我們來看下關於nand相關的指令實現的函數 do_nand
int do_nand(cmd_tbl_t * cmdtp, int flag, int argc, char *argv[])
{
int i, dev, ret = 0;
ulong addr, off;
size_t size;
char *cmd, *s;
nand_info_t *nand;
#ifdef CFG_NAND_QUIET
int quiet = CFG_NAND_QUIET;
#else
int quiet = 0;
#endif
const char *quiet_str = getenv("quiet");
/* at least two arguments please */
if (argc < 2) //r如果參數的個數小於2個 退出,也即參數的個數至少是兩個 如nand read
goto usage;
if (quiet_str)
quiet = simple_strtoul(quiet_str, NULL, 0) != 0;
cmd = argv[1]; //獲取nand 後面的那一個命令
if (strcmp(cmd, "info") == 0) { //命令 nand info
putc('\n');
for (i = 0; i < CFG_MAX_NAND_DEVICE; i++) {
if (nand_info[i].name)
printf("Device %d: %s, sector size %u KiB\n",
i, nand_info[i].name,
nand_info[i].erasesize >> 10);
}
return 0;
}
if (strcmp(cmd, "device") == 0) { // 命令 nand device
if (argc < 3) {
if ((nand_curr_device < 0) ||
(nand_curr_device >= CFG_MAX_NAND_DEVICE))
puts("\nno devices available\n");
else
printf("\nDevice %d: %s\n", nand_curr_device,
nand_info[nand_curr_device].name);
return 0;
}
dev = (int)simple_strtoul(argv[2], NULL, 10);
if (dev < 0 || dev >= CFG_MAX_NAND_DEVICE || !nand_info[dev].name) {
puts("No such device\n");
return 1;
}
printf("Device %d: %s", dev, nand_info[dev].name);
puts("... is now current device\n");
nand_curr_device = dev;
#ifdef CFG_NAND_SELECT_DEVICE
/*
* Select the chip in the board/cpu specific driver
*/
board_nand_select_device(nand_info[dev].priv, dev);
#endif
return 0;
}
if (strcmp(cmd, "bad") != 0 && strcmp(cmd, "erase") != 0 &&
strncmp(cmd, "dump", 4) != 0 &&
strncmp(cmd, "read", 4) != 0 && strncmp(cmd, "write", 5) != 0 &&
strcmp(cmd, "scrub") != 0 && strcmp(cmd, "markbad") != 0 &&
strcmp(cmd, "biterr") != 0 &&
strcmp(cmd, "lock") != 0 && strcmp(cmd, "unlock") != 0 )
goto usage;
/* the following commands operate on the current device */
if (nand_curr_device < 0 || nand_curr_device >= CFG_MAX_NAND_DEVICE ||
!nand_info[nand_curr_device].name) {
puts("\nno devices available\n");
return 1;
}
nand = &nand_info[nand_curr_device];
if (strcmp(cmd, "bad") == 0) {
printf("\nDevice %d bad blocks:\n", nand_curr_device);
for (off = 0; off < nand->size; off += nand->erasesize)
if (nand_block_isbad(nand, off))
printf(" %08lx\n", off);
return 0;
}
/*
* Syntax is:
* 0 1 2 3 4
* nand erase [clean] [off size]
*/
if (strcmp(cmd, "erase") == 0 || strcmp(cmd, "scrub") == 0) {
nand_erase_options_t opts;
/* "clean" at index 2 means request to write cleanmarker */
int clean = argc > 2 && !strcmp("clean", argv[2]);
int o = clean ? 3 : 2;
int scrub = !strcmp(cmd, "scrub");
printf("\nNAND %s: ", scrub ? "scrub" : "erase");
/* skip first two or three arguments, look for offset and size */
if (arg_off_size(argc - o, argv + o, nand, &off, &size) != 0)
return 1;
memset(&opts, 0, sizeof(opts));
opts.offset = off;
opts.length = size;
opts.jffs2 = clean;
opts.quiet = quiet;
if (scrub) {
puts("Warning: "
"scrub option will erase all factory set "
"bad blocks!\n"
" "
"There is no reliable way to recover them.\n"
" "
"Use this command only for testing purposes "
"if you\n"
" "
"are sure of what you are doing!\n"
"\nReally scrub this NAND flash? <y/N>\n");
if (getc() == 'y' && getc() == '\r') {
opts.scrub = 1;
} else {
