7.1 创建nand_read.c
【注意】
本程序只能用于读取2K/页的Nand。本人的Micro2440上的Nand Flash为256M，型号为K9F2G08
?
[408@WZC u-boot-2011.06]$ touch board/samsung/micro2440/nand_read.c
[408@WZC u-boot-2011.06]$ cat> board/samsung/micro2440/nand_read.c
?
#define?rNFCONF??(*(volatile unsigned *)0x4E000000)
#define?rNFCONT??(*(volatile unsigned *)0x4E000004)
#define?rNFCMD??(*(volatile unsigned *)0x4E000008)
#define?rNFADDR??(*(volatile unsigned *)0x4E00000C)
#define rNFDATA8?(*(volatile unsigned char*)0x4E000010)
#define?rNFSTAT??(*(volatile unsigned *)0x4E000020)
#define CMD_READ1???0x00????????????/* 页读命令周期1?*/
#define CMD_READ2???0x30????????????/* 页读命令周期2?*/
#define CMD_RESET???0xFF??????????/* 复位????*/
#define NF_CMD(cmd)???{rNFCMD=(cmd);}?????/* 写命令???*/
#define NF_ADDR(addr)??{rNFADDR=(addr);}????/* 写地址???*/
#define NF_RDDATA8()??(rNFDATA8)?????????/* 读8位数据??*/
#define NF_nFCE_L()???{rNFCONT&=~(1<<1);}????/* 片选使能???*/
#define NF_nFCE_H()???{rNFCONT|=(1<<1);}????/* 片选禁用???*/
#define NF_WAITRB()??? ??{while(!(rNFSTAT&(1<<1)));}??/* 等待就绪???*/
#define NF_CLEAR_RB()??? ?{rNFSTAT |= (1<<2);}???/* 清除就绪/忙位?*/
#define NF_DETECT_RB()??? ?{while(!(rNFSTAT&(1<<2)));}??/* 等待就绪???*/
#define TACLS??1
#define TWRPH0??2
#define TWRPH1??1
void delay(int i)
{
?while(i-->0);
}
void Nand_Init(void)
{
?rNFCONF = (TACLS<<12)|(TWRPH0<<8)|(TWRPH1<<4)|(0<<0);?
?rNFCONT = (1<<4)|(1<<1)|(1<<0);
}
static void Nand_Reset(void)
{
?NF_nFCE_L();??????/* 片选使能 ??*/
?NF_CLEAR_RB();??????/* 清除就绪/忙位 ?*/
?NF_CMD(CMD_RESET);?????/* 写复位命令??*/
?NF_DETECT_RB();??????/* 等待就绪???*/
?NF_nFCE_H();??????/* 片选禁用???*/
}
unsigned char Nand_ReadPage(const int page,unsigned char * const buffer)
{
?int i;
?
?Nand_Reset();
?
?NF_nFCE_L();
?NF_CLEAR_RB();
?NF_CMD(CMD_READ1);?
?NF_ADDR(0x0);
?NF_ADDR(0x0);
?NF_ADDR(page&0xff);
?NF_ADDR((page>>8)&0xff);
?NF_ADDR((page>>16)&0xff);
?NF_CMD(CMD_READ2);?
???
?NF_DETECT_RB();
?for (i = 0; i < 2048; i++)?
?{
??buffer[i] =? NF_RDDATA8();
?}
?
?NF_nFCE_H();
}
int nand_read(int start_page,int read_pages,unsigned char *buffer)
{
?int i;
?Nand_Init();
?for(i=0; i<read_pages; i++)
?{
??Nand_ReadPage(start_page,buffer + 2048*i);
??start_page++;
?}
?return 0;
}
?
7.2 board/samsung/micro2440/Makefile
COBJS := micro2440.o flash.o?nand_read.o
7.3 arch/arm/cpu/arm920t/u-boot.lds
?.text :
?{
??arch/arm/cpu/arm920t/start.o?(.text)
??board/samsung/micro2440/libmicro2440.o??? (.text)
??*(.text)
?}
【说明】
如果是在RAM中运行，一定要删去board/samsung/micro2440/libmicro2440.o??? (.text)，否则在RAM中也不能运行。原因尚不理解，需要阅读代码。
7.4 arch/arm/cpu/arm920t/start.S
下面红色部分是添加的部分，黑色的代码用于定位。
#ifndef CONFIG_SKIP_LOWLEVEL_INIT
??? bl cpu_init_crit
#endif
#ifdef CONFIG_S3C2440_NAND_BOOT?
??? ldr sp,=0x30008000?
??? ldr r0,=0x0;?
??? ldr r1,_end_ofs?
??? mov r1,r1,LSR #11?
??? add r1,#1?
??? ldr r2,=(CONFIG_SYS_TEXT_BASE)?
??? bl nand_read?
??? ldr pc,=relocations?
#endif
......
......
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?
#ifdef CONFIG_S3C2440_NAND_BOOT?
relocations:?
??? ldr r6,=CONFIG_SYS_TEXT_BASE?
#endif?
#ifndef CONFIG_PRELOADER?
/*?
* fix .rel.dyn relocations?
*/
......
......
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?
7.5 include/configs/micro2440.h
#define CONFIG_S3C2440_NAND_BOOT
/* #define CONFIG_SKIP_LOWLEVEL_INIT */
【说明】
由于要在Nand Flash中运行，所以需要注释掉#define CONFIG_SKIP_LOWLEVEL_INIT
7.6 arch/arm/lib/board.c
void board_init_f (ulong bootflag)?
{?
??? ......?
??? gd->mon_len = _bss_end_ofs?+ 0x100000; /* why */?
??? ......?
这里的修改参考了bscbem的日志：http://my.chinaunix.net/space.php?uid=24319701&do=blog&id=136249
如果有读者想了解原理请参考这个日志。
?
??? /* relocate_code (addr_sp,id,addr); */
#ifdef CONFIG_S3C2440_NAND_BOOT /*add by wzc*/
??? __asm__ __volatile__("mov sp,%0"::"r"(addr_sp):"sp");/*add by wzc*/?
??? board_init_r(id,addr);
#else
??? relocate_code (addr_sp,addr);
??? /* NOTREACHED - relocate_code() does not return */
#endif
}【说明】
至于gd->mon_len = _bss_end_ofs + 0x100000;我也不理解，需要阅读源代码才能解释。
7.7 下载到Nand Flash
?到这里应该就可以从Nand Flash启动了。
