MTD原始设备与FLASH硬件驱动的对话 (一) （转）
时间：10-02
整理：3721RD
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SIMSun">看了<<linux MTD源代码分析>>后对以MTD的分层结构以及各层的分工情况有了大致的了解，然而各层之间是如何进行对话的呢，对于这个问题，<<Linux MTD源代码分析>>上没有详细的去说明。
小弟抽空研究了一下，打算从下到上，在从上到下，分两条主线来研究一下MTD原始设备与FLASH硬件驱动的对话(MTD原始设备与更上层的对话留待以后再研究)。
以下是第一部分，从下到上的介绍FLASH硬件驱动与MTD原始设备是如何建立联系的。
1、首先从入口函数开始：
static int s3c24xx_nand_probe(struct device *dev, int is_s3c2440)
{
struct platform_device *pdev = to_platform_device(dev);
struct s3c2410_platform_nand *plat = to_nand_plat(dev);
//获取nand flash配置用结构体数据(dev.c中定义，详细见附录部分)
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)/n", dev);
info = kmalloc(sizeof(*info), GFP_KERNEL);
if (info == NULL) {
printk(KERN_ERR PFX "no memory for flash info/n");
err = -ENOMEM;
goto exit_error;
}
memzero(info, sizeof(*info));
dev_set_drvdata(dev, info); //以后有用
SPIn_lock_init(&info->controller.lock); //初始化自旋锁
init_waitqueue_head(&info->controller.wq); //初始化等待队列
/* get the clock source and enable it */
info->clk = clk_get(dev, "nand");
if (IS_ERR(info->clk)) {
printk(KERN_ERR PFX "failed to get clock");
err = -ENOENT;
goto exit_error;
}
clk_use(info->clk);
clk_enable(info->clk);
/* allocate and map the resource */
/* currently we assume we have the one resource */
res = pdev->resource; //提取dev.c中定义的与设备相关的资源
size = res->end - res->start + 1;
info->area = request_mem_region(res->start, size, pdev->name);
if (info->area == NULL) {
printk(KERN_ERR PFX "cannot reserve register region/n");
err = -ENOENT;
goto exit_error;
}
info->device = dev;
info->platform = plat; //保存好struct s3c2410_platform_nand结构数据
info->regs = ioremap(res->start, size);//映射nand flash用到的寄存器
info->is_s3c2440 = is_s3c2440;
if (info->regs == NULL) {
printk(KERN_ERR PFX "cannot reserve register region/n");
err = -EIO;
goto exit_error;
}
printk(KERN_INFO PFX "mapped registers at %p/n", info->regs);
/* initialise the hardware */
err = s3c2410_nand_inithw(info, dev);
//初始化s3c2410 nand flash控制，主要是配置S3C2410_nfcONF寄存器
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;
//我的板上只有一块nand flash，配置信息见plat-sets，数目为1。
/* allocate our information */
size = nr_sets * sizeof(*info->mtds);
info->mtds = kmalloc(size, GFP_KERNEL);
if (info->mtds == NULL) {
printk(KERN_ERR PFX "failed to allocate mtd storage/n");
err = -ENOMEM;
goto exit_error;
}
memzero(info->mtds, size);
/* initialise all possible chips */
nmtd = info->mtds;
for (setno = 0; setno < nr_sets; setno++, nmtd++) {
pr_debug("initialising set %d (%p, info %p)/n",
setno, nmtd, info);
s3c2410_nand_init_chip(info, nmtd, sets);
nmtd->scan_res = nand_scan(&nmtd->mtd,
(sets) ? sets->nr_chips : 1);//为什么使用set->nr_chips(还没配置的东西)?
