本文实现U-Boot的写操作，具体步骤如下：
1. 加入 NAND 闪存芯片型号
在/include/linux/mtd/ nand_ids.h 中对如下结构体赋值进行修改:
static struct nand_flash_dev nand_flash_ids[]= {
......
{"Samsung K9F1208U0M", NAND_MFR_SAMSUNG, 0x76, 26, 0, 3, 0x4000, 0},
......
}
这样对于该款 NAND 闪存芯片的操作才能正确执行。
2. 编写 NAND 闪存初始化函数
在/drivers/nand_legacy/nand_legacy.c 中加入 nand_init()函数。
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#if (CONFIG_COMMANDS & CFG_CMD_NAND)
#include <s3c2410.h>
typedef enum {
NFCE_LOW,
NFCE_HIGH
} NFCE_STATE;
static inline void NF_Conf(u16 conf)
{
S3C2410_NAND * const nand = S3C2410_GetBase_NAND();
nand->NFCONF = conf;
}
static inline void NF_Cmd(u8 cmd)
{
S3C2410_NAND * const nand = S3C2410_GetBase_NAND();
nand->NFCMD = cmd;
}
static inline void NF_CmdW(u8 cmd)
{
NF_Cmd(cmd);
udelay(1);
}
static inline void NF_Addr(u8 addr)
{
S3C2410_NAND * const nand = S3C2410_GetBase_NAND();
nand->NFADDR = addr;
}
static inline void NF_SetCE(NFCE_STATE s)
{
S3C2410_NAND * const nand = S3C2410_GetBase_NAND();
switch (s) {
case NFCE_LOW:
nand->NFCONF &= ~(1<<11);
break;
case NFCE_HIGH:
nand->NFCONF |= (1<<11);
break;
}
}
static inline void NF_WaitRB(void)
{
S3C2410_NAND * const nand = S3C2410_GetBase_NAND();
while (!(nand->NFSTAT & (1<<0)));
}
static inline void NF_Write(u8 data)
{
S3C2410_NAND * const nand = S3C2410_GetBase_NAND();
nand->NFDATA = data;
}
static inline u8 NF_Read(void)
{
S3C2410_NAND * const nand = S3C2410_GetBase_NAND();
return(nand->NFDATA);
}
static inline void NF_Init_ECC(void)
{
S3C2410_NAND * const nand = S3C2410_GetBase_NAND();
nand->NFCONF |= (1<<12);
}
static inline u32 NF_Read_ECC(void)
{
S3C2410_NAND * const nand = S3C2410_GetBase_NAND();
return(nand->NFECC);
}
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 0 /* a little bit too optimistic */
#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)
{
S3C2410_NAND * const nand = S3C2410_GetBase_NAND();
NF_Init();
#ifdef DEBUG
printf("NAND flash probing at 0x%.8lX\n", (ulong)nand);
#endif
printf ("%4lu MB\n", nand_probe((ulong)nand) >> 20);
}
#endif /* CONFIG_COMMANDS & CFG_CMD_NAND */
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可以看到 nand_init()调用 NF_Init()函数,使能 nand flash 控制器和 nand flash;调用 NF_Reset()函数置位,NF_WaitRB()查询 nand flash 的状态,最后在调用 nand_probe((ulong)nand)函数探测 nand flash.
3. 修改include/configs/GEC2410.h，在上次修改的基础上加上如下代码，定义 NAND 闪存命令层的底
接口函数等：
#define CFG_NAND_LEGACY 1
//#define NFCE_LOW 0
//#define NFCE_HIGH 1
#define CFG_ENV_IS_IN_NAND 1
#define CFG_NAND_BASE 0x4E000000
#define CMD_SAVEENV
#define CFG_ENV_SIZE 0x10000 /* Total Size of Environment Sector */
#define CFG_ENV_OFFSET 0x20000 /*环境变量在NAND FLASH的0x20000处*/
#define CFG_MONITOR_BASE PHYS_SDRAM_1
/*-----------------------------------------------------------------------
* NAND flash settings
*/
#if (CONFIG_COMMANDS & CFG_CMD_NAND)
#define CFG_NAND_LEGACY
#define CFG_MAX_NAND_DEVICE 1 /* Max number of NAND devices */
#define SECTORSIZE 512
#define ADDR_COLUMN 1
#define ADDR_PAGE 2
#define ADDR_COLUMN_PAGE 3
#define NAND_ChipID_UNKNOWN 0x00
#define NAND_MAX_FLOORS 1
#define NAND_MAX_CHIPS 1
#define NAND_WAIT_READY(nand) NF_WaitRB()
#define NAND_DISABLE_CE(nand) NF_SetCE(NFCE_HIGH)
#define NAND_ENABLE_CE(nand) NF_SetCE(NFCE_LOW)
#define WRITE_NAND_COMMAND(d, adr) NF_Cmd(d)
#define WRITE_NAND_COMMANDW(d, adr) NF_CmdW(d)
#define WRITE_NAND_ADDRESS(d, adr) NF_Addr(d)
#define WRITE_NAND(d, adr) NF_Write(d)
#define READ_NAND(adr) NF_Read()
/* the following functions are NOP's because S3C24X0 handles this in hardware */
#define NAND_CTL_CLRALE(nandptr)
#define NAND_CTL_SETALE(nandptr)
#define NAND_CTL_CLRCLE(nandptr)
#define NAND_CTL_SETCLE(nandptr)
#define CONFIG_MTD_NAND_VERIFY_WRITE 1
#define CONFIG_MTD_NAND_ECC_JFFS2 1
#endif /* CONFIG_COMMANDS & CFG_CMD_NAND */
4. 在GEC2410.h中打开命令：
/***********************************************************
* Command definition
