大家好，又见面了，我是你们的朋友全栈君。

  上一节S3C2440移植uboot之新建单板_时钟_SDRAM_串口移植uboot初始化了时钟，配置了支持串口，这一节我们继续修改uboot支持NAND启动。

移植Uboot其他文章链接：

S3C2440移植uboot之编译烧写uboot

S3C2440移植uboot之新建单板_时钟_SDRAM_串口

S3C2440移植uboot之启动过程概述

S3C2440移植uboot之支持NAND启动

S3C2440移植uboot之支持NORFLASH

S3C2440移植uboot之支持NANDFLASH操作

S3C2440移植uboot之支持DM9000

S3C2440移植uboot之裁剪和修改默认参数

S3C2440移植uboot之支持烧写yaffs映像及制作补丁

1.去掉 “-pie”选项

  参考之前uboot使用的start.S, init.c来修改uboot代码新的uboot链接地址位于0,且在arm-linux-ld时加了”-pie”选项, 使得u-boot.bin里多了"*(.rel*)", "*(.dynsym)",从而程序非常大,不利于从NAND启动(重定位之前的启动代码应该少于4K).
  所以接下来修改代码,并取消”-pie”选项.
  使用grep “-pie” * -nR找到:

arch/arm/config.mk:75:LDFLAGS_u-boot += -pie             // LDFLAGS: arm-linux-ld的参数

  所以屏蔽arch/arm/config.mk文件的”LDFLAGS_u-boot += -pie”这行即可

2.修改之前的init.c

  将以前写uboot里的init.c放入board/samsung/smdk2440目录, 并检查是否有同名函数名,若函数只在同文件使用,则添加static.并修改Makefile 增加对init.c的支持

vi board/samsung/smdk2440/Makefile 

  修改include/configs/smdk2440.h文件，将CONFIG_SYS_TEXT_BASE宏改为0x33f80000,也就是uboot重定位后的位置, 这里留了512K空间供给uboot重定位
修改完的代码如下所示

/* NAND FLASH控制器 */
#define NFCONF (*((volatile unsigned long *)0x4E000000))
#define NFCONT (*((volatile unsigned long *)0x4E000004))
#define NFCMMD (*((volatile unsigned char *)0x4E000008))
#define NFADDR (*((volatile unsigned char *)0x4E00000C))
#define NFDATA (*((volatile unsigned char *)0x4E000010))
#define NFSTAT (*((volatile unsigned char *)0x4E000020))

/* GPIO */
#define GPHCON (*(volatile unsigned long *)0x56000070)
#define GPHUP (*(volatile unsigned long *)0x56000078)

/* UART registers*/
#define ULCON0 (*(volatile unsigned long *)0x50000000)
#define UCON0 (*(volatile unsigned long *)0x50000004)
#define UFCON0 (*(volatile unsigned long *)0x50000008)
#define UMCON0 (*(volatile unsigned long *)0x5000000c)
#define UTRSTAT0 (*(volatile unsigned long *)0x50000010)
#define UTXH0 (*(volatile unsigned char *)0x50000020)
#define URXH0 (*(volatile unsigned char *)0x50000024)
#define UBRDIV0 (*(volatile unsigned long *)0x50000028)

#define TXD0READY (1<<2)


void nand_read_ll(unsigned int addr, unsigned char *buf, unsigned int len);


static int isBootFromNorFlash(void)
{ 
   
	volatile int *p = (volatile int *)0;
	int val;

	val = *p;
	*p = 0x12345678;
	if (*p == 0x12345678)
	{ 
   
		/* 写成功, 是nand启动 */
		*p = val;
		return 0;
	}
	else
	{ 
   
		/* NOR不能像内存一样写 */
		return 1;
	}
}

void copy_code_to_sdram(unsigned char *src, unsigned char *dest, unsigned int len)
{ 
   	
	int i = 0;
	
	/* 如果是NOR启动 */
	if (isBootFromNorFlash())
	{ 
   
		while (i < len)
		{ 
   
			dest[i] = src[i];
			i++;
		}
	}
	else
	{ 
   
		//nand_init();
		nand_read_ll((unsigned int)src, dest, len);
	}
}

void clear_bss(void)
{ 
   
	extern int __bss_start, __bss_end__;
	int *p = &__bss_start;
	
	for (; p < &__bss_end__; p++)
		*p = 0;
}

void nand_init_ll(void)
{ 
   
#define TACLS 0
#define TWRPH0 1
#define TWRPH1 0
	/* 设置时序 */
	NFCONF = (TACLS<<12)|(TWRPH0<<8)|(TWRPH1<<4);
	/* 使能NAND Flash控制器, 初始化ECC, 禁止片选 */
	NFCONT = (1<<4)|(1<<1)|(1<<0);	
}

static void nand_select(void)
{ 
   
	NFCONT &= ~(1<<1);	
}

static void nand_deselect(void)
{ 
   
	NFCONT |= (1<<1);	
}

static void nand_cmd(unsigned char cmd)
{ 
   
	volatile int i;
	NFCMMD = cmd;
	for (i = 0; i < 10; i++);
}

static void nand_addr(unsigned int addr)
{ 
   
	unsigned int col  = addr % 2048;
	unsigned int page = addr / 2048;
	volatile int i;

