uboot移植之uboot stage2

从stage1的start.S中跳转到uboot/lib_arm/board.c的start_armboot函数，此时处于stage2，已经在sdram的33f80000地址空间内运行，进行cpu及外设的全面初始化
board.c的源码如下

/*
 * (C) Copyright 2002-2006
 * Wolfgang Denk,DENX Software Engineering,wd@denx.de.
 *
 * (C) Copyright 2002
 * Sysgo Real-Time Solutions,GmbH <www.elinos.com>
 * Marius Groeger <mgroeger@sysgo.de>
 *
 * See file CREDITS for list of people who contributed to this
 * project.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License as
 * published by the Free Software Foundation; either version 2 of
 * the License,or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,* but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not,write to the Free Software
 * Foundation,Inc.,59 Temple Place,Suite 330,Boston,* MA 02111-1307 USA
 */

/*
 * To match the U-Boot user interface on ARM platforms to the U-Boot
 * standard (as on PPC platforms),some messages with debug character
 * are removed from the default U-Boot build.
 *
 * Define DEBUG here if you want additional info as shown below
 * printed upon startup:
 *
 * U-Boot code: 00F00000 -> 00F3C774  BSS: -> 00FC3274
 * IRQ Stack: 00ebff7c
 * FIQ Stack: 00ebef7c
 */

#include <common.h>
#include <command.h>
#include <malloc.h>
#include <stdio_dev.h>
#include <timestamp.h>
#include <version.h>
#include <net.h>
#include <serial.h>
#include <nand.h>
#include <onenand_uboot.h>
#include <mmc.h>
#include <s3c2410.h>    //tekkamanninja

#ifdef CONFIG_BITBANGMII
#include <miiphy.h>
#endif

#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" (" U_BOOT_DATE " - " U_BOOT_TIME ")"CONFIG_IDENT_STRING;

#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

#if 0
/************************************************************************
 * Coloured LED functionality
 ************************************************************************
 * May be supplied by boards if desired
 */
void inline __coloured_LED_init (void) {}
void coloured_LED_init (void) __attribute__((weak,alias("__coloured_LED_init")));
void inline __red_LED_on (void) {}
void red_LED_on (void) __attribute__((weak,alias("__red_LED_on")));
void inline __red_LED_off(void) {}
void red_LED_off(void) __attribute__((weak,alias("__red_LED_off")));
void inline __green_LED_on(void) {}
void green_LED_on(void) __attribute__((weak,alias("__green_LED_on")));
void inline __green_LED_off(void) {}
void green_LED_off(void) __attribute__((weak,alias("__green_LED_off")));
void inline __yellow_LED_on(void) {}
void yellow_LED_on(void) __attribute__((weak,alias("__yellow_LED_on")));
void inline __yellow_LED_off(void) {}
void yellow_LED_off(void) __attribute__((weak,alias("__yellow_LED_off")));
void inline __blue_LED_on(void) {}
void blue_LED_on(void) __attribute__((weak,alias("__blue_LED_on")));
void inline __blue_LED_off(void) {}
void blue_LED_off(void) __attribute__((weak,alias("__blue_LED_off")));
#endif
/************************************************************************
 * Init Utilities							*
 ************************************************************************
 * Some of this code should be moved into the core functions,* or dropped completely,* but let's get it working (again) first...
 */

#if defined(CONFIG_ARM_DCC) && !defined(CONFIG_BAUDRATE)
#define CONFIG_BAUDRATE 115200
#endif
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)
{


#if defined(CONFIG_MINI2440_LED) 	
	struct s3c24x0_gpio * const gpio = s3c24x0_get_base_gpio();
	gpio->GPBDAT = 0x101; //tekkamanninja
#endif

	printf ("nn%snn",version_string);
	printf ("Love Linux forever!!nn");
	debug ("U-Boot code: %08lX -> %08lX  BSS: -> %08lXn",_armboot_start,_bss_start,_bss_end);
#ifdef CONFIG_MODEM_SUPPORT
	debug ("Modem Support enabledn");
#endif
#ifdef CONFIG_USE_IRQ
	debug ("IRQ Stack: %08lxn",IRQ_STACK_START);
	debug ("FIQ Stack: %08lxn",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)
{
	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 CONFIG_SYS_NO_FLASH
static void display_flash_config (ulong size)
{
	puts ("Flash: ");
	print_size (size,"n");
}
#endif /* CONFIG_SYS_NO_FLASH */