if (nmtd->scan_res == 0) {
s3c2410_nand_add_partition(info, nmtd, sets);
}
if (sets ！= NULL)
sets++;
}
pr_debug("initialised ok/n");
return 0;
exit_error:
s3c2410_nand_remove(dev);
if (err == 0)
err = -EINVAL;
return err;
}
//初始化代表一片flash的struct nand_chip结构
static void s3c2410_nand_init_chip(struct s3c2410_nand_info *info,
struct s3c2410_nand_mtd *nmtd,
struct s3c2410_nand_set *set)
{
struct nand_chip *chip = &nmtd->chip;
chip->IO_ADDR_R = info->regs + S3C2410_NFDATA; //读地址
chip->IO_ADDR_W = info->regs + S3C2410_NFDATA; //写地址
chip->hwcontrol = s3c2410_nand_hwcontrol;
chip->dev_ready = s3c2410_nand_devready; //ready状态查询
chip->write_buf = s3c2410_nand_write_buf; //写函数
chip->read_buf = s3c2410_nand_read_buf; //读函数
chip->select_chip = s3c2410_nand_select_chip; //片选函数
chip->chip_delay = 50;
chip->priv = nmtd;
chip->options = 0;
chip->controller = &info->controller;
if (info->is_s3c2440) {
chip->IO_ADDR_R = info->regs + S3C2440_NFDATA;
chip->IO_ADDR_W = info->regs + S3C2440_NFDATA;
chip->hwcontrol = s3c2440_nand_hwcontrol;
}
nmtd->info = info;
nmtd->mtd.priv = chip;
//nand_scan函数中会调用struct nand_chip *this = mtd->priv取出该struct nand_chip结构
nmtd->set = set;
if (hardware_ecc) {
chip->correct_data = s3c2410_nand_correct_data;
chip->enable_hwecc = s3c2410_nand_enable_hwecc;
chip->calculate_ecc = s3c2410_nand_calculate_ecc;
chip->eccmode = NAND_ECC_HW3_512;
chip->autooob = &nand_hw_eccoob;
if (info->is_s3c2440) {
chip->enable_hwecc = s3c2440_nand_enable_hwecc;
chip->calculate_ecc = s3c2440_nand_calculate_ecc;
}
} else {
chip->eccmode = NAND_ECC_SOFT; //ECC的类型
}
}
/* command and control functions
*
* 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)
{
struct s3c2410_nand_info *info = s3c2410_nand_mtd_toinfo(mtd);
struct nand_chip *chip = mtd->priv;
switch (cmd) {
case NAND_CTL_SETNCE:
case NAND_CTL_CLRNCE:
printk(KERN_ERR "%s: called for NCE/n", __FUNCTION__);
break;
case NAND_CTL_SETCLE:
chip->IO_ADDR_W = info->regs + S3C2410_NFCMD;//写命令
break;
case NAND_CTL_SETALE:
chip->IO_ADDR_W = info->regs + S3C2410_NFADDR;//写地址
break;
/* NAND_CTL_CLRCLE: */
/* NAND_CTL_CLRALE: */
default:
chip->IO_ADDR_W = info->regs + S3C2410_NFDATA;//写数据
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)
{
struct s3c2410_nand_info *info = s3c2410_nand_mtd_toinfo(mtd);
if (info->is_s3c2440)
return readb(info->regs + S3C2440_NFSTAT) & S3C2440_NFSTAT_READY;
return readb(info->regs + S3C2410_NFSTAT) & S3C2410_NFSTAT_BUSY;//返回nand flash都忙标志
}
static void s3c2410_nand_write_buf(struct mtd_info *mtd,
const u_char *buf, int len)
{
struct nand_chip *this = mtd->priv;
writesb(this->IO_ADDR_W, buf, len);//写操作
}
static void s3c2410_nand_read_buf(struct mtd_info *mtd, u_char *buf, int len)
{
struct nand_chip *this = mtd->priv;
reADSb(this->IO_ADDR_R, buf, len);//读操作
}
/* select chip */
