在u-boot-1.1.6移植(二)http://blog.chinaunix.net/u2/74310/showart.php?id=1091929中提到：u-boot 运行至第二阶段进入 start_armboot()函数。其中 nand_init()函数是对 nand flash 的最初初始化函数。其调用与 CFG_NAND_LEGACY 宏有关,如果没定义 CFG_NAND_LEGACY 这个宏,就按照start_armboot()调用 drivers/nand/nand.c 中的 nand_init 函数(该函数在 1.1.6 已经被实现), 但还有个 board_nand_init()函数没实现,需自己添加；如果定义了CFG_NAND_LEGACY,就不使用默认的 nand_init,而调用自己写的 nand_init 函数了。u-boot-1.1.6中对NAND flash的支持有新旧两套代码，新代码在drivers/nand目录下，旧代码在drivers/nand_legacy目录下，文档doc/README.nand对这两套代码有所说明：使用旧代码需要定义更多的宏，u-boot-1.1.6移植(二)中可以看到，比较复杂，而新代码移植自Linux 2.6.12，它更加智能，可以自动识别更多型号的NAND flash。本文使用新代码并移植在优龙FS2410成功。
NAND flash 的支持以及下篇《u-boot烧写yaffs文件系统映象》参考《嵌入式Linux应用开发完全手册》，实验时得到该书作者南方兄的热情帮助，在此感谢！
移植过程：
一、代码搬运
@ copy UBOOT to RAM
ldr r0, _TEXT_BASE
mov r1, #0x0
mov r2, #0x20000 //改为mov r2,#0x40000,这是FS2410分配给u-boot的存储空间
bl nand_read_ll
二、修改配置文件 include/configs/fs2410.h 使支持NAND
/***********************************************************
* Command definition
***********************************************************/
#define CONFIG_COMMANDS \
(CONFIG_CMD_DFL | \
CFG_CMD_CACHE | \
CFG_CMD_ENV | \
CFG_CMD_NET | \
CFG_CMD_PING | \
CFG_CMD_NAND | \
/*CFG_CMD_EEPROM |*/ \
/*CFG_CMD_I2C |*/ \
/*CFG_CMD_USB |*/ \
CFG_CMD_REGINFO | \
CFG_CMD_DATE | \
CFG_CMD_ELF)
#define CFG_NAND_BASE 0x4E000000
#define CFG_MAX_NAND_DEVICE 1 /* Max number of NAND devices */
#define NAND_MAX_CHIPS 1
/*保存环境变量用到的宏，否则不能 saveenv */
#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 0x30000 /*环境变量在NAND FLASH的0x30000处*/
/*修改默认配置参数以方便使用*/
#define CONFIG_BOOTDELAY 3
#define CONFIG_BOOTARGS "noinitrd root=/dev/mtdblock2 init=/linuxrc devfs=mount console=ttySAC0,115200"
#define CONFIG_ETHADDR 08:00:3e:26:0a:5b
#define CONFIG_NETMASK 255.255.255.0
#define CONFIG_IPADDR 192.168.1.100
#define CONFIG_SERVERIP 192.168.1.2
/*#define CONFIG_BOOTFILE "elinos-lart" */
#define CONFIG_BOOTCOMMAND "nand read 0x30007fc0 0x40000 0x1c0000; bootm 0x30007fc0"
三、建立cpu/arm920t/s3c24x0/nand_flash.c，实现board_nand_init函数
《嵌入式Linux应用开发完全手册》中介召的nand_flash.c包含对S3C2440的支持，在这里一并列出，供日后参考。
(1)针对S3C2410、S3C2440 NAND Flash控制器的不同来定义一些数据结构和函数，在include/s3c24x0.h 文件中增加S3C2440_NAND数据结构。
/* 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;
(2)在 include/s3c2410.h 文件中仿照 S3C2410_GetBase_NAND函数定义S3C2440_GetBase_NAND函数。
/* for s3c2440, */
static inline S3C2440_NAND * const S3C2440_GetBase_NAND(void)
{
return (S3C2440_NAND * const)S3C2410_NAND_BASE;
}
(3) cpu/arm920t/s3c24x0/nand_flash.c
/*
* Nand flash interface of s3c2410/s3c2440, by
* Changed from drivers/mtd/nand/s3c2410.c of kernel 2.6.13
*/
#include
#if (CONFIG_COMMANDS & CFG_CMD_NAND) && !defined(CFG_NAND_LEGACY)
#include
#include
DECLARE_GLOBAL_DATA_PTR;
#define S3C2410_NFSTAT_READY (1<<0)
#define S3C2410_NFCONF_nFCE (1<<11)
#define S3C2440_NFSTAT_READY (1<<0)
#define S3C2440_NFCONT_nFCE (1<<1)
/* select chip, for s3c2410 */
static void s3c2410_nand_select_chip(struct mtd_info *mtd, int chip)
{
S3C2410_NAND * const s3c2410nand = S3C2410_GetBase_NAND();
if (chip == -1) {
s3c2410nand->NFCONF |= S3C2410_NFCONF_nFCE;
} else {
s3c2410nand->NFCONF &= ~S3C2410_NFCONF_nFCE;
}
}
/* command and control functions, for s3c2410
*
* Note, these all use tglx's method of changing the IO_ADDR_W field
* to make the code simpler, and use the nand layer's code to issue the
* command and address sequences via the proper IO ports.