#if defined(CONFIG_HARD_I2C) || defined(CONFIG_SOFT_I2C)
static int init_func_i2c (void)
{
	puts ("I2C:   ");
	i2c_init (CONFIG_SYS_I2C_SPEED,CONFIG_SYS_I2C_SLAVE);
	puts ("readyn");
	return (0);
}
#endif

#if defined(CONFIG_CMD_PCI) || defined (CONFIG_PCI)
#include <pci.h>
static int arm_pci_init(void)
{
	pci_init();
	return 0;
}
#endif /* CONFIG_CMD_PCI || CONFIG_PCI */

/*
 * 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);

init_fnc_t *init_sequence[] = {
#if defined(CONFIG_ARCH_CPU_INIT)
	arch_cpu_init,/* basic arch cpu dependent setup */
#endif
	board_init,/* basic board dependent setup */
#if defined(CONFIG_USE_IRQ)
	interrupt_init,/* set up exceptions */
#endif
	timer_init,/* initialize timer */
	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 */
#if defined(CONFIG_CMD_PCI) || defined (CONFIG_PCI)
	arm_pci_init,#endif
	display_dram_config,};

void start_armboot (void)
{
	init_fnc_t **init_fnc_ptr;
	char *s;
#if defined(CONFIG_VFD) || defined(CONFIG_LCD)
	unsigned long addr;
#endif
#if defined(CONFIG_MINI2440_LED) 	
	struct s3c24x0_gpio * const gpio = s3c24x0_get_base_gpio();
#endif
	/* Pointer is writable since we allocated a register for it */
	gd = (gd_t*)(_armboot_start - CONFIG_SYS_MALLOC_LEN - sizeof(gd_t));
	/* compiler optimization barrier needed for GCC >= 3.4 */
	__asm__ __volatile__("": : :"memory");

	memset ((void*)gd,sizeof (gd_t));
	gd->bd = (bd_t*)((char*)gd - sizeof(bd_t));
	memset (gd->bd,sizeof (bd_t));

	gd->flags |= GD_FLG_RELOC;

	monitor_flash_len = _bss_start - _armboot_start;

	for (init_fnc_ptr = init_sequence; *init_fnc_ptr; ++init_fnc_ptr) {
		if ((*init_fnc_ptr)() != 0) {
			hang ();
		}
	}

	/* armboot_start is defined in the board-specific linker script */
	mem_malloc_init (_armboot_start - CONFIG_SYS_MALLOC_LEN,CONFIG_SYS_MALLOC_LEN);

#ifndef CONFIG_SYS_NO_FLASH
	/* configure available FLASH banks */
	display_flash_config (flash_init ());
#endif /* CONFIG_SYS_NO_FLASH */

#ifdef CONFIG_VFD
#	ifndef PAGE_SIZE
#	  define PAGE_SIZE 4096
#	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);
	vfd_setmem (addr);
	gd->fb_base = addr;
#endif /* CONFIG_VFD */

#ifdef CONFIG_LCD
	/* 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);
		lcd_setmem (addr);
		gd->fb_base = addr;
	}
#endif /* CONFIG_LCD */

#if defined(CONFIG_CMD_NAND)
	puts ("NAND:  ");
	nand_init();		/* go init the NAND */
#endif

#if defined(CONFIG_CMD_ONENAND)
	onenand_init();
#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 */

#ifdef CONFIG_SERIAL_MULTI
	serial_initialize();
#endif

	/* IP Address */
	gd->bd->bi_ip_addr = getenv_IPaddr ("ipaddr");

	stdio_init ();	/* get the devices list going. */

	jumptable_init ();

