一、MTD系統架構

1.MTD設備體驗

FLASH在嵌入式系統中是必不可少的，它是bootloader、linux內核和文件系統的最佳載體。

在Linux內核中引入了MTD子系統為NORFLASH和NAND FLASH設備提供統一的接口，從而使得FLASH驅動的設計大為簡化。

cat /proc/mtd

每個分區對應一個塊設備

ls -l /dev/mtd*

crw-rw---- 1 0 0 90, 0 Jan 1 00:00 /dev/mtd0

crw-rw---- 1 0 0 90, 1 Jan 1 00:00 /dev/mtd0ro

crw-rw---- 1 0 0 90, 2 Jan 1 00:00 /dev/mtd1

crw-rw---- 1 0 0 90, 3 Jan 1 00:00 /dev/mtd1ro

crw-rw---- 1 0 0 90, 4 Jan 1 00:00 /dev/mtd2

crw-rw---- 1 0 0 90, 5 Jan 1 00:00 /dev/mtd2ro

brw-rw---- 1 0 0 31, 0 Jan 1 00:00 /dev/mtdblock0

brw-rw---- 1 0 0 31, 1 Jan 1 00:00 /dev/mtdblock1

brw-rw---- 1 0 0 31, 2 Jan 1 00:00 /dev/mtdblock2

2.塊設備驅動系統架構

二、YAFFS2文件系統應用

1.MTD分區設置
配置linux內核支持mtd，找到mtd接口文件，設置空間大小。
2.Yaffs2文件系統制作
將rootfs格式化生成yaffs文件系統。

/home/win/mkyaffs2image ./rootfs/ rootfs.img

3.Uboot參數設置
在uboot_tq2440includeconfigsTQ2440.h中有uboot的啟動配置選項

#define CONFIG_BZIP2

#define CONFIG_LZO

#define CONFIG_LZMA

#define CONFIG_CMD_NAND_YAFFS

#define CONFIG_BOOTARGS "console=ttySAC0 root=/dev/mtdblock3"

#define CONFIG_BOOTCOMMAND "nand read 0x30000000 kernel;bootm 0x30000000"

4.下載燒寫與啟動

在uboot中用dnw下載

三、Nandflash驅動設計
s3c2410.c/s3c24xx_nand_probe:

static int s3c24xx_nand_probe(struct platform_device *pdev,

enum s3c_cpu_type cpu_type)

{

struct s3c2410_platform_nand *plat = to_nand_plat(pdev);

struct s3c2410_nand_info *info;

struct s3c2410_nand_mtd *nmtd;

struct s3c2410_nand_set *sets;

struct resource *res;

int err = 0;

int size;

int nr_sets;

int setno;

pr_debug("s3c2410_nand_probe(%p)
", pdev);

info = kmalloc(sizeof(*info), GFP_KERNEL);

if (info == NULL) {

dev_err(&pdev->dev, "no memory for flash info
");

err = -ENOMEM;

goto exit_error;

}

memset(info, 0, sizeof(*info));

platform_set_drvdata(pdev, info);

spin_lock_init(&info->controller.lock);

init_waitqueue_head(&info->controller.wq);

/* get the clock source and enable it */

info->clk = clk_get(&pdev->dev, "nand"); //獲取時鐘，并使能

if (IS_ERR(info->clk)) {

dev_err(&pdev->dev, "failed to get clock
");

err = -ENOENT;

goto exit_error;

}

clk_enable(info->clk);

/* allocate and map the resource */

/* currently we assume we have the one resource */

res = pdev->resource;

size = res->end - res->start + 1;

info->area = request_mem_region(res->start, size, pdev->name); //地址轉換

if (info->area == NULL) {

dev_err(&pdev->dev, "cannot reserve register region
");

err = -ENOENT;

goto exit_error;

}

info->device = &pdev->dev;

info->platform = plat;

info->regs = ioremap(res->start, size);

info->cpu_type = cpu_type;

if (info->regs == NULL) {

dev_err(&pdev->dev, "cannot reserve register region
");

err = -EIO;

goto exit_error;

}

dev_dbg(&pdev->dev, "mapped registers at %p
", info->regs);

/* initialise the hardware */

err = s3c2410_nand_inithw(info); //初始化硬件

if (err != 0)

goto exit_error;

sets = (plat != NULL) ? plat->sets : NULL;

nr_sets = (plat != NULL) ? plat->nr_sets : 1;

info->mtd_count = nr_sets;

