TX2440 ARM开发板Uboot移植（二、让u-boot从nandFlash动起来）

接上：让u-boot从norFlash动起来

完成上面工作后，u-boot中还没有对2440上Nand Flash的支持，以及u-boot从Nand Flash上启动，这些得我们一步步去实现了。

1、修改配置文件 include/configs/smdk2440.h ：

1.1、新增宏 CONFIG_CMD_NAND (大概在95行)
#define CONFIG_CMD_CACHE
#define CONFIG_CMD_DATE
#define CONFIG_CMD_ELF
#define CONFIG_CMD_NAND
#define CONFIG_CMD_ENV

1.2、在文件的最后面增加3个宏:

//NAND flash settings
#define?NAND_CTL_BASE???? 0x4E000000? //NAND Flash的地址
#define CFG_MAX_NAND_DEVICE? 1?????????//NAND Flash设备数目为1
#define NAND_MAX_CHIPS? ??? 1?? ??? ???????? ?//每个NAND设备由1个NADN芯片组成

2、? 修改 include/s3c24x0.h 文件，增加S3C2440_NAND数据结构（168行）

/* NAND FLASH (see S3C2440 manual chapter 6) */
typedef struct {
??? S3C24X0_REG32 NFCONF;
??? S3C24X0_REG32 NFCONT;
??? S3C24X0_REG32 NFCMD;
??? S3C24X0_REG32 NFADDR;
??? S3C24X0_REG32 NFDATA;
??? S3C24X0_REG32 NFMECCD0;
??? S3C24X0_REG32 NFMECCD1;
??? S3C24X0_REG32 NFSECCD;
??? S3C24X0_REG32 NFSTAT;
??? S3C24X0_REG32 NFESTAT0;
??? S3C24X0_REG32 NFESTAT1;
??? S3C24X0_REG32 NFMECC0;
??? S3C24X0_REG32 NFMECC1;
??? S3C24X0_REG32 NFSECC;
??? S3C24X0_REG32 NFSBLK;
??? S3C24X0_REG32 NFEBLK;
} /*__attribute__((__packed__))*/ S3C2440_NAND;

3、u-boot默认是从Nor Flash启动的。修改文件 cpu/arm920t/start.S ，使u-boot可以从Nand Flash启动：

对文件改动较大，仔细对比源代码，主要的修改是将栈的初始化放到前面，用于后面调用C函数的需要；
判断u-boot不是从内存启动后，调用CopyCode2Ram函数，实现把启动代码拷贝到内存
/*
? * we do sys-critical inits only at reboot,
? * not when booting from ram!
? */
#ifndef CONFIG_SKIP_LOWLEVEL_INIT
?adr?r0,_start????/* r0 <- current position of code?? */
?ldr?r1,_TEXT_BASE??/* test if we run from flash or RAM */
?cmp???? r0,r1??????? /* don't reloc during debug???????? */
?blne?cpu_init_crit
#endif

stack_setup:??????//将栈的初始化放到前面
?ldr?r0,_TEXT_BASE?????/* upper 128 KiB: relocated uboot?? */
?sub?r0,r0,#CFG_MALLOC_LEN??/* malloc area? ???????????????? */
?sub?r0,#CFG_GBL_DATA_SIZE ?/* bdinfo??????????????*/
#ifdef CONFIG_USE_IRQ
?sub?r0,#(CONFIG_STACKSIZE_IRQ+CONFIG_STACKSIZE_FIQ)
#endif
?sub?sp,#12??/* leave 3 words for abort-stack??? */

relocate:??????/* relocate U-Boot to RAM???? */
?adr?r0,_start??/* r0 <- current position of code?? */
?ldr?r1,r1????????????????? /* don't reloc during debug???????? */
?beq???? clear_bss

?ldr?r2,_armboot_start
?ldr?r3,_bss_start
?sub?r2,r3,r2??/* r2 <- size of armboot??????????? */
?bl CopyCode2Ram???// 调用board/smdk2440/boot_Init.c里的CopyCode2Ram函数，把启动代码拷贝到内存

clear_bss:
?ldr?r0,_bss_start??/* find start of bss segment??????? */
?ldr?r1,_bss_end??/* stop here??????????????????????? */
?mov?r2,#0x00000000??/* clear??????????????????????????? */
clbss_l:str?r2,[r0]??/* clear loop...??????????????????? */
?add?r0,#4
?cmp?r0,r1
?ble?clbss_l

