uboot-tiny4412启动流程(下)----如何将自己的裸板测试程序加入uboot中启动测试

今天在工作上搞了一天高通的芯片uboot程序，目的是希望将一个裸板的程序移植到uboot中，并且开机让它运行。这个芯片是NXP4330,目前是高通的一个芯片，基于ARM-contexA9架构，那么就跟4412是一样的架构了，今天将uboot加载流程基本上算是搞明白了，也明白了uboot最后是通过一些手段，最终能够去加载kernel.img，最终启动内核，后面就是加载文件系统了。

心血来潮，所以，今天借这个机会在说明一下4412的uboot最后是怎么去获取kernel.img进而启动,其实都大同小异，搞明白一个其它的就类似的了。

以前有写过一篇文章，关于4412的uboot启动流程的汇编分析:http://blog.csdn.net/morixinguan

在这篇文章中，我们分析了4412 uboot的核心，最后通过以下代码调用了C中的函数:

这就算是完成了uboot启动的第一个阶段:

start_code -> cpu_init_crit -> call_board_init_f -> board_init_f

call_board_init_f:
	ldr	sp, =(CONFIG_SYS_INIT_SP_ADDR)
	bic	sp, sp, #7 /* 8-byte alignment for ABI compliance */
	ldr	r0,=0x00000000
	bl	board_init_f

从代码中我们可以看到，程序最终是bl board_init_f,跳转到这个函数去执行，我们跟到这个函数如下:

它的位置位于arch/arm/lib/board.c

void board_init_f(ulong bootflag)
{
	bd_t *bd;
	init_fnc_t **init_fnc_ptr;
	gd_t *id;
	ulong addr, addr_sp;

	/* Pointer is writable since we allocated a register for it */
	gd = (gd_t *) ((CONFIG_SYS_INIT_SP_ADDR) & ~0x07);

	/* compiler optimization barrier needed for GCC >= 3.4 */
	__asm__ __volatile__("": : :"memory");

	memset((void*)gd, 0, sizeof (gd_t));

	gd->mon_len = _bss_end_ofs;

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

	debug ("monitor len: %08lX\n", gd->mon_len);
	/*
	 * Ram is setup, size stored in gd !!
	 */
	debug ("ramsize: %08lX\n", gd->ram_size);
#if defined(CONFIG_SYS_MEM_TOP_HIDE)
	/*
	 * Subtract specified amount of memory to hide so that it won't
	 * get "touched" at all by U-Boot. By fixing up gd->ram_size
	 * the Linux kernel should now get passed the now "corrected"
	 * memory size and won't touch it either. This should work
	 * for arch/ppc and arch/powerpc. Only Linux board ports in
	 * arch/powerpc with bootwrapper support, that recalculate the
	 * memory size from the SDRAM controller setup will have to
	 * get fixed.
	 */
	gd->ram_size -= CONFIG_SYS_MEM_TOP_HIDE;
#endif

	addr = CONFIG_SYS_SDRAM_BASE + gd->ram_size;

#ifdef CONFIG_LOGBUFFER
#ifndef CONFIG_ALT_LB_ADDR
	/* reserve kernel log buffer */
	addr -= (LOGBUFF_RESERVE);
	debug ("Reserving %dk for kernel logbuffer at %08lx\n", LOGBUFF_LEN, addr);
#endif
#endif

#ifdef CONFIG_PRAM
	/*
	 * reserve protected RAM
	 */
	i = getenv_r("pram", (char *)tmp, sizeof (tmp));
	reg = (i > 0) ? simple_strtoul((const char *)tmp, NULL, 10) : CONFIG_PRAM;
	addr -= (reg << 10);		/* size is in kB */
	debug ("Reserving %ldk for protected RAM at %08lx\n", reg, addr);
#endif /* CONFIG_PRAM */

#if !(defined(CONFIG_SYS_NO_ICACHE) && defined(CONFIG_SYS_NO_DCACHE))
	/* reserve TLB table */
	addr -= (4096 * 4);