puts("scrub aborted\n");
return -1;
}
}
ret = nand_erase_opts(nand, &opts); //真正解析該命令的函數
printf("%s\n", ret ? "ERROR" : "OK");
return ret == 0 ? 0 : 1;
}
if (strncmp(cmd, "dump", 4) == 0) {
if (argc < 3)
goto usage;
s = strchr(cmd, '.');
off = (int)simple_strtoul(argv[2], NULL, 16);
if (s != NULL && strcmp(s, ".oob") == 0)
ret = nand_dump(nand, off, 1);
else
ret = nand_dump(nand, off, 0);
return ret == 0 ? 1 : 0;
}
if (strncmp(cmd, "read", 4) == 0 || strncmp(cmd, "write", 5) == 0) {
//命令是 nand read 和nand write 命令的解析
int read;
if (argc < 4)
goto usage;
addr = (ulong)simple_strtoul(argv[2], NULL, 16);
read = strncmp(cmd, "read", 4) == 0; /* 1 = read, 0 = write */
printf("\nNAND %s: ", read ? "read" : "write");
if (arg_off_size(argc - 3, argv + 3, nand, &off, &size) != 0)
return 1;
s = strchr(cmd, '.');
if (!s || !strcmp(s, ".jffs2") ||
!strcmp(s, ".e") || !strcmp(s, ".i")) {
if (read)
ret = nand_read_skip_bad(nand, off, &size,
(u_char *)addr);
else
ret = nand_write_skip_bad(nand, off, &size,
(u_char *)addr);
} else if (s != NULL && !strcmp(s, ".oob")) {
/* out-of-band data */
mtd_oob_ops_t ops = {
.oobbuf = (u8 *)addr,
.ooblen = size,
.mode = MTD_OOB_RAW
};
if (read)
ret = nand->read_oob(nand, off, &ops);
else
ret = nand->write_oob(nand, off, &ops);
} else {
printf("Unknown nand command suffix '%s'.\n", s);
return 1;
}
printf(" %d bytes %s: %s\n", size,
read ? "read" : "written", ret ? "ERROR" : "OK");
return ret == 0 ? 0 : 1;
}
if (strcmp(cmd, "markbad") == 0) {
addr = (ulong)simple_strtoul(argv[2], NULL, 16);
int ret = nand->block_markbad(nand, addr);
if (ret == 0) {
printf("block 0x%08lx successfully marked as bad\n",
(ulong) addr);
return 0;
} else {
printf("block 0x%08lx NOT marked as bad! ERROR %d\n",
(ulong) addr, ret);
}
return 1;
}
if (strcmp(cmd, "biterr") == 0) {
/* todo */
return 1;
}
if (strcmp(cmd, "lock") == 0) {
int tight = 0;
int status = 0;
if (argc == 3) {
if (!strcmp("tight", argv[2]))
tight = 1;
if (!strcmp("status", argv[2]))
status = 1;
}
/*
* ! BROKEN !
*
* TODO: must be implemented and tested by someone with HW
*/
#if 0
if (status) {
ulong block_start = 0;
ulong off;
int last_status = -1;
struct nand_chip *nand_chip = nand->priv;
/* check the WP bit */
nand_chip->cmdfunc (nand, NAND_CMD_STATUS, -1, -1);
printf("device is %swrite protected\n",
(nand_chip->read_byte(nand) & 0x80 ?
"NOT " : ""));
for (off = 0; off < nand->size; off += nand->writesize) {
int s = nand_get_lock_status(nand, off);
/* print message only if status has changed
* or at end of chip
*/
if (off == nand->size - nand->writesize
|| (s != last_status && off != 0)) {
printf("%08lx - %08lx: %8d pages %s%s%s\n",
block_start,
off-1,
(off-block_start)/nand->writesize,
((last_status & NAND_LOCK_STATUS_TIGHT) ? "TIGHT " : ""),
((last_status & NAND_LOCK_STATUS_LOCK) ? "LOCK " : ""),
((last_status & NAND_LOCK_STATUS_UNLOCK) ? "UNLOCK " : ""));
}
last_status = s;
}
} else {
if (!nand_lock(nand, tight)) {
puts("NAND flash successfully locked\n");
} else {
puts("Error locking NAND flash\n");
return 1;
}
}
#endif
return 0;
}
if (strcmp(cmd, "unlock") == 0) {
if (arg_off_size(argc - 2, argv + 2, nand, &off, &size) < 0)
return 1;
/*
* ! BROKEN !