#if defined(CONFIG_API)
	/* Initialize API */
	api_init ();
#endif

	console_init_r ();	/* fully init console as a device */

#if defined(CONFIG_ARCH_MISC_INIT)
	/* miscellaneous arch dependent initialisations */
	arch_misc_init ();
#endif
#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_TI_EMAC
	/* XXX: this needs to be moved to board init */
extern void davinci_eth_set_mac_addr (const u_int8_t *addr);
	if (getenv ("ethaddr")) {
		uchar enetaddr[6];
		eth_getenv_enetaddr("ethaddr",enetaddr);
		davinci_eth_set_mac_addr(enetaddr);
	}
#endif

#if defined(CONFIG_DRIVER_SMC91111) || defined (CONFIG_DRIVER_LAN91C96)
	/* XXX: this needs to be moved to board init */
	if (getenv ("ethaddr")) {
		uchar enetaddr[6];
		eth_getenv_enetaddr("ethaddr",enetaddr);
		smc_set_mac_addr(enetaddr);
	}
#endif /* CONFIG_DRIVER_SMC91111 || CONFIG_DRIVER_LAN91C96 */

	/* Initialize from environment */
	if ((s = getenv ("loadaddr")) != NULL) {
		load_addr = simple_strtoul (s,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

#ifdef CONFIG_GENERIC_MMC
	puts ("MMC:   ");
	mmc_initialize (gd->bd);
#endif

#ifdef CONFIG_BITBANGMII
	bb_miiphy_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 PHYn");
	reset_phy();
#endif
#endif
/****************************lighted led************************************************/
#if defined(CONFIG_MINI2440_LED) 	
		gpio->GPBDAT = 0x0; //tekkamanninja
#endif
 
#if defined(CONFIG_CFB_CONSOLE)        
	printf ("%sn",version_string);
	printf ("modified by tekkamanninjan(tekkamanninja@163.com)n");
	printf ("Love Linux forever!!n");
#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 (;;);
}

line246，数组init_sequence[]中记录了需遍历执行的许多初始化函数，这些函数分布在不同的文件中
其中有位于uboot/board/tekkamanninja/mini2440/mini2440.c中的board_init函数进行初始化mini2440板子
其中有串口和控制台的初始化函数，串口和控制台初始化之前无法打印信息，可以点亮led帮助调试
一下摘自mini2440之U-boot移植详细手册-20100419.pdf? ch6.4.1
在U-boot 启动的第一阶段，初始化了Nand Flash 控制器。但到第二阶段start_armboot
函数还是会再次初始化Nand Flash 控制器。因为第二阶段和第一阶段的代码基本是独立
的，第一阶段的代码基本只起到代码重定位的作用，到了第二阶段才是真正U-boot 的开始，
以前的初始化过程还会重做一遍，比如始化Nand Flash 控制器、CPU 频率等。

在line 463 初始化完成后进入main_loop ();
main_loop函数在uboot/common/main.c中，源码如下

/****************************************************************************/

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_PREBOOT
	char *p;
#endif
#ifdef CONFIG_BOOTCOUNT_LIMIT
	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)
	ulong bmp = 0;		/* default bitmap */
	extern int trab_vfd (ulong bitmap);

#ifdef CONFIG_MODEM_SUPPORT
	if (do_mdm_init)
		bmp = 1;	/* alternate bitmap */
#endif
	trab_vfd (bmp);
#endif	/* CONFIG_VFD && VFD_TEST_LOGO */

#if defined(CONFIG_UPDATE_TFTP)
	update_tftp ();
#endif /* CONFIG_UPDATE_TFTP */

#ifdef CONFIG_BOOTCOUNT_LIMIT
	bootcount = bootcount_load();
	bootcount++;
	bootcount_store (bootcount);
	sprintf (bcs_set,"%lu",bootcount);
	setenv ("bootcount",bcs_set);
	bcs = getenv ("bootlimit");
	bootlimit = bcs ? simple_strtoul (bcs,10) : 0;
#endif /* CONFIG_BOOTCOUNT_LIMIT */