/*
* 根据chip都值设置nand flash都片选信号:
* chip = -1 -- 禁用nand flash
* chip ！=-1 -- 选择对应的nand flash
*/
static void s3c2410_nand_select_chip(struct mtd_info *mtd, int chip)
{
struct s3c2410_nand_info *info;
struct s3c2410_nand_mtd *nmtd;
struct nand_chip *this = mtd->priv;
void __iomem *reg;
unsigned long cur;
unsigned long bit;
nmtd = this->priv;
info = nmtd->info;
bit = (info->is_s3c2440) ? S3C2440_NFCONT_nFCE : S3C2410_NFCONF_nFCE;
reg = info->regs+((info->is_s3c2440) ? S3C2440_NFCONT:S3C2410_NFCONF);
cur = readl(reg);
if (chip == -1) {
cur |= bit;
} else {
if (nmtd->set ！= NULL && chip > nmtd->set->nr_chips) {
printk(KERN_ERR PFX "chip %d out of range/n", chip);
return;
}
if (info->platform ！= NULL) {
if (info->platform->select_chip ！= NULL)
(info->platform->select_chip)(nmtd->set, chip);
}
cur &= ~bit;
}
writel(cur, reg);
}
注：
s3c2410_nand_init_chip填充struct nand_chip的一部分成员，nand_scan以通用nand flash的标准进行检测，并填充struct nand_chip的其它成员，必要时根据检测结果进行取舍。
int nand_scan (struct mtd_info *mtd, int maxchips)
{
int i, nand_maf_id, nand_dev_id, busw, maf_id;
struct nand_chip *this = mtd->priv; //取出struct nand_chip结构
/* Get buswidth to select the correct functions*/
busw = this->options & NAND_BUSWIDTH_16; //nand flash的位宽
/* check for proper chip_delay setup, set 20us if not */
if (！this->chip_delay)
this->chip_delay = 20;
/* check, if a user supplied command function given */
if (this->cmdfunc == NULL) //填充命令函数
this->cmdfunc = nand_command;
/* check, if a user supplied wait function given */
if (this->waitfunc == NULL) //填充等待函数
this->waitfunc = nand_wait;
if (！this->select_chip) //s3c2410_nand_init_chip中已定义
this->select_chip = nand_select_chip;
if (！this->write_byte) //使用默认的
this->write_byte = busw ? nand_write_byte16 : nand_write_byte;
if (！this->read_byte) //使用默认的
this->read_byte = busw ? nand_read_byte16 : nand_read_byte;
if (！this->write_word) //使用默认的
this->write_word = nand_write_word;
if (！this->read_word) //使用默认的
this->read_word = nand_read_word;
if (！this->block_bad) //使用默认的
this->block_bad = nand_block_bad;
if (！this->block_markbad) //使用默认的
this->block_markbad = nand_default_block_markbad;
if (！this->write_buf) //s3c2410_nand_init_chip中已定义
this->write_buf = busw ? nand_write_buf16 : nand_write_buf;
if (！this->read_buf) //s3c2410_nand_init_chip中已定义
this->read_buf = busw ? nand_read_buf16 : nand_read_buf;
if (！this->verify_buf) //使用默认的
this->verify_buf = busw ? nand_verify_buf16 : nand_verify_buf;
if (！this->scan_bbt) //使用默认的
this->scan_bbt = nand_default_bbt;
/* Select the device */
this->select_chip(mtd, 0); //片选，可惜在s3c2410 nand flash控制器中此操作为空
/* Send the command for reading device ID */
this->cmdfunc (mtd, NAND_CMD_READID, 0x00, -1);//发送读ID命令
/* Read manufacturer and device IDs */
nand_maf_id = this->read_byte(mtd); //读取生产商ID
nand_dev_id = this->read_byte(mtd); //读取设备ID