	/* round down to next 64 kB limit */
	addr &= ~(0x10000 - 1);

	gd->tlb_addr = addr;
	debug ("TLB table at: %08lx\n", addr);
#endif

	/* round down to next 4 kB limit */
	addr &= ~(4096 - 1);
	debug ("Top of RAM usable for U-Boot at: %08lx\n", addr);

#ifdef CONFIG_VFD
#	ifndef PAGE_SIZE
#	  define PAGE_SIZE 4096
#	endif
	/*
	 * reserve memory for VFD display (always full pages)
	 */
	addr -= vfd_setmem(addr);
	gd->fb_base = addr;
#endif /* CONFIG_VFD */

#ifdef CONFIG_LCD
	/* reserve memory for LCD display (always full pages) */
	addr = lcd_setmem(addr);
	gd->fb_base = addr;
#endif /* CONFIG_LCD */

	/*
	 * reserve memory for U-Boot code, data & bss
	 * round down to next 4 kB limit
	 */
	addr -= gd->mon_len;
	addr &= ~(4096 - 1);

#if defined(CONFIG_S5P) || defined(CONFIG_S5P6450)
	addr = CONFIG_SYS_LOAD_ADDR;
#endif

	debug ("Reserving %ldk for U-Boot at: %08lx\n", gd->mon_len >> 10, addr);

#ifndef CONFIG_PRELOADER
	/*
	 * reserve memory for malloc() arena
	 */
	addr_sp = addr - TOTAL_MALLOC_LEN;
	debug ("Reserving %dk for malloc() at: %08lx\n",
			TOTAL_MALLOC_LEN >> 10, addr_sp);
	/*
	 * (permanently) allocate a Board Info struct
	 * and a permanent copy of the "global" data
	 */
	addr_sp -= sizeof (bd_t);
	bd = (bd_t *) addr_sp;
	gd->bd = bd;
	debug ("Reserving %zu Bytes for Board Info at: %08lx\n",
			sizeof (bd_t), addr_sp);
	addr_sp -= sizeof (gd_t);
	id = (gd_t *) addr_sp;
	debug ("Reserving %zu Bytes for Global Data at: %08lx\n",
			sizeof (gd_t), addr_sp);

	/* setup stackpointer for exeptions */
	gd->irq_sp = addr_sp;
#ifdef CONFIG_USE_IRQ
	addr_sp -= (CONFIG_STACKSIZE_IRQ+CONFIG_STACKSIZE_FIQ);
	debug ("Reserving %zu Bytes for IRQ stack at: %08lx\n",
		CONFIG_STACKSIZE_IRQ+CONFIG_STACKSIZE_FIQ, addr_sp);
#endif

	/* leave 3 words for abort-stack    */
	addr_sp -= 3;

	/* 8-byte alignment for ABI compliance */
	addr_sp &= ~0x07;
#else
	addr_sp += 128;	/* leave 32 words for abort-stack   */
	gd->irq_sp = addr_sp;
#endif

	debug ("New Stack Pointer is: %08lx\n", addr_sp);

#ifdef CONFIG_POST
	post_bootmode_init();
	post_run(NULL, POST_ROM | post_bootmode_get(0));
#endif

	gd->bd->bi_baudrate = gd->baudrate;
	/* Ram ist board specific, so move it to board code ... */
	dram_init_banksize();
	display_dram_config();	/* and display it */

	gd->relocaddr = addr;
	gd->start_addr_sp = addr_sp;
	gd->reloc_off = addr - _TEXT_BASE;
	debug ("relocation Offset is: %08lx\n", gd->reloc_off);
	memcpy(id, (void *)gd, sizeof (gd_t));

	relocate_code(addr_sp, id, addr);
	/* NOTREACHED - relocate_code() does not return */
}

第二阶段的起始代码 arch/arm/lib/board.c 里的 void board_init_r(gd_t *id, ulong dest_addr) 函数