*
* TODO: must be implemented and tested by someone with HW
*/
#if 0
if (!nand_unlock(nand, off, size)) {
puts("NAND flash successfully unlocked\n");
} else {
puts("Error unlocking NAND flash, "
"write and erase will probably fail\n");
return 1;
}
#endif
return 0;
}
usage:
printf("Usage:\n%s\n", cmdtp->usage);
return 1;
}
**********************************************************************************************************************************
bootm命令
bootm命令的實現
/* common/cmd_bootm.c */
int do_bootm (cmd_tbl_t *cmdtp, int flag, int argc, char *argv[])
{
…… ……
/* 檢查頭部 */
if (crc32 (0, (uchar *)data, len) != checksum) {
puts ("Bad Header Checksum\n");
SHOW_BOOT_PROGRESS (-2);
return 1;
}
…… ……
/*解壓縮*/
switch (hdr->ih_comp) {
case IH_COMP_NONE:
if(ntohl(hdr->ih_load) == addr) {
printf (" XIP %s ... ", name);
} else {
#if defined(CONFIG_HW_WATCHDOG) || defined(CONFIG_WATCHDOG)
size_t l = len;
void *to = (void *)ntohl(hdr->ih_load);
void *from = (void *)data;
printf (" Loading %s ... ", name);
while (l > 0) {
size_t tail = (l > CHUNKSZ) ? CHUNKSZ : l;
WATCHDOG_RESET();
memmove (to, from, tail);
to += tail;
from += tail;
l -= tail;
}
#else /* !(CONFIG_HW_WATCHDOG || CONFIG_WATCHDOG) */
memmove ((void *) ntohl(hdr->ih_load), (uchar *)data, len); //將真正的內核移動到加載地址處hdr->ih_load
#endif /* CONFIG_HW_WATCHDOG || CONFIG_WATCHDOG */
}
break;
case IH_COMP_GZIP:
printf (" Uncompressing %s ... ", name);
if (gunzip ((void *)ntohl(hdr->ih_load), unc_len,
(uchar *)data, &len) != 0) {
puts ("GUNZIP ERROR - must RESET board to recover\n");
SHOW_BOOT_PROGRESS (-6);
do_reset (cmdtp, flag, argc, argv);
}
break;
#ifdef CONFIG_BZIP2
case IH_COMP_BZIP2:
printf (" Uncompressing %s ... ", name);
/*
* If we've got less than 4 MB of malloc() space,
* use slower decompression algorithm which requires
* at most 2300 KB of memory.
*/
i = BZ2_bzBuffToBuffDecompress ((char*)ntohl(hdr->ih_load),
&unc_len, (char *)data, len,
CFG_MALLOC_LEN < (4096 * 1024), 0);
if (i != BZ_OK) {
printf ("BUNZIP2 ERROR %d - must RESET board to recover\n", i);
SHOW_BOOT_PROGRESS (-6);
udelay(100000);
do_reset (cmdtp, flag, argc, argv);
}
break;
#endif /* CONFIG_BZIP2 */
default:
if (iflag)
enable_interrupts();
printf ("Unimplemented compression type %d\n", hdr->ih_comp);
SHOW_BOOT_PROGRESS (-7);
return 1;
}
}
…… …… ……
switch (hdr->ih_os) {
default: /* handled by (original) Linux case */
case IH_OS_LINUX: //驚奇!!!!!!!!!!!!!!!!!!!在這裏調用了do_bootm_linux函數
do_bootm_linux (cmdtp, flag, argc, argv,
addr, len_ptr, verify);
break;
case IH_OS_NETBSD:
do_bootm_netbsd (cmdtp, flag, argc, argv,
addr, len_ptr, verify);
break;
case IH_OS_RTEMS:
do_bootm_rtems (cmdtp, flag, argc, argv,
addr, len_ptr, verify);
break;
case IH_OS_VXWORKS:
do_bootm_vxworks (cmdtp, flag, argc, argv,
addr, len_ptr, verify);