***********************************************************/
#define CONFIG_COMMANDS \
(CONFIG_CMD_DFL | \
CFG_CMD_CACHE | \
CFG_CMD_ENV | \
CFG_CMD_NET | \
CFG_CMD_PING | \
CFG_CMD_NAND | \ /* 打开 nand flash 命令 */
/*CFG_CMD_EEPROM |*/ \
/*CFG_CMD_I2C |*/ \
/*CFG_CMD_USB |*/ \
CFG_CMD_REGINFO | \
CFG_CMD_DATE | \
CFG_CMD_ELF)
好了，make一下，看看结果，很不幸运，/env_nand.c：206 undefined reference to 'nand_info'等等问题，原来nand flash 真正的擦除和读写函数使用的是 drivers/nand_legacy/ 目录下面的读写、擦除函数
int nand_legacy_erase(struct nand_chip* nand, size_t ofs,size_t len, int clean);
int nand_legacy_rw(struct nand_chip* nand, int cmd,size_t start, size_t len,size_t * retlen, u_char * buf);
5. 修改saveenv中对nand的读写函数为nand_legacy的读写函数，修改common/env_nand.c如下：
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#include <common.h>
#if defined(CFG_ENV_IS_IN_NAND) /* Environment is in Nand Flash */
#include <command.h>
#include <environment.h>
#include <linux/stddef.h>
#include <malloc.h>
#include <nand.h>
#if ((CONFIG_COMMANDS&(CFG_CMD_ENV|CFG_CMD_NAND)) == (CFG_CMD_ENV|CFG_CMD_NAND))
#define CMD_SAVEENV
#elif defined(CFG_ENV_OFFSET_REDUND)
#error Cannot use CFG_ENV_OFFSET_REDUND without CFG_CMD_ENV & CFG_CMD_NAND
#endif
#if defined(CFG_ENV_SIZE_REDUND) && (CFG_ENV_SIZE_REDUND != CFG_ENV_SIZE)
#error CFG_ENV_SIZE_REDUND should be the same as CFG_ENV_SIZE
#endif
#ifdef CONFIG_INFERNO
#error CONFIG_INFERNO not supported yet
#endif
/* My Add*/
int nand_legacy_erase(struct nand_chip* nand,
size_t ofs, size_t len, int clean);
int nand_legacy_rw (struct nand_chip* nand, int cmd,
size_t start, size_t len,
size_t * retlen, u_char * buf);
/* My Add*/
extern struct nand_chip nand_dev_desc[CFG_MAX_NAND_DEVICE];
/* info for NAND chips, defined in drivers/nand/nand.c */
//extern nand_info_t nand_info[];
nand_info_t nand_info[CFG_MAX_NAND_DEVICE];
/* references to names in env_common.c */
extern uchar default_environment[];
extern int default_environment_size;
......
......
#else /* ! CFG_ENV_OFFSET_REDUND */
int saveenv(void) /* 2008-6-26 by weij */
{
ulong total;
int ret = 0;
puts ("Erasing Nand...");
//if (nand_erase(&nand_info[0], CFG_ENV_OFFSET, CFG_ENV_SIZE))
if (nand_legacy_erase(nand_dev_desc+0, CFG_ENV_OFFSET, CFG_ENV_SIZE, 0))
return 1;
puts ("Writing to Nand... ");
total = CFG_ENV_SIZE;
//ret = nand_write(&nand_info[0], CFG_ENV_OFFSET, &total, (u_char*)env_ptr);
nand_legacy_rw(nand_dev_desc+0, 0x00 | 0x02, CFG_ENV_OFFSET, CFG_ENV_SIZE, &total, (u_char*)env_ptr);
if (ret || total != CFG_ENV_SIZE)
return 1;
puts ("done\n");
return ret;
}
#endif /* CFG_ENV_OFFSET_REDUND */
......
......
/*
* The legacy NAND code saved the environment in the first NAND device i.e.,
* nand_dev_desc + 0. This is also the behaviour using the new NAND code.
*/
void env_relocate_spec (void)
{
#if !defined(ENV_IS_EMBEDDED)
ulong total;
int ret;
total = CFG_ENV_SIZE;
//ret = nand_read(&nand_info[0], CFG_ENV_OFFSET, &total, (u_char*)env_ptr);
ret=nand_legacy_rw(nand_dev_desc+0, 0x01 | 0x02, CFG_ENV_OFFSET, CFG_ENV_SIZE, &total, (u_char*)env_ptr);
if (ret || total != CFG_ENV_SIZE)
return use_default();
if (crc32(0, env_ptr->data, ENV_SIZE) != env_ptr->crc)
return use_default();
#endif /* ! ENV_IS_EMBEDDED */
}
#endif /* CFG_ENV_OFFSET_REDUND */
......
......
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修改完之后，make一下，生成U-Boot.bin文件，烧写到NAND FLASH,用setenv 设置环境变量，之后再保存saveenv.用TFTP命令，下载内核，就可以出现
TFTP from server 192.168.0.50; our IP address is 192.168.0.100
Filename 'uImage'.
Load address: 0x30007fc0
Loading: #################################################################
#################################################################
#################################################################
#################################################################
####################################################
done
下一步就是编译内核、引导内核啦！
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