	NFADDR = col & 0xff;
	for (i = 0; i < 10; i++);
	NFADDR = (col >> 8) & 0xff;
	for (i = 0; i < 10; i++);
	
	NFADDR  = page & 0xff;
	for (i = 0; i < 10; i++);
	NFADDR  = (page >> 8) & 0xff;
	for (i = 0; i < 10; i++);
	NFADDR  = (page >> 16) & 0xff;
	for (i = 0; i < 10; i++);	
}

static void nand_wait_ready(void)
{ 
   
	while (!(NFSTAT & 1));
}

static unsigned char nand_data(void)
{ 
   
	return NFDATA;
}

void nand_read_ll(unsigned int addr, unsigned char *buf, unsigned int len)
{ 
   
	int col = addr % 2048;
	int i = 0;
		
	/* 1. 选中 */
	nand_select();

	while (i < len)
	{ 
   
		/* 2. 发出读命令00h */
		nand_cmd(0x00);

		/* 3. 发出地址(分5步发出) */
		nand_addr(addr);

		/* 4. 发出读命令30h */
		nand_cmd(0x30);

		/* 5. 判断状态 */
		nand_wait_ready();

		/* 6. 读数据 */
		for (; (col < 2048) && (i < len); col++)
		{ 
   
			buf[i] = nand_data();
			i++;
			addr++;
		}
		
		col = 0;
	}

	/* 7. 取消选中 */		
	nand_deselect();
}

3.修改start.s重定位部分

  修改arch/arm/cpu/arm920t/start.S,更改重定位代码。由于nand启动时,2440未初始化之前只有前4K可读写,所以将重定位代码放在start.S的cpu_init_crit(初始化SDRAM)段后面。修改后代码如下

#ifndef CONFIG_SKIP_LOWLEVEL_INIT
	bl	cpu_init_crit
#endif

	ldr	sp, =(CONFIG_SYS_INIT_SP_ADDR) //等于0x30000f80
	bic sp, sp, #7 /* 8-byte alignment for ABI compliance */
	
	bl nand_init_ll
	mov r0, #0       //r0->src
	//ldr r1, =_start
	ldr r1,_TEXT_BASE     //链接地址 _TEXT_BASE : 0x33f80000 0x34000000-0x33f80000=512k uboot 512k足以
	ldr r2,_bss_start_ofs		// _bss_start_ofs: __bss_start - _start (有效代码大小)

	bl copy_code_to_sdram
	bl clear_bss                         //清除bss段(参考自制uboot章节)
	ldr pc,=call_board_init_f            //绝对跳转,跳到SDRAM上执行


/* Set stackpointer in internal RAM to call board_init_f */
call_board_init_f:
	ldr	r0,=0x00000000
	bl	board_init_f

  上面的_TEXT_BASE,在start.S靠前处定义:

  由于它位于靠前处,保证了_TEXT_BASE存在前4k空间里,若直接使用ldr r1,=CONFIG_SYS_TEXT_BASE,编译器可能会将这个宏定义放在SDRAM上,则会出错。
  重定位写在前面了,所以我们还要删除start.S后面的u-boot-2012.04.01\arch\arm\lib\board.c中的 relocate_code重定位段,清除BSS段。同时在relocate_code(addr_sp, id, addr);后面增加return (unsigned int) id;，修改函数为unsigned int board_init_f(ulong bootflag)。

  同时注释掉board.c中如下的内容，固定addr的值。

  删除start.s中原有的重定位代码，删除部分如下

/* * void relocate_code (addr_sp, gd, addr_moni) * * This "function" does not return, instead it continues in RAM * after relocating the monitor code. * */
	.globl	relocate_code
relocate_code:
	mov	r4, r0	/* save addr_sp */
	mov	r5, r1	/* save addr of gd */
	mov	r6, r2	/* save addr of destination */

	/* Set up the stack */
stack_setup:
	mov	sp, r4

	adr	r0, _start
	cmp	r0, r6
	beq	clear_bss		/* skip relocation */
	mov	r1, r6			/* r1 <- scratch for copy_loop */
	ldr	r3, _bss_start_ofs
	add	r2, r0, r3		/* r2 <- source end address */

copy_loop:
	ldmia	r0!, { 
   r9-r10}		/* copy from source address [r0] */
	stmia	r1!, { 
   r9-r10}		/* copy to target address [r1] */
	cmp	r0, r2			/* until source end address [r2] */
	blo	copy_loop