break;
case IH_OS_QNX:
do_bootm_qnxelf (cmdtp, flag, argc, argv,
addr, len_ptr, verify);
break;
}
bootm命令調用do_bootm函數。這個函數專門用來引導各種操作系統映像,可以支持引導Linux、vxWorks、QNX等操作系統。引導Linux的時候,調用do_bootm_linux() 函數。
bootm命令主要做三件事情:
1,解析uImage頭部信息,獲取image_header結構體
2,將真正的內核移動到加載地址處,如果相等就不用移動
3,根據操作系統,選擇啓動內核的函數,如do_bootm_linux函數
3.do_bootm_linux函數的實現
/* lib_arm/armlinux.c */
void do_bootm_linux (cmd_tbl_t *cmdtp, int flag, int argc, char *argv[],
ulong addr, ulong *len_ptr, int verify)
{
theKernel = (void (*)(int, int, uint))ntohl(hdr->ih_ep);
… … … …
/* we assume that the kernel is in place */
printf ("\nStarting kernel ...\n\n");
… … … …
theKernel (0, bd->bi_arch_number, bd->bi_boot_params); /*啓動內核,傳遞啓動參數*/
}
do_bootm_linux()函數是專門引導Linux映像的函數,它還可以處理ramdisk文件系統的映像。這裏引導的內核映像和ramdisk映像,必須是U-Boot格式的。
U-Boot格式的映像可以通過mkimage工具來轉換,其中包含了U-Boot可以識別的符號。
以下是bootm.c裏的do_bootm_linux的源碼
int do_bootm_linux(int flag, int argc, char *argv[], bootm_headers_t *images)
{
bd_t *bd = gd->bd;
char *s;
int machid = bd->bi_arch_number; //機器ID
void (*theKernel)(int zero, int arch, uint params);
#ifdef CONFIG_CMDLINE_TAG
char *commandline = getenv ("bootargs"); //獲取啓動參數的命令行
#endif
theKernel = (void (*)(int, int, uint))images->ep; // the_kernel即鏡像文件的入口地址
s = getenv ("machid");
if (s) {
machid = simple_strtoul (s, NULL, 16);
printf ("Using machid 0x%x from environment\n", machid);
}
show_boot_progress (15);
debug ("## Transferring control to Linux (at address %08lx) ...\n",
(ulong) theKernel);
#if defined (CONFIG_SETUP_MEMORY_TAGS) || \ //以下是設立標籤,在啓動內核之前,交給內核的參數
defined (CONFIG_CMDLINE_TAG) || \
defined (CONFIG_INITRD_TAG) || \
defined (CONFIG_SERIAL_TAG) || \
defined (CONFIG_REVISION_TAG) || \
defined (CONFIG_LCD) || \
defined (CONFIG_VFD)
setup_start_tag (bd);
#ifdef CONFIG_SERIAL_TAG
setup_serial_tag (¶ms);
#endif
#ifdef CONFIG_REVISION_TAG
setup_revision_tag (¶ms);
#endif
#ifdef CONFIG_SETUP_MEMORY_TAGS
setup_memory_tags (bd); //設置內存TAG,會用到bd->bi_dram[].start bd->bi_dram[].size
#endif
#ifdef CONFIG_CMDLINE_TAG
setup_commandline_tag (bd, commandline);
#endif
#ifdef CONFIG_INITRD_TAG
if (images->rd_start && images->rd_end)
setup_initrd_tag (bd, images->rd_start, images->rd_end);
#endif
#if defined (CONFIG_VFD) || defined (CONFIG_LCD)
setup_videolfb_tag ((gd_t *) gd);
#endif
setup_end_tag (bd);
#endif
/* we assume that the kernel is in place */
printf ("\nStarting kernel ...\n\n");
#ifdef CONFIG_USB_DEVICE
{
extern void udc_disconnect (void);
udc_disconnect ();
}
#endif
cleanup_before_linux ();
theKernel (0, machid, bd->bi_boot_params); //啓動內核,一去不復返
/* does not return */
return 1;
}
第二階段小結: bootcmd
主要是3個關鍵函數 start_armboot ----> main_loop ------> do_bootm_linux
當我們在倒數計時時按下空格鍵進入uboot命令界面,我們若輸入boot命令回車,便會調用bootcmd環境變量的兩條指令,同樣啓動內核
我們按下空格時出現的菜單 是需要自己去實現的,在common裏創建一個新文件cmd_menu.c裏去實現