?ldr?pc,_start_armboot

_start_armboot:?.word start_armboot

4、新建 board/smdk2440/boot_Init.c 文件，实现从NandFlsh读取字节；判断启动方式，并拷贝启动代码到内存。代码如下：

#include <common.h> #include <s3c2440.h> #define BUSY??????????? 1 #ifdef?NAND_LARGEPAGE #define NAND_SECTOR_SIZE 2048 #else #define NAND_SECTOR_SIZE 512 #endif #define NAND_BLOCK_MASK (NAND_SECTOR_SIZE - 1) /* 供外部调用的函数 */ void nand_init_ll(void); void nand_read_ll(unsigned char *buf,unsigned long start_addr,int size); /* S3C2440的NAND Flash处理函数 */ static void nand_reset(void); static void wait_idle(void); static void nand_select_chip(void); static void nand_deselect_chip(void); static void write_cmd(int cmd); static void write_addr(unsigned int addr); static unsigned char read_data(void); /* S3C2440的NAND Flash操作函数 */ /* 复位 */ static void nand_reset(void) { ??? nand_select_chip(); ??? write_cmd(0xff);? // 复位命令 ??? wait_idle(); ??? nand_deselect_chip(); } /* 等待NAND Flash就绪 */ static void wait_idle(void) { ? int i; ?S3C2440_NAND * s3c2440nand = (S3C2440_NAND *)0x4e000000; ?volatile unsigned char *p = (volatile unsigned char *)&s3c2440nand->NFSTAT; ?while(!(*p & BUSY)) ?for(i=0; i<10; i++); } /* 发出片选信号 */ static void nand_select_chip(void) { ?int i; ?S3C2440_NAND * s3c2440nand = (S3C2440_NAND *)0x4e000000; ?s3c2440nand->NFCONT &= ~(1<<1); ?for(i=0; i<10; i++);???? } /* 取消片选信号 */ static void nand_deselect_chip(void) { ?S3C2440_NAND * s3c2440nand = (S3C2440_NAND *)0x4e000000; ??? s3c2440nand->NFCONT |= (1<<1); } /* 发出命令 */ static void write_cmd(int cmd) { ?S3C2440_NAND * s3c2440nand = (S3C2440_NAND *)0x4e000000; ??? volatile unsigned char *p = (volatile unsigned char *)&s3c2440nand->NFCMD; ??? *p = cmd; } /* 发出地址 Nand进行寻址的部分*/ static void write_addr(unsigned int addr) { ? int i; ?S3C2440_NAND * s3c2440nand = (S3C2440_NAND *)0x4e000000; ?volatile unsigned char *p = (volatile unsigned char *)&s3c2440nand->NFADDR; #ifndef?NAND_LARGEPAGE???? ?*p = addr & 0xff; ?for(i=0; i<10; i++); ?*p = (addr >> 9) & 0xff; ?for(i=0; i<10; i++); ?*p = (addr >> 17) & 0xff; ?for(i=0; i<10; i++); ?*p = (addr >> 25) & 0xff; ?for(i=0; i<10; i++); #else ?int col,page; ?col = addr & NAND_BLOCK_MASK; ?page = addr / NAND_SECTOR_SIZE; ?*p = col & 0xff;???/* Column Address A0~A7 */ ?for(i=0; i<10; i++);?? ?*p = (col >> 8) & 0x0f;??/* Column Address A8~A11 */ ?for(i=0; i<10; i++); ?*p = page & 0xff;???/* Row Address A12~A19 */ ?for(i=0; i<10; i++); ?*p = (page >> 8) & 0xff;?/* Row Address A20~A27 */ ?for(i=0; i<10; i++); ?*p = (page >> 16) & 0x03;?