这个问题断断续续花费了几天时间才算彻底解决。用这么长时间解决这么个小问题，什么原因？分析一下，归咎与我代码阅读能力及调试能力太差。以前裁的UBOOT都是运行在nor的，而且裁了几次uboot都是照抄别人的手册，实在收获甚微。过去的惯性驱使我再次参照别人的手册修改代码，这次可没那么顺利。
在此要感谢tekkamanninja ，我是参照这个superman的手册修改的uboot 2008.10， tekkamanninja的文档没有这个版本的uboot，而uboot 2008.10版本较老，个别文件和新版uboot无法对应。抄起来还是有点难度的。
其中在tekkamanninja 文档中提到的s3c2410_nand.c文件，在uboot 2008.10版本里没有的，只好搜寻相关函数的踪迹，没s3c2410_nand.c至少也得找到到里面的函数吧，最后发现uboot 2008.10版本cpu/arm920t/s3c24X0/nand.c 文件里有相关函数的定义。。。
抄完手册，启动No NAND device found!!! 0 MiB god！失败
又重新对照手册，correct 启动仍旧打印
No NAND device found!!! 0 MiB
开始找这个问题原因很是茫然，百度，谷歌也没找到相关有效解决问题，哪里出问题了呢？最先想到的是
include/configs/micro2440.h 这个配置文件出了问题，于是仔细修改了一下，如下
#define CONFIG_CMD_NAND
#define CONFIG_ENV_IS_IN_NAND 1
//#define CONFIG_ENV_IS_IN_FLASH 1
#define CONFIG_ENV_OFFSET 0X60000
#define CONFIG_ENV_SIZE 0x20000
#if defined(CONFIG_CMD_NAND)
#define CMD_SAVEENV
#define CONFIG_NAND_S3C2410
#define CFG_NAND_BASE 0x4E000000
#define CFG_MAX_NAND_DEVICE 1 /* Max number of NAND devices */
#define SECTORSIZE 512
#define SECTORSIZE_2K 2048
#define NAND_SECTOR_SIZE SECTORSIZE
#define NAND_SECTOR_SIZE_2K SECTORSIZE_2K
#define NAND_BLOCK_MASK 511
#define NAND_BLOCK_MASK_2K 2047
#define NAND_MAX_CHIPS 1
#define CONFIG_MTD_NAND_VERIFY_WRITE
#define CONFIG_SYS_64BIT_VSPRINTF /* needed for nand_util.c */
#endif /* CONFIG_CMD_NAND */
No NAND device found!!! 0 MiB
还是不行
然后在打印语句上下功夫，代码中搜No NAND device found!!!
找到了drivers/mtd/nand/nand_base.c 这个文件
int nand_scan_ident(struct mtd_info *mtd, int maxchips)
{
int i, busw, nand_maf_id;
struct nand_chip *chip = mtd->priv;
struct nand_flash_dev *type;
/* Get buswidth to select the correct functions */
busw = chip->options & NAND_BUSWIDTH_16;
/* Set the default functions */
nand_set_defaults(chip, busw);
/* Read the flash type */
type = nand_get_flash_type(mtd, chip, busw, &nand_maf_id);
if (IS_ERR(type)) {
printk(KERN_WARNING "No NAND device found!!!\n");
chip->select_chip(mtd, -1);
return PTR_ERR(type);
}
。。。
}
打印语句是从这里出来的，看看前后代码，nand_get_flash_type（）这个函数出了问题，在追踪这个函数
发现有这么一段
chip->select_chip(mtd, 0);
/* Send the command for reading device ID */
chip->cmdfunc(mtd, NAND_CMD_READID, 0x00, -1);
/* Read manufacturer and device IDs */
*maf_id = chip->read_byte(mtd);
dev_id = chip->read_byte(mtd);
printf("dev_id = %d\n",dev_id);//这是我后来加上的，目的确认板子上读出的nandflash ID号
/* Lookup the flash id */
for (i = 0; nand_flash_ids[i].name != NULL; i++) {
if (dev_id == nand_flash_ids[i].id) {
type = &nand_flash_ids[i];
break;
编译打印，
No NAND device found!!!
dev_id = 16
0 MiB
16？找找定义ID为16的flash没 drivers/mtd/nand/nand_ids.c
struct nand_flash_dev nand_flash_ids[] = {
#ifdef CONFIG_MTD_NAND_MUSEUM_IDS
{"NAND 1MiB 5V 8-bit", 0x6e, 256, 1, 0x1000, 0},
{"NAND 2MiB 5V 8-bit", 0x64, 256, 2, 0x1000, 0},
{"NAND 4MiB 5V 8-bit", 0x6b, 512, 4, 0x2000, 0},
{"NAND 1MiB 3,3V 8-bit", 0xe8, 256, 1, 0x1000, 0},
{"NAND 1MiB 3,3V 8-bit", 0xec, 256, 1, 0x1000, 0},
{"NAND 2MiB 3,3V 8-bit", 0xea, 256, 2, 0x1000, 0},
{"NAND 4MiB 3,3V 8-bit", 0xd5, 512, 4, 0x2000, 0},
{"NAND 4MiB 3,3V 8-bit", 0xe3, 512, 4, 0x2000, 0},
{"NAND 4MiB 3,3V 8-bit", 0xe5, 512, 4, 0x2000, 0},
{"NAND 8MiB 3,3V 8-bit", 0xd6, 512, 8, 0x2000, 0},
{"NAND 8MiB 1,8V 8-bit", 0x39, 512, 8, 0x2000, 0},
{"NAND 8MiB 3,3V 8-bit", 0xe6, 512, 8, 0x2000, 0},
{"NAND 8MiB 1,8V 16-bit", 0x49, 512, 8, 0x2000, NAND_BUSWIDTH_16},
{"NAND 8MiB 3,3V 16-bit", 0x59, 512, 8, 0x2000, NAND_BUSWIDTH_16},
#endif
{"NAND 16MiB 1,8V 8-bit", 0x33, 512, 16, 0x4000, 0},
{"NAND 16MiB 3,3V 8-bit", 0x73, 512, 16, 0x4000, 0},
{"NAND 16MiB 1,8V 16-bit", 0x43, 512, 16, 0x4000, NAND_BUSWIDTH_16},
{"NAND 16MiB 3,3V 16-bit", 0x53, 512, 16, 0x4000, NAND_BUSWIDTH_16},