*
*/
static void s3c2410_nand_hwcontrol(struct mtd_info *mtd, int cmd)
{
S3C2410_NAND * const s3c2410nand = S3C2410_GetBase_NAND();
struct nand_chip *chip = mtd->priv;
switch (cmd) {
case NAND_CTL_SETNCE:
case NAND_CTL_CLRNCE:
printf("%s: called for NCE\n", __FUNCTION__);
break;
case NAND_CTL_SETCLE:
chip->IO_ADDR_W = (void *)&s3c2410nand->NFCMD;
break;
case NAND_CTL_SETALE:
chip->IO_ADDR_W = (void *)&s3c2410nand->NFADDR;
break;
/* NAND_CTL_CLRCLE: */
/* NAND_CTL_CLRALE: */
default:
chip->IO_ADDR_W = (void *)&s3c2410nand->NFDATA;
break;
}
}
/* s3c2410_nand_devready()
*
* returns 0 if the nand is busy, 1 if it is ready
*/
static int s3c2410_nand_devready(struct mtd_info *mtd)
{
S3C2410_NAND * const s3c2410nand = S3C2410_GetBase_NAND();
return (s3c2410nand->NFSTAT & S3C2410_NFSTAT_READY);
}
/* select chip, for s3c2440 */
static void s3c2440_nand_select_chip(struct mtd_info *mtd, int chip)
{
S3C2440_NAND * const s3c2440nand = S3C2440_GetBase_NAND();
if (chip == -1) {
s3c2440nand->NFCONT |= S3C2440_NFCONT_nFCE;
} else {
s3c2440nand->NFCONT &= ~S3C2440_NFCONT_nFCE;
}
}
/* command and control functions */
static void s3c2440_nand_hwcontrol(struct mtd_info *mtd, int cmd)
{
S3C2440_NAND * const s3c2440nand = S3C2440_GetBase_NAND();
struct nand_chip *chip = mtd->priv;
switch (cmd) {
case NAND_CTL_SETNCE:
case NAND_CTL_CLRNCE:
printf("%s: called for NCE\n", __FUNCTION__);
break;
case NAND_CTL_SETCLE:
chip->IO_ADDR_W = (void *)&s3c2440nand->NFCMD;
break;
case NAND_CTL_SETALE:
chip->IO_ADDR_W = (void *)&s3c2440nand->NFADDR;
break;
/* NAND_CTL_CLRCLE: */
/* NAND_CTL_CLRALE: */
default:
chip->IO_ADDR_W = (void *)&s3c2440nand->NFDATA;
break;
}
}
/* s3c2440_nand_devready()
*
* returns 0 if the nand is busy, 1 if it is ready
*/
static int s3c2440_nand_devready(struct mtd_info *mtd)
{
S3C2440_NAND * const s3c2440nand = S3C2440_GetBase_NAND();
return (s3c2440nand->NFSTAT & S3C2440_NFSTAT_READY);
}
/*
* Nand flash hardware initialization:
* Set the timing, enable NAND flash controller
*/
static void s3c24x0_nand_inithw(void)
{
S3C2410_NAND * const s3c2410nand = S3C2410_GetBase_NAND();
S3C2440_NAND * const s3c2440nand = S3C2440_GetBase_NAND();
#define TACLS 0
#define TWRPH0 4
#define TWRPH1 2
if (gd->bd->bi_arch_number == MACH_TYPE_SMDK2410)
{
/* Enable NAND flash controller, Initialize ECC, enable chip select, Set flash memory timing */
s3c2410nand->NFCONF = (1<<15)|(1<<12)|(1<<11)|(TACLS<<8)|(TWRPH0<<4)|(TWRPH1<<0);
}
else
{
/* Set flash memory timing */
s3c2440nand->NFCONF = (TACLS<<12)|(TWRPH0<<8)|(TWRPH1<<4);
/* Initialize ECC, enable chip select, NAND flash controller enable */
s3c2440nand->NFCONT = (1<<4)|(0<<1)|(1<<0);
}
}
/*
* Called by drivers/nand/nand.c, initialize the interface of nand flash
*/
void board_nand_init(struct nand_chip *chip)
{
S3C2410_NAND * const s3c2410nand = S3C2410_GetBase_NAND();
S3C2440_NAND * const s3c2440nand = S3C2440_GetBase_NAND();
s3c24x0_nand_inithw();
if (gd->bd->bi_arch_number == MACH_TYPE_SMDK2410) {
chip->IO_ADDR_R = (void *)&s3c2410nand->NFDATA;
chip->IO_ADDR_W = (void *)&s3c2410nand->NFDATA;
chip->hwcontrol = s3c2410_nand_hwcontrol;
chip->dev_ready = s3c2410_nand_devready;
chip->select_chip = s3c2410_nand_select_chip;
chip->options = 0;
} else {
chip->IO_ADDR_R = (void *)&s3c2440nand->NFDATA;
chip->IO_ADDR_W = (void *)&s3c2440nand->NFDATA;
chip->hwcontrol = s3c2440_nand_hwcontrol;
chip->dev_ready = s3c2440_nand_devready;
chip->select_chip = s3c2440_nand_select_chip;
chip->options = 0;
}
chip->eccmode = NAND_ECC_SOFT;
}
#endif
四、将nand_flash.c编入 u-boot，修改cpu/arm920t/s3c24x0/Makefile文件
COBJS = i2c.o interrupts.o serial.o speed.o \
usb_ohci.o nand_flash.o
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，如图1所示，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);
至此，编译生成 u-boot.bin 并烧入NAND Flash,启动，便可以引导内核了。