/* Row Address A28~A29 */ ?for(i=0; i<10; i++); #endif } /* 读取数据 */ static unsigned char read_data(void) { ?S3C2440_NAND * s3c2440nand = (S3C2440_NAND *)0x4e000000; ?volatile unsigned char *p = (volatile unsigned char *)&s3c2440nand->NFDATA; ?return *p; } /* 初始化NAND Flash */ void nand_init_ll(void) { ?S3C2440_NAND * s3c2440nand = (S3C2440_NAND *)0x4e000000; #define TACLS?? 0 #define TWRPH0? 3 #define TWRPH1? 0 ?/* 设置时序 */ ?s3c2440nand->NFCONF = (TACLS<<12)|(TWRPH0<<8)|(TWRPH1<<4); ?/* 使能NAND Flash控制器,初始化ECC,禁止片选 */ ?s3c2440nand->NFCONT = (1<<4)|(1<<1)|(1<<0); ?/* 复位NAND Flash */ ?nand_reset(); } /* 读函数 */ void nand_read_ll(unsigned char *buf,int size) { ??? int i,j; ??? if ((start_addr & NAND_BLOCK_MASK) || (size & NAND_BLOCK_MASK)) { ??????? return ;????/* 地址或长度不对齐 */ ??? } ????/* 选中芯片 */ ??? nand_select_chip(); ??? for(i=start_addr; i < (start_addr + size);) { ??????/* 发出READ0命令 */ ????? write_cmd(0); ??????/* Write Address */ ????? write_addr(i); #ifdef NAND_LARGEPAGE ?write_cmd(0x30); #endif ????? wait_idle(); ????? for(j=0; j < NAND_SECTOR_SIZE; j++,i++) { ????????? *buf = read_data(); ????????? buf++; ????? } ??? } ????/* 取消片选信号 */ ??? nand_deselect_chip(); ??? return ; } int bBootFrmNORFlash(void)???/* 取OM0、1的值，判断开发板是从NorFlash还是NandFlash启动 */ { ??volatile unsigned int *bwsCON = (volatile unsigned int *)0x48000000; ??unsigned int bwsVal; ??bwsVal = *bwsCON; ??bwsVal &= 0x06; ??if (bwsVal==0){ ???return 0; ??} ??else?{ ???return 1; ??} } int CopyCode2Ram(unsigned long start_addr,unsigned char *buf,int size) { ??? unsigned int *pdwDest; ??? unsigned int *pdwSrc; ??? int i; ??? if (bBootFrmNORFlash()) ??? { ????? pdwDest = (unsigned int *)buf; ????? pdwSrc? = (unsigned int *)start_addr; ????? /* 从 NOR Flash启动 */ ????? for (i = 0; i < size / 4; i++) ????? { ??????? pdwDest[i] = pdwSrc[i]; ????? } ??? } ??? else ??? { ????? /* 初始化NAND Flash */ ???nand_init_ll(); ????? /* 从 NAND Flash启动 */ ????? nand_read_ll(buf,start_addr,(size + NAND_BLOCK_MASK)&~(NAND_BLOCK_MASK)); ??? } ?return 0; }

注意：上面这段代码中对Nand进行寻址的部分，这跟具体的Nand Flash的寻址方式有关。根据开发板上的Nand Flash(K9F1208U0C)数据手册得知，片内寻址是采用26位地址形式。从第0位开始分四次通过I/O0－I/O7进行传送，并进行片内寻址。具体含义和结构图如下(相关概念参考Nand数据手册)：

5、在 board/smdk2440/Makefile 中添加 boot_Init.c 的编译选项，使他编译到u-boot中：

COBJS????:= my2440.o flash.o?boot_Init.o

6、还有一个重要的地方要修改，在 cpu/arm920t/u-boot.lds 中，这个u-boot启动连接脚本文件决定了u-boot运行的入口地址，以及各个段的存储位置，这也是链接定位的作用。添加下面两行代码，主要目的是防止编译器把CopyCode2Ram的子函数放到4K之后，否则是无法启动的。如下：

.text :
{
????? cpu/arm920t/start.o??? (.text)
??????board/smdk2440/boot_Init.o (.text) ????? board/smdk2440/lowlevel_init.o (.text)???? ????? *(.text) }