1 nand flash的操作
目的：读地址A的数据，把数据B写到地址A。
问1. 原理图上NAND FLASH和S3C2440之间只有数据线，怎么传输地址？
答1．在DATA0～DATA7上既传输数据，又传输地址，当ALE为高电平时传输的是地址。
问2. 从NAND FLASH芯片手册可知，要操作NAND FLASH需要先发出命令
怎么传入命令？
答2．在DATA0～DATA7上既传输数据，又传输地址，也传输命令
当ALE为高电平时传输的是地址，
当CLE为高电平时传输的是命令
当ALE和CLE都为低电平时传输的是数据
问3. 数据线既接到NAND FLASH，也接到NOR FLASH，还接到SDRAM、DM9000等等，那么怎么避免干扰？
答3. 这些设备，要访问之必须"选中"，没有选中的芯片不会工作，相当于没接一样。（内存控制器）
问4. 假设烧写NAND FLASH，把命令、地址、数据发给它之后，
NAND FLASH肯定不可能瞬间完成烧写的，怎么判断烧写完成？
答4. 通过状态引脚RnB来判断：它为高电平表示就绪，它为低电平表示正忙
问5. 怎么操作NAND FLASH呢？
答5. 根据NAND FLASH的芯片手册，一般的过程是：
发出命令
发出地址
发出数据/读数据
2 分析nand flash的启动过程
搜"S3C24XX NAND Driver"
S3c2410.c (drivers\mtd\nand)
s3c2410_nand_inithw
s3c2410_nand_init_chip
nand_scan // 根据nand_chip的底层操作函数识别NAND FLASH，构造mtd_info
nand_scan_ident
nand_set_defaults
if (!chip->select_chip)
chip->select_chip = nand_select_chip; // 默认值不适用
if (chip->cmdfunc == NULL)
chip->cmdfunc = nand_command;
chip->cmd_ctrl(mtd, command, ctrl);
if (!chip->read_byte)
chip->read_byte = nand_read_byte;
readb(chip->IO_ADDR_R);
if (chip->waitfunc == NULL)
chip->waitfunc = nand_wait;
chip->dev_ready
nand_get_flash_type
chip->select_chip(mtd, 0);
chip->cmdfunc(mtd, NAND_CMD_READID, 0x00, -1);
*maf_id = chip->read_byte(mtd);
dev_id = chip->read_byte(mtd);
nand_scan_tail
mtd->erase = nand_erase;
mtd->read = nand_read;
mtd->write = nand_write;
s3c2410_nand_add_partition
add_mtd_partitions
add_mtd_device
list_for_each(this, &mtd_notifiers) { // 问. mtd_notifiers在哪设置
// 答. drivers/mtd/mtdchar.c,mtd_blkdev.c调用register_mtd_user
struct mtd_notifier *not = list_entry(this, struct mtd_notifier, list);
not->add(mtd);
// mtd_notify_add 和 blktrans_notify_add
先看字符设备的mtd_notify_add
class_device_create
class_device_create
再看块设备的blktrans_notify_add
list_for_each(this, &blktrans_majors) { // 问. blktrans_majors在哪设置
// 答. drivers\mtd\mdblock.c或mtdblock_ro.c register_mtd_blktrans
struct mtd_blktrans_ops *tr = list_entry(this, struct mtd_blktrans_ops, list);
tr->add_mtd(tr, mtd);
mtdblock_add_mtd (drivers\mtd\mdblock.c)
add_mtd_blktrans_dev
alloc_disk
gd->queue = tr->blkcore_priv->rq; // tr->blkcore_priv->rq = blk_init_queue(mtd_blktrans_request, &tr->blkcore_priv->queue_lock);
add_disk
3 nand flash驱动程序框架
（1）分配一个nand_chip/mtd_info结构体
（2）设置
（3）硬件相关的操作
（4）使用nand_scan/add_mtd_partitions
4 写代码
参考drivers\mtd\nand\s3c2410.c
/*参考drivers\mtd\nand\at91_nand.c*/ #include <linux/module.h>
#include <linux/types.h>
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/string.h>
#include <linux/ioport.h>
#include <linux/platform_device.h>
#include <linux/delay.h>
#include <linux/err.h>
#include <linux/slab.h>
#include <linux/clk.h> #include <linux/mtd/mtd.h>