/* allocate our information */

size = nr_sets * sizeof(*info->mtds);

info->mtds = kmalloc(size, GFP_KERNEL);

if (info->mtds == NULL) {

dev_err(&pdev->dev, "failed to allocate mtd storage
");

err = -ENOMEM;

goto exit_error;

}

memset(info->mtds, 0, size);

/* initialise all possible chips */

nmtd = info->mtds;

for (setno = 0; setno < nr_sets; setno++, nmtd++) {

pr_debug("initialising set %d (%p, info %p)
", setno, nmtd, info);

s3c2410_nand_init_chip(info, nmtd, sets); //里面有校驗nandflash

nmtd->scan_res = nand_scan_ident(&nmtd->mtd, //搜索nandflash

(sets) ? sets->nr_chips : 1);

if (nmtd->scan_res == 0) {

s3c2410_nand_update_chip(info, nmtd);

nand_scan_tail(&nmtd->mtd);

s3c2410_nand_add_partition(info, nmtd, sets); //注冊分區信息

}

if (sets != NULL)

sets++;

}

err = s3c2410_nand_cpufreq_register(info);

if (err < 0) {

dev_err(&pdev->dev, "failed to init cpufreq support
");

goto exit_error;

}

if (allow_clk_stop(info)) {

dev_info(&pdev->dev, "clock idle support enabled
");

clk_disable(info->clk);

}

pr_debug("initialised ok
");

return 0;

exit_error:

s3c2410_nand_remove(pdev);

if (err == 0)

err = -EINVAL;

return err;

}

MTD通用驅動部分nand_base.c（nand_read：

static int nand_read(struct mtd_info *mtd, loff_t from, size_t len,

size_t *retlen, uint8_t *buf)

{

struct nand_chip *chip = mtd->priv;

int ret;

/* Do not allow reads past end of device */

if ((from + len) > mtd->size)

return -EINVAL;

if (!len)

return 0;

nand_get_device(chip, mtd, FL_READING);

chip->ops.len = len;

chip->ops.datbuf = buf;

chip->ops.oobbuf = NULL;

ret = nand_do_read_ops(mtd, from, &chip->ops); //進行讀操作的代碼

*retlen = chip->ops.retlen;

nand_release_device(mtd);

return ret;

}

nand_do_read_ops:

/**

* nand_do_read_ops - [Internal] Read data with ECC

*

* @mtd:MTD device structure

* @from:offset to read from

* @ops:oob ops structure

*

* Internal function. Called with chip held.

*/

static int nand_do_read_ops(struct mtd_info *mtd, loff_t from,

struct mtd_oob_ops *ops)

{

int chipnr, page, realpage, col, bytes, aligned;

struct nand_chip *chip = mtd->priv;

struct mtd_ecc_stats stats;

int blkcheck = (1 << (chip->phys_erase_shift - chip->page_shift)) - 1;

int sndcmd = 1;

int ret = 0;

uint32_t readlen = ops->len;

uint32_t oobreadlen = ops->ooblen;

uint8_t *bufpoi, *oob, *buf;

stats = mtd->ecc_stats;

chipnr = (int)(from >> chip->chip_shift);

chip->select_chip(mtd, chipnr);

realpage = (int)(from >> chip->page_shift);

page = realpage & chip->pagemask;

col = (int)(from & (mtd->writesize - 1));

buf = ops->datbuf;

oob = ops->oobbuf;

while(1) {

bytes = min(mtd->writesize - col, readlen);

aligned = (bytes == mtd->writesize);

/* Is the current page in the buffer ? */

if (realpage != chip->pagebuf || oob) {

bufpoi = aligned ? buf : chip->buffers->databuf;

if (likely(sndcmd)) {

chip->cmdfunc(mtd, NAND_CMD_READ0, 0x00, page); //實際對應了nand_command_lp,cmd命令是0

sndcmd = 0;

}

.........

}

nand_command_lp:

static void nand_command_lp(struct mtd_info *mtd, unsigned int command,

int column, int page_addr)

{

register struct nand_chip *chip = mtd->priv;

/* Emulate NAND_CMD_READOOB */

if (command == NAND_CMD_READOOB) {

column += mtd->writesize;

command = NAND_CMD_READ0;

}

/* Command latch cycle */

chip->cmd_ctrl(mtd, command & 0xff,

NAND_NCE | NAND_CLE | NAND_CTRL_CHANGE); //cmd_ctrl來源于底層驅動,在s3c2410_nand_init_chip中賦值了。

.......