其中， id 是从 board_init_f 里面获取,dest_addr也就是链接u-boot的地址

void board_init_r(gd_t *id, ulong dest_addr)
{
	char *s;
	bd_t *bd;
	ulong malloc_start;
#if !defined(CONFIG_SYS_NO_FLASH)
	ulong flash_size;
#endif

	gd = id;
	bd = gd->bd;

	gd->flags |= GD_FLG_RELOC;	/* tell others: relocation done */

	monitor_flash_len = _bss_start_ofs;
	debug ("monitor flash len: %08lX\n", monitor_flash_len);
	board_init();	/* Setup chipselects */

#ifdef CONFIG_SERIAL_MULTI
	//serial_initialize();
#endif

	debug ("Now running in RAM - U-Boot at: %08lx\n", dest_addr);

#ifdef CONFIG_LOGBUFFER
	logbuff_init_ptrs();
#endif
#ifdef CONFIG_POST
	post_output_backlog();
#endif
        //这里对内存进行了分配
	/* The Malloc area is immediately below the monitor copy in DRAM */
	malloc_start = dest_addr - TOTAL_MALLOC_LEN;
	mem_malloc_init(malloc_start, TOTAL_MALLOC_LEN);

#if !defined(CONFIG_SYS_NO_FLASH)
	puts("FLASH:\t");

	if ((flash_size = flash_init()) > 0) {
# ifdef CONFIG_SYS_FLASH_CHECKSUM
		print_size(flash_size, "");
		/*
		 * Compute and print flash CRC if flashchecksum is set to 'y'
		 *
		 * NOTE: Maybe we should add some WATCHDOG_RESET()? XXX
		 */
		s = getenv("flashchecksum");
		if (s && (*s == 'y')) {
			printf("  CRC: %08X",
				crc32 (0, (const unsigned char *) CONFIG_SYS_FLASH_BASE, flash_size)
			);
		}
		putc('\n');
# else	/* !CONFIG_SYS_FLASH_CHECKSUM */
		print_size(flash_size, "\n");
# endif /* CONFIG_SYS_FLASH_CHECKSUM */
	} else {
		puts(failed);
		hang();
	}
#endif

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

#if defined(CONFIG_CMD_ONENAND)
	onenand_init();
#endif

#ifdef CONFIG_GENERIC_MMC
	mmc_initialize(bd);
#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 */

	/* 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

	 /* set up exceptions */
	interrupt_init();
	/* enable exceptions */
	enable_interrupts();

	/* Perform network card initialisation if necessary */
#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 */

#if defined(CONFIG_DRIVER_DM9000)
	/* XXX: this needs to be moved to board init */
	if (getenv("ethaddr")) {
		uchar enetaddr[6];
		eth_getenv_enetaddr("ethaddr", enetaddr);
		dm9000_set_mac_addr(enetaddr);
	}
#endif

	/* 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

#ifdef CONFIG_BITBANGMII
	bb_miiphy_init();
#endif
#if defined(CONFIG_CMD_NET)
#if defined(CONFIG_NET_MULTI)
	puts("Net:\t");
#endif
	eth_initialize(gd->bd);
#if defined(CONFIG_RESET_PHY_R)
	debug ("Reset Ethernet PHY\n");
	reset_phy();
#endif
#endif

#ifdef CONFIG_POST
	post_run(NULL, POST_RAM | post_bootmode_get(0));
#endif

#if defined(CONFIG_PRAM) || defined(CONFIG_LOGBUFFER)
	/*
	 * Export available size of memory for Linux,
	 * taking into account the protected RAM at top of memory
	 */
	{
		ulong pram;
		uchar memsz[32];
#ifdef CONFIG_PRAM
		char *s;

		if ((s = getenv("pram")) != NULL) {
			pram = simple_strtoul(s, NULL, 10);
		} else {
			pram = CONFIG_PRAM;
		}
#else
		pram=0;
#endif
#ifdef CONFIG_LOGBUFFER
#ifndef CONFIG_ALT_LB_ADDR
		/* Also take the logbuffer into account (pram is in kB) */
		pram += (LOGBUFF_LEN+LOGBUFF_OVERHEAD)/1024;
#endif
#endif
		sprintf((char *)memsz, "%ldk", (bd->bi_memsize / 1024) - pram);
		setenv("mem", (char *)memsz);
	}
#endif
	//从这里开始就进入了uboot的死循环，这里就是所谓的uboot main函数了
	/* 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 */
}