#ifndef CONFIG_SPL_BUILD
	/* * fix .rel.dyn relocations */
	ldr	r0, _TEXT_BASE		/* r0 <- Text base */
	sub	r9, r6, r0		/* r9 <- relocation offset */
	ldr	r10, _dynsym_start_ofs	/* r10 <- sym table ofs */
	add	r10, r10, r0		/* r10 <- sym table in FLASH */
	ldr	r2, _rel_dyn_start_ofs	/* r2 <- rel dyn start ofs */
	add	r2, r2, r0		/* r2 <- rel dyn start in FLASH */
	ldr	r3, _rel_dyn_end_ofs	/* r3 <- rel dyn end ofs */
	add	r3, r3, r0		/* r3 <- rel dyn end in FLASH */
fixloop:
	ldr	r0, [r2]		/* r0 <- location to fix up, IN FLASH! */
	add	r0, r0, r9		/* r0 <- location to fix up in RAM */
	ldr	r1, [r2, #4]
	and	r7, r1, #0xff
	cmp	r7, #23			/* relative fixup? */
	beq	fixrel
	cmp	r7, #2			/* absolute fixup? */
	beq	fixabs
	/* ignore unknown type of fixup */
	b	fixnext
fixabs:
	/* absolute fix: set location to (offset) symbol value */
	mov	r1, r1, LSR #4		/* r1 <- symbol index in .dynsym */
	add	r1, r10, r1		/* r1 <- address of symbol in table */
	ldr	r1, [r1, #4]		/* r1 <- symbol value */
	add	r1, r1, r9		/* r1 <- relocated sym addr */
	b	fixnext
fixrel:
	/* relative fix: increase location by offset */
	ldr	r1, [r0]
	add	r1, r1, r9
fixnext:
	str	r1, [r0]
	add	r2, r2, #8		/* each rel.dyn entry is 8 bytes */
	cmp	r2, r3
	blo	fixloop
#endif

clear_bss:
#ifndef CONFIG_SPL_BUILD
	ldr	r0, _bss_start_ofs
	ldr	r1, _bss_end_ofs
	mov	r4, r6			/* reloc addr */
	add	r0, r0, r4
	add	r1, r1, r4
	mov	r2, #0x00000000		/* clear */

clbss_l:str	r2, [r0]		/* clear loop... */
	add	r0, r0, #4
	cmp	r0, r1
	bne	clbss_l

	bl coloured_LED_init
	bl red_led_on
#endif

  start.s增加第二阶段启动代码

call_board_init_f:

	ldr	r0,=0x00000000
	bl	board_init_f

	/*unsigned int id 的值存在r0中，正好给board_init_r使用*/
	ldr r1, =_TEXT_BASE
	/*调用第二阶段代码*/
	bl	board_init_r

4.修改链接脚本

  把start.S, init.c(实现重定位), lowlevel.S(实现初始化SDRAM)等文件放在最前面

rm u-boot.lds
vi arch/arm/cpu/u-boot.lds

  添加以下字段:

 . = ALIGN(4);

    .text :

    { 
   

            __image_copy_start = .;

            CPUDIR/start.o (.text)              //CPUDIR为arch/arm/cpu/arm920t目录

            board/samsung/smdk2440/libsmdk2440.o (.text)  

            *(.text)

    }

  libsmdk2440.o是将smdk2440单板目录下的所有*.c,*S文件编译后,连接成一个库文件.

5.报错修改

  报错

board.c:259: error: conflicting types for 'board_init_f'
/work/system/u-boot-2012.04.01/include/common.h:276: error: previous declaration of 'board_init_f' was here
/work/system/u-boot-2012.04.01/config.mk:312: recipe for target 'board.o' failed

  根据指示修改u-boot-2012.04.01/include/common.h 276行如下


  报错

board/samsung/smdk2440/libsmdk2440.o: In function `clear_bss':
/work/system/u-boot-2012.04.01/board/samsung/smdk2440/init.c:77: undefined reference to `__bss_end_'
Makefile:472: recipe for target 'u-boot' failed

  根据指示修改u-boot-2012.04.01/board/samsung/smdk2440/init.c:77行如下

6.重新修改链接地址

  我们指定了 CONFIG_SYS_TEXT_BASE 0x33f80000 ，所以我们的uboot不能超过512k，0x33f80000这个是不包括bss段的全局变量的。查看start.s文件。

  在反汇编中搜索_bss_end_ofs，00094b40为整个代码段的大小（包括了bss段），转换为10进制609088，已经大于了512k，所以‬重新修改CONFIG_SYS_TEXT_BASE 0x33f00000 。预留uboot空间为0x34000000-0x33f00000=1M

  然后通过旧的uboot,将新的uboot烧写到nand中

usb 1 30000000                             //先下载到SDRAM上
nand erase 0  0x80000                      //擦除512kb,必须大于新的uboot
nand write 30000000   0  0x80000           //将SDRAM上的新uboot写入nand

查看u-boot.lds

  烧写后,如下图所示:

  nand启动便实现完成了,上面的Flash: *** failed *** 是属于uboot第二阶段函数board_init_r()里的代码,表示不支持nor flash,不能实现读,写,擦除等命令。
  下一节S3C2440移植uboot之支持NORFLASH我们将移植uboot支持我们的s3c2440。