#ifdef CONFIG_MODEM_SUPPORT
	debug ("DEBUG: main_loop:   do_mdm_init=%dn",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
	{
		extern char version_string[];

		setenv ("ver",version_string);  /* set version variable */
	}
#endif /* CONFIG_VERSION_VARIABLE */

#ifdef CONFIG_SYS_HUSH_PARSER
	u_boot_hush_start ();
#endif

#if defined(CONFIG_HUSH_INIT_VAR)
	hush_init_var ();
#endif

#ifdef CONFIG_AUTO_COMPLETE
	install_auto_complete();
#endif

#ifdef CONFIG_PREBOOT
	if ((p = getenv ("preboot")) != NULL) {
# ifdef CONFIG_AUTOBOOT_KEYED
		int prev = disable_ctrlc(1);	/* disable Control C checking */
# endif

# ifndef CONFIG_SYS_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");
	bootdelay = s ? (int)simple_strtol(s,10) : CONFIG_BOOTDELAY;

	debug ("### main_loop entered: bootdelay=%dnn",bootdelay);

# ifdef CONFIG_BOOT_RETRY_TIME
	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
	if (bootlimit && (bootcount > bootlimit)) {
		printf ("Warning: Bootlimit (%u) exceeded. Using altbootcmd.n",(unsigned)bootlimit);
		s = getenv ("altbootcmd");
	}
	else
#endif /* CONFIG_BOOTCOUNT_LIMIT */
		s = getenv ("bootcmd");

	debug ("### main_loop: bootcmd="%s"n",s ? s : "<UNDEFINED>");

	if (bootdelay >= 0 && s && !abortboot (bootdelay)) {
# ifdef CONFIG_AUTOBOOT_KEYED
		int prev = disable_ctrlc(1);	/* disable Control C checking */
# endif

# ifndef CONFIG_SYS_HUSH_PARSER
		run_command (s,0);
# 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");
	    if (s) {
# ifndef CONFIG_SYS_HUSH_PARSER
		run_command (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
	 */
#ifdef CONFIG_SYS_HUSH_PARSER
	parse_file_outer();
	/* This point is never reached */
	for (;;);
#else
	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 (CONFIG_SYS_PROMPT);

		flag = 0;	/* assume no special flags for now */
		if (len > 0)
			strcpy (lastcommand,console_buffer);
		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 commandn");
# ifdef CONFIG_RESET_TO_RETRY
			/* Reinit board to run initialization code again */
			do_reset (NULL,NULL);
# else
			return;		/* retry autoboot */
# endif
		}
#endif

		if (len == -1)
			puts ("<INTERRUPT>n");
		else
			rc = run_command (lastcommand,flag);

		if (rc <= 0) {
			/* invalid command or not repeatable,forget it */
			lastcommand[0] = 0;
		}
	}
#endif /*CONFIG_SYS_HUSH_PARSER*/
}

#ifdef CONFIG_BOOT_RETRY_TIME
/***************************************************************************

进入类似shell的命令提示符后，
可以输入bootm命令来加载内核,
bootm命令实现在common/cmd_boot.c中，具体是:

U_BOOT_CMD(
	bootm,CONFIG_SYS_MAXARGS,1,do_bootm,"boot application image from memory","[addr [arg ...]]n    - boot application image stored in memoryn"
	"tpassing arguments 'arg ...'; when booting a Linux kernel,n"
	"t'arg' can be the address of an initrd imagen"
#if defined(CONFIG_OF_LIBFDT)
	"tWhen booting a Linux kernel which requires a flat device-treen"
	"ta third argument is required which is the address of then"
	"tdevice-tree blob. To boot that kernel without an initrd image,n"
	"tuse a '-' for the second argument. If you do not pass a thirdn"
	"ta bd_info struct will be passed insteadn"
#endif
#if defined(CONFIG_FIT)
	"tnFor the new multi component uImage format (FIT) addressesn"
	"tmust be extened to include component or configuration unit name:n"
	"taddr:<subimg_uname> - direct component image specificationn"
	"taddr#<conf_uname>   - configuration specificationn"
	"tUse iminfo command to get the list of existing componentn"
	"timages and configurations.n"
#endif
	"nSub-commands to do part of the bootm sequence.  The sub-commands "
	"must ben"
	"issued in the order below (it's ok to not issue all sub-commands):n"
	"tstart [addr [arg ...]]n"
	"tloados  - load OS imagen"
#if defined(CONFIG_PPC) || defined(CONFIG_M68K) || defined(CONFIG_SPARC)
	"tramdisk - relocate initrd,set env initrd_start/initrd_endn"
#endif
#if defined(CONFIG_OF_LIBFDT)
	"tfdt     - relocate flat device treen"
#endif
	"tcmdline - OS specific command line processing/setupn"
	"tbdt     - OS specific bd_t processingn"
	"tprep    - OS specific prep before relocation or gon"
	"tgo      - start OS"
);

/*******************************************************************/
/* bootd - boot default image */
/*******************************************************************/
#if defined(CONFIG_CMD_BOOTD)

bootm会调用do_bootm()函数---->调用lib_arm/bootm.c中的do_bootm_linux()函数---->调用theKernel (0,machid,bd->bi_boot_params);最终载入内核

其中，
machid即设定的板子id，MRCH_TYPE_MINI2440

bd->bi_boot_params即传递给内的参数列表在sdram上存放的位置，为30000100
流程如下

发现在console_init_f初始化串口之前执行printk会使uboot死掉

在调用thekernel之前会打印一行（也是在do_bootm_linux()函数里）：
/* we assume that the kernel is in place */
printf ("nStarting kernel ...nn");

uboot/board/board/tekkamanninja/mini2440/mini2440.c是在第二阶段执行的文件，用于初始化mini2440板子

/*
 * (C) Copyright 2002
 * Sysgo Real-Time Solutions,GmbH <www.elinos.com>
 * Marius Groeger <mgroeger@sysgo.de>
 *
 * (C) Copyright 2002
 * David Mueller,ELSOFT AG,<d.mueller@elsoft.ch>
 *
 * (C) Copyright 2005
 * JinHua Luo,GuangDong Linux Center,<luo.jinhua@gd-linux.com>
 *
 * See file CREDITS for list of people who contributed to this
 * project.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License as
 * published by the Free Software Foundation; either version 2 of
 * the License,* MA 02111-1307 USA
 */

#include <common.h>
#include <netdev.h>
#include <s3c2410.h>
#include <video_fb.h>
#if defined(CONFIG_CMD_NAND)
#include <linux/mtd/nand.h>
#endif

DECLARE_GLOBAL_DATA_PTR;

#define FCLK_SPEED 1

#if FCLK_SPEED==0		/* Fout = 203MHz,Fin = 12MHz for Audio */
#define M_MDIV	0xC3
#define M_PDIV	0x4
#define M_SDIV	0x1
#elif FCLK_SPEED==1		/* Fout = 202.8MHz */

#if defined(CONFIG_S3C2410)
/* Fout = 202.8MHz */
#define M_MDIV	0xA1
#define M_PDIV	0x3
#define M_SDIV	0x1
#endif

#if defined(CONFIG_S3C2440)
/* Fout = 405MHz */
#define M_MDIV 0x7f	
#define M_PDIV 0x2
#define M_SDIV 0x1
#endif
#endif

#define USB_CLOCK 1

#if USB_CLOCK==0
#define U_M_MDIV	0xA1
#define U_M_PDIV	0x3
#define U_M_SDIV	0x1
#elif USB_CLOCK==1