/* Print and store flash device information */
for (i = 0; nand_flash_ids.name ！= NULL; i++) {
//保存着nand flash资料的nand_flash_ids表在include/linux/mtd/nand_ids.c文件中，详细见附录
if (nand_dev_id ！= nand_flash_ids.id) //比较设备ID
continue;
if (！mtd->name) mtd->name = nand_flash_ids.name; //填充设备名
this->chipsize = nand_flash_ids.chipsize << 20; //填充设备大小
/* New devices have all the information in additional id bytes */
if (！nand_flash_ids.pagesize) {
int extid;
/* The 3rd id byte contains non relevant data ATM */
extid = this->read_byte(mtd);
/* The 4th id byte is the important one */
extid = this->read_byte(mtd);
/* Calc pagesize */
mtd->oobblock = 1024 << (extid & 0x3);
extid >>= 2;
/* Calc oobsize */
mtd->oobsize = (8 << (extid & 0x03)) * (mtd->oobblock / 512);
extid >>= 2;
/* Calc blocksize. Blocksize is multiples of 64KiB */
mtd->erasesize = (64 * 1024) << (extid & 0x03);
extid >>= 2;
/* Get buswidth information */
busw = (extid & 0x01) ? NAND_BUSWIDTH_16 : 0;
} else {
/* Old devices have this data hardcoded in the
* device id table */
mtd->erasesize = nand_flash_ids.erasesize; //填充檫除单元大小(16k)
mtd->oobblock = nand_flash_ids.pagesize; //填充页大小(512)
mtd->oobsize = mtd->oobblock / 32; //oob大小(512/32=16)
busw = nand_flash_ids.options & NAND_BUSWIDTH_16;//获取nand flash表中定义的位宽
}
/* Try to identify manufacturer */ //比较生产商ID
for (maf_id = 0; nand_manuf_ids[maf_id].id ！= 0x0; maf_id++) {
if (nand_manuf_ids[maf_id].id == nand_maf_id)
break;
}
/* Check, if buswidth is correct. Hardware drivers should set
* this correct ！ */
/用户定义的位宽与芯片实际的位宽不一致，取消nand flash的片选
if (busw ！= (this->options & NAND_BUSWIDTH_16)) {
printk (KERN_INFO "NAND device: Manufacturer ID:"
" 0x%02x, Chip ID: 0x%02x (%s %s)/n", nand_maf_id, nand_dev_id,
nand_manuf_ids[maf_id].name , mtd->name);
printk (KERN_WARNING
"NAND bus width %d instead %d bit/n",
(this->options & NAND_BUSWIDTH_16) ? 16 : 8,
busw ? 16 : 8);
this->select_chip(mtd, -1);//在s3c2410 nand flash控制器驱动中，此操作为空操作
return 1;
}
/* Calculate the address shift fROM the page size */
//计算页、可檫除单元、nand flash大小的偏移值
this->page_shift = ffs(mtd->oobblock) - 1;
this->bbt_erase_shift = this->phys_erase_shift = ffs(mtd->erasesize) - 1;
this->chip_shift = ffs(this->chipsize) - 1;
/* Set the bad block position */
//标注此nand flash为大页还是小页?
this->badblockpos = mtd->oobblock > 512 ?
NAND_LARGE_BADBLOCK_POS : NAND_SMALL_BADBLOCK_POS;
/* Get chip options, preserve non chip based options */
//用户没指定的选项从nand flash表中获取补上
this->options &= ~NAND_CHIPOPTIONS_MSK;
this->options |= nand_flash_ids.options & NAND_CHIPOPTIONS_MSK;
/* Set this as a default. Board drivers can override it, if neccecary */
this->options |= NAND_NO_AUTOINCR;
/* Check if this is a not a samsung device. Do not clear the options
* for chips which are not having an extended id.