}

s3c2410_nand_hwcontrol:

/* s3c2410_nand_hwcontrol

*

* Issue command and address cycles to the chip

*/

static void s3c2410_nand_hwcontrol(struct mtd_info *mtd, int cmd,

unsigned int ctrl)

{

struct s3c2410_nand_info *info = s3c2410_nand_mtd_toinfo(mtd);

if (cmd == NAND_CMD_NONE)

return;

if (ctrl & NAND_CLE)

writeb(cmd, info->regs + S3C2410_NFCMD); //往NFCONT寄存器中寫入cmd，cmd來自于nand_command,往上回溯為nand_read.其實就是發送了命令0x00

else

writeb(cmd, info->regs + S3C2410_NFADDR);

}

繼續回到nand_command_lp:

...............

if (column != -1 || page_addr != -1) {

int ctrl = NAND_CTRL_CHANGE | NAND_NCE | NAND_ALE;

/* Serially input address */

if (column != -1) {

/* Adjust columns for 16 bit buswidth */

if (chip->options & NAND_BUSWIDTH_16)

column >>= 1;

chip->cmd_ctrl(mtd, column, ctrl); //緊接著發送列地址

ctrl &= ~NAND_CTRL_CHANGE;

chip->cmd_ctrl(mtd, column >> 8, ctrl);

}

if (page_addr != -1) {

chip->cmd_ctrl(mtd, page_addr, ctrl); //發送行地址

chip->cmd_ctrl(mtd, page_addr >> 8,

NAND_NCE | NAND_ALE);

/* One more address cycle for devices > 128MiB */

if (chip->chipsize > (128 << 20))

chip->cmd_ctrl(mtd, page_addr >> 16,

NAND_NCE | NAND_ALE);

}

}

chip->cmd_ctrl(mtd, NAND_CMD_NONE, NAND_NCE | NAND_CTRL_CHANGE);

/*

* program and erase have their own busy handlers

* status, sequential in, and deplete1 need no delay

*/

switch (command) {

case NAND_CMD_CACHEDPROG:

case NAND_CMD_PAGEPROG:

case NAND_CMD_ERASE1:

case NAND_CMD_ERASE2:

case NAND_CMD_SEQIN:

case NAND_CMD_RNDIN:

case NAND_CMD_STATUS:

case NAND_CMD_DEPLETE1:

return;

/*

* read error status commands require only a short delay

*/

case NAND_CMD_STATUS_ERROR:

case NAND_CMD_STATUS_ERROR0:

case NAND_CMD_STATUS_ERROR1:

case NAND_CMD_STATUS_ERROR2:

case NAND_CMD_STATUS_ERROR3:

udelay(chip->chip_delay);

return;

case NAND_CMD_RESET:

if (chip->dev_ready)

break;

udelay(chip->chip_delay);

chip->cmd_ctrl(mtd, NAND_CMD_STATUS,

NAND_NCE | NAND_CLE | NAND_CTRL_CHANGE);

chip->cmd_ctrl(mtd, NAND_CMD_NONE,

NAND_NCE | NAND_CTRL_CHANGE);

while (!(chip->read_byte(mtd) & NAND_STATUS_READY)) ;

return;

case NAND_CMD_RNDOUT:

/* No ready / busy check necessary */

chip->cmd_ctrl(mtd, NAND_CMD_RNDOUTSTART,

NAND_NCE | NAND_CLE | NAND_CTRL_CHANGE);

chip->cmd_ctrl(mtd, NAND_CMD_NONE,

NAND_NCE | NAND_CTRL_CHANGE);

return;

case NAND_CMD_READ0:

chip->cmd_ctrl(mtd, NAND_CMD_READSTART, //這里發送了0x30命令

NAND_NCE | NAND_CLE | NAND_CTRL_CHANGE);

chip->cmd_ctrl(mtd, NAND_CMD_NONE,

NAND_NCE | NAND_CTRL_CHANGE);

/* This applies to read commands */

default:

/*

* If we don't have access to the busy pin, we apply the given

* command delay

*/

if (!chip->dev_ready) {

udelay(chip->chip_delay);

return;

}

}

/* Apply this short delay always to ensure that we do wait tWB in

* any case on any machine. */

ndelay(100);

nand_wait_ready(mtd); //wait等待

}

無欲速，無見小利。欲速，則不達；見小利，則大事不成。

總結

以上是生活随笔為你收集整理的MTD系统架构和yaffs2使用、Nandflash驱动设计的全部內容，希望文章能夠幫你解決所遇到的問題。

如果覺得生活随笔網站內容還不錯，歡迎將生活随笔推薦給好友。