由于上面代码过多，我们从代码的注释大致就可以看出，上面是对串口，内存，以及平台相关的东西进行了设置和初始化，到代码的最后我们看到了以下死循环:

for (;;) {
		main_loop();
	}

我们接着跟到main_loop()；这个函数:

这个函数的位置位于:common/main.c

main_loop()函数做的都是与具体平台无关的工作，主要包括初始化启动次数限制机制、设置软件版本号、打印启动信息、解析命令等。

（1）设置启动次数有关参数。在进入main_loop()函数后，首先是根据配置加载已经保留的启动次数，并且根据配置判断是否超过启动次数。代码如下：

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 */

#ifdef CONFIG_BOOTCOUNT_LIMIT
	bootcount = bootcount_load();  // 加载保存的启动次数
	bootcount++;		// 启动次数加1
	bootcount_store (bootcount);  // 更新启动次数
	sprintf (bcs_set, "%lu", bootcount);// 打印启动次数  
	setenv ("bootcount", bcs_set);
	bcs = getenv ("bootlimit"); //获取环境变量,用于引导
	bootlimit = bcs ? simple_strtoul (bcs, NULL, 10) : 0;
#endif /* CONFIG_BOOTCOUNT_LIMIT */

#ifdef CONFIG_MODEM_SUPPORT
	debug ("DEBUG: main_loop:   do_mdm_init=%d\n", do_mdm_init);
	if (do_mdm_init) {
		char *str = strdup(getenv("mdm_cmd"));// 获取Modem参数
		setenv ("preboot", str);  /* set or delete definition */ //设置环境变量
		if (str != NULL)
			free (str);
		mdm_init(); /* wait for modem connection */
	}
#endif  /* CONFIG_MODEM_SUPPORT */
//接下来设置U-Boot的版本号，初始化命令自动完成功能等。代码如下：
#ifdef CONFIG_VERSION_VARIABLE
	{
		extern char version_string[];

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

#ifdef CONFIG_SYS_HUSH_PARSER
	u_boot_hush_start ();//初始化hash功能

#endif

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

#ifdef CONFIG_AUTO_COMPLETE
	install_auto_complete(); // 初始化命令自动完成功能
#endif

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

# ifndef CONFIG_SYS_HUSH_PARSER
		run_command (p, 0);// 运行Boot参数  
# else
		parse_string_outer(p, FLAG_PARSE_SEMICOLON |
				    FLAG_EXIT_FROM_LOOP);
# endif

# ifdef CONFIG_AUTOBOOT_KEYED
		disable_ctrlc(prev);	/* restore Control C checking */ // 恢复Ctrl+C组合键
# endif
	}
#endif /* CONFIG_PREBOOT */

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

#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);

# 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)) { // 检查是否超出启动次数限制
		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) { // 检查是否支持菜单键  
	    s = getenv("menucmd");
	    if (s) {
# ifndef CONFIG_SYS_HUSH_PARSER
		run_command (s, 0);
# else
		parse_string_outer(s, FLAG_PARSE_SEMICOLON |
				    FLAG_EXIT_FROM_LOOP);
# endif
	    }
	}
#endif /* CONFIG_MENUKEY */
#endif /* CONFIG_BOOTDELAY */

	/*
	 * 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);// 读取命令  

		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 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);// 运行命令  

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

至此，uboot的加载流程大致就清楚了，如果我的硬件裸板测试程序要移植到uboot里面，然后将uboot重新启动，直接到裸板的测试程序，我们就可以利用上面这个机制，可以将所有的main_loop();函数的代码都去除，然后将硬件测试程序放在main_loop中，因为它是一个死循环，因此会周而复始的进行。