#if defined(CONFIG_S3C2410)
#define U_M_MDIV	0x48
#define U_M_PDIV	0x3
#endif

#if defined(CONFIG_S3C2440)
#define U_M_MDIV 0x38
#define U_M_PDIV 0x2
#endif

#define U_M_SDIV	0x2
#endif

static inline void delay (unsigned long loops)
{
	__asm__ volatile ("1:n"
			  "subs %0,%1,#1n"
			  "bne 1b":"=r" (loops):"0" (loops));
}

/*
 * Miscellaneous platform dependent initialisations
 */

int board_init (void)
{
	struct s3c24x0_clock_power * const clk_power =
					s3c24x0_get_base_clock_power();
	struct s3c24x0_gpio * const gpio = s3c24x0_get_base_gpio();

	/* to reduce PLL lock time,adjust the LOCKTIME register */
	clk_power->LOCKTIME = 0xFFFFFF;

	/* configure MPLL */
	clk_power->MPLLCON = ((M_MDIV << 12) + (M_PDIV << 4) + M_SDIV);

	/* some delay between MPLL and UPLL */
	delay (4000);

	/* configure UPLL */
	clk_power->UPLLCON = ((U_M_MDIV << 12) + (U_M_PDIV << 4) + U_M_SDIV);

	/* some delay between MPLL and UPLL */
	delay (8000);

	/* set up the I/O ports */
	/* set up the I/O ports */
	gpio->GPACON = 0x007FFFFF;

#if defined(CONFIG_MINI2440) 
	gpio->GPBCON = 0x00295551;
#else
	gpio->GPBCON = 0x00044556;
#endif

	gpio->GPBUP = 0x000007FF;

#if defined(CONFIG_MINI2440) 
	gpio->GPCCON = 0xAAAAA6AA;
	gpio->GPCDAT &= ~(1<<5);
#else
	gpio->GPCCON = 0xAAAAAAAA;
#endif
	gpio->GPCUP = 0x0000FFFF;
	gpio->GPDCON = 0xAAAAAAAA;
	gpio->GPDUP = 0xFFFFFFFF;
	gpio->GPECON = 0xAAAAAAAA;
	gpio->GPEUP = 0x0000FFFF;
	gpio->GPFCON = 0x000055AA;
	gpio->GPFUP = 0x000000FF;
	gpio->GPGCON = 0xFF95FF3A;
	gpio->GPGUP = 0x0000FFFF;
	gpio->GPHCON = 0x0016FAAA;
	gpio->GPHUP = 0x000007FF;

	gpio->EXTINT0=0x22222222;
	gpio->EXTINT1=0x22222222;
	gpio->EXTINT2=0x22222222;

	/* arch number of SMDK2410-Board */
#if defined(CONFIG_S3C2410)
	/* arch number of SMDK2410-Board */
	gd->bd->bi_arch_number = MACH_TYPE_SMDK2410;
#endif

#if defined(CONFIG_S3C2440)
/* arch number of S3C2440-Board */
	gd->bd->bi_arch_number = MACH_TYPE_MINI2440 ;//defined in include/asm/mach-types.h,is 1999
#endif


	/* adress of boot parameters */
	gd->bd->bi_boot_params = 0x30000100;

	icache_enable();
	dcache_enable();
#if	defined(CONFIG_MINI2440_LED)
	gpio->GPBDAT = 0x00000181;
#endif
	return 0;
}
/************************************video add by song*****************************************************/
#define MVAL		(0)
#define MVAL_USED 	(0)		//0=each frame   1=rate by MVAL
#define INVVDEN		(1)		//0=normal       1=inverted
#define BSWP		(0)		//Byte swap control
#define HWSWP		(1)		//Half word swap control


//TFT 240320
#define LCD_XSIZE_TFT_240320 	(240)	
#define LCD_YSIZE_TFT_240320 	(320)

//TFT240320
#define HOZVAL_TFT_240320	(LCD_XSIZE_TFT_240320-1)
#define LINEVAL_TFT_240320	(LCD_YSIZE_TFT_240320-1)

//Timing parameter for NEC3.5"
#define VBPD_240320		(3)		
#define VFPD_240320		(10)
#define VSPW_240320		(1)