#include <linux/mtd/nand.h>
#include <linux/mtd/nand_ecc.h>
#include <linux/mtd/partitions.h> #include <asm/io.h> #include <asm/arch/regs-nand.h>
#include <asm/arch/nand.h> struct s3c_nand_regs {
unsigned long nfconf ;
unsigned long nfcont ;
unsigned long nfcmd ;
unsigned long nfaddr ;
unsigned long nfdata ;
unsigned long nfeccd0 ;
unsigned long nfeccd1 ;
unsigned long nfeccd ;
unsigned long nfstat ;
unsigned long nfestat0;
unsigned long nfestat1;
unsigned long nfmecc0 ;
unsigned long nfmecc1 ;
unsigned long nfsecc ;
unsigned long nfsblk ;
unsigned long nfeblk ;
}; static struct mtd_info *s3c_mtd;
static struct nand_chip *s3c_nand; static struct mtd_partition s3c_nand_parts[] = {
[] = {
.name = "bootloader",
.size = 0x00040000,
.offset = ,
},
[] = {
.name = "params",
.offset = MTDPART_OFS_APPEND,
.size = 0x00020000,
},
[] = {
.name = "kernel",
.offset = MTDPART_OFS_APPEND,
.size = 0x00200000,
},
[] = {
.name = "root",
.offset = MTDPART_OFS_APPEND,
.size = MTDPART_SIZ_FULL,
}
}; static void s3c2440_select_chip(struct mtd_info *mtd, int chipnr)
{
if (chipnr == -)
{
/* 取消选中: NFCONT[1]设为1 */
s3c_nand_regs->nfcont |= (<<);
}
else
{
/* 选中: NFCONT[1]设为0 */
s3c_nand_regs->nfcont &= ~(<<);
}
} static void s3c2440_cmd_ctrl(struct mtd_info *mtd, int dat, unsigned int ctrl)
{
if (ctrl & NAND_CLE)
{
/* 发命令: NFCMMD=dat */
s3c_nand_regs->nfcmd = dat;
}
else
{
/* 发地址: NFADDR=dat */
s3c_nand_regs->nfaddr = dat;
}
} static int s3c2440_dev_ready(struct mtd_info *mtd)
{
return (s3c_nand_regs->nfstat & (<<));
} static int s3c_nand_init(void)
{
struct clk *clk;
s3c_nand = kzalloc(sizeof(struct nand_chip), GFP_KERNEL); s3c_nand_regs = ioremap(0x4E000000, sizeof(struct s3c_nand_regs)); s3c_nand->select_chip = s3c2440_select_chip;
s3c_nand->cmd_ctrl = s3c2440_cmd_ctrl;
s3c_nand->IO_ADDR_R = &s3c_nand_regs->nfdata;
s3c_nand->IO_ADDR_W = &s3c_nand_regs->nfdata;
s3c_nand->dev_ready = s3c2440_dev_ready;
s3c_nand->ecc.mode = NAND_ECC_SOFT;//enable ECC clk = clk_get(NULL, "nand");
clk_enable(clk); #define TACLS 0
#define TWRPH0 1
#define TWRPH1 0
s3c_nand_regs->nfconf = (TACLS<<) | (TWRPH0<<) | (TWRPH1<<);
s3c_nand_regs->nfcont = (<<) | (<<); s3c_mtd = kzalloc(sizeof(struct nand_chip), GFP_KERNEL);
s3c_mtd->owner = THIS_MODULE;
s3c_mtd->priv = s3c_nand;
nand_scan(s3c_mtd, );//识别nand falsh，构造mtd_info add_mtd_partitions(s3c_mtd, s3c_nand_parts,); return ;
} static void s3c_nand_exit(void)
{
del_mtd_partitions(s3c_mtd);
kfree(s3c_mtd);
iounmap(s3c_nand_regs);
kfree(s3c_nand);
} module_init(s3c_nand_init);
module_exit(s3c_nand_exit); MODULE_LICENSE("GPL");
s3c_nand.c