#define HBPD_240320		(5)
#define HFPD_240320		(2)
#define HSPW_240320_NEC		(36)  //Adjust the horizontal displacement of the screen :tekkamanninja@163.com
#define HSPW_240320_TD		(23)  //64MB nand mini2440 is 36,128MB is 23
				      //+ ： -->    - : <--
#define CLKVAL_TFT_240320	(3) 	
//FCLK=101.25MHz,HCLK=50.625MHz,VCLK=6.33MHz


void board_video_init(GraphicDevice *pGD) 
{ 
	struct s3c24x0_lcd * const lcd	 = s3c24x0_get_base_lcd(); 
	struct s3c2410_nand * const nand = s3c2410_get_base_nand();
    /* FIXME: select LCM type by env variable */ 
	 
	/* Configuration for GTA01 LCM on QT2410 */ 
	lcd->LCDCON1 = 0x00000378; /* CLKVAL=4,BPPMODE=16bpp,TFT,ENVID=0 */ 
	lcd->LCDCON2 = (VBPD_240320<<24)|(LINEVAL_TFT_240320<<14)|(VFPD_240320<<6)|(VSPW_240320); 
	lcd->LCDCON3 = (HBPD_240320<<19)|(HOZVAL_TFT_240320<<8)|(HFPD_240320); 

	if ( (nand->NFCONF) & 0x08 )	{ 
	lcd->LCDCON4 = (MVAL<<8)|(HSPW_240320_TD);
	}
	else	{
	  lcd->LCDCON4 = (MVAL<<8)|(HSPW_240320_NEC);
	}
	
	lcd->LCDCON5 = 0x00000f09; 
	lcd->LPCSEL  = 0x00000000; 
} 
/************************************video add by song*****************************************************/
int dram_init (void)
{
	gd->bd->bi_dram[0].start = PHYS_SDRAM_1;
	gd->bd->bi_dram[0].size = PHYS_SDRAM_1_SIZE;

	return 0;
}
#if 0
#if defined(CONFIG_CMD_NAND)
extern ulong nand_probe(ulong physadr);

static inline void NF_Reset(void)
{
	int i;

	NF_SetCE(NFCE_LOW);
	NF_Cmd(0xFF);		/* reset command */
	for(i = 0; i < 10; i++);	/* tWB = 100ns. */
	NF_WaitRB();		/* wait 200~500us; */
	NF_SetCE(NFCE_HIGH);
}

static inline void NF_Init(void)
{
#if 1
#define TACLS   0
#define TWRPH0  3
#define TWRPH1  0
#else
#define TACLS   0
#define TWRPH0  4
#define TWRPH1  2
#endif

	NF_Conf((1<<15)|(0<<14)|(0<<13)|(1<<12)|(1<<11)|(TACLS<<8)|(TWRPH0<<4)|(TWRPH1<<0));
	/*nand->NFCONF = (1<<15)|(1<<14)|(1<<13)|(1<<12)|(1<<11)|(TACLS<<8)|(TWRPH0<<4)|(TWRPH1<<0); */
	/* 1  1    1     1,1      xxx,r xxx,r xxx */
	/* En 512B 4step ECCR nFCE=H tACLS   tWRPH0   tWRPH1 */

	NF_Reset();
}

void nand_init(void)
{
	struct s3c2410_nand * const nand = s3c2410_get_base_nand();

	NF_Init();
#ifdef DEBUG
	printf("NAND flash probing at 0x%.8lXn",(ulong)nand);
#endif
	printf ("%4lu MBn",nand_probe((ulong)nand) >> 20);
}
#endif
#endif
#ifdef CONFIG_CMD_NET
int board_eth_init(bd_t *bis)
{
	int rc = 0;
#ifdef CONFIG_CS8900
	rc = cs8900_initialize(0,CONFIG_CS8900_BASE);
#endif
#ifdef CONFIG_DRIVER_DM9000
	rc = dm9000_initialize(bis);
#endif
	return rc;
}
#endif