*/
if (nand_maf_id ！= NAND_MFR_SAMSUNG && ！nand_flash_ids.pagesize)
this->options &= ~NAND_SAMSUNG_LP_OPTIONS;
/* Check for AND chips with 4 page planes */
if (this->options & NAND_4PAGE_ARRAY)
this->erase_cmd = multi_erase_cmd;
else
this->erase_cmd = single_erase_cmd;
/* Do not replace user supplied command function ！ */
if (mtd->oobblock > 512 && this->cmdfunc == nand_command)
this->cmdfunc = nand_command_lp;
printk (KERN_INFO "NAND device: Manufacturer ID:"
" 0x%02x, Chip ID: 0x%02x (%s %s)/n", nand_maf_id, nand_dev_id,
nand_manuf_ids[maf_id].name , nand_flash_ids.name);
break;
}//好的，检测结束^_^
if (！nand_flash_ids.name) {
printk (KERN_WARNING "No NAND device found！/n");
this->select_chip(mtd, -1);
return 1;
}
//统计一下同种类型的nand flash有多少块(我板上只有一块)
for (i=1; i < maxchips; i++) {
this->select_chip(mtd, i);
/* Send the command for reading device ID */
this->cmdfunc (mtd, NAND_CMD_READID, 0x00, -1);
/* Read manufacturer and device IDs */
if (nand_maf_id ！= this->read_byte(mtd) ||
nand_dev_id ！= this->read_byte(mtd))
break;
}
if (i > 1)
printk(KERN_INFO "%d NAND chips detected/n", i);
/* Allocate buffers, if neccecary */
if (！this->oob_buf) {
size_t len;
//求出一个檫除单元64K中oob所占用的总空间
len = mtd->oobsize << (this->phys_erase_shift - this->page_shift);
this->oob_buf = kmalloc (len, GFP_KERNEL);
if (！this->oob_buf) {
printk (KERN_ERR "nand_scan(): Cannot allocate oob_buf/n");
return -ENOMEM;
}
this->options |= NAND_OOBBUF_ALLOC;//oob空间已分配，置相应的标志位
}
if (！this->data_buf) {
size_t len;
len = mtd->oobblock + mtd->oobsize;//512+16=128
this->data_buf = kmalloc (len, GFP_KERNEL);
if (！this->data_buf) {
if (this->options & NAND_OOBBUF_ALLOC)
kfree (this->oob_buf);
printk (KERN_ERR "nand_scan(): Cannot allocate data_buf/n");
return -ENOMEM;
}
this->options |= NAND_DATABUF_ALLOC;//数据空间已分配，置相应的标志位
}
/* Store the number of chips and calc total size for mtd */
this->numchips = i;//记录nand flash片数
mtd->size = i * this->chipsize;//计算出nand flash总大小
/* Convert chipsize to number of pages per chip -1. */
this->pagemask = (this->chipsize >> this->page_shift) - 1;//(64M>>9)-1=128k-1=0x1ffff
/* Preset the internal oob buffer */
//oob_buf全部置为0xff
mEMSet(this->oob_buf, 0xff, mtd->oobsize << (this->phys_erase_shift - this->page_shift));
/* If no default placement scheme is given, select an
* appropriate one */
if (！this->autooob) { //我们选用的是NAND_ECC_SOFT，autooob未设置
/* Select the appropriate default oob placement scheme for
* placement agnostic filesystems */
switch (mtd->oobsize) {
case 8:
this->autooob = &nand_oob_8;
break;
case 16:
this->autooob = &nand_oob_16;//我们的nand flash属于这一类
break;
case 64:
this->autooob = &nand_oob_64;
break;
default:
printk (KERN_WARNING "No oob scheme defined for oobsize %d/n",
mtd->oobsize);
BUG();
}
}
注：
ECC的东西不是很懂，先跳过^_^
/* The number of bytes available for the filesystem to place fs dependend
* oob data */
mtd->oobavail = 0;
for (i = 0; this->autooob->oobfree[1]; i++)
mtd->oobavail += this->autooob->oobfree[1];
/*
* check ECC mode, default to software
* if 3byte/512byte hardware ECC is selected and we have 256 byte pagesize
* fallback to software ECC
*/
this->eccsize = 256; /* set default eccsize */
this->eccbytes = 3;
switch (this->eccmode) {
case NAND_ECC_HW12_2048:
if (mtd->oobblock < 2048) {
printk(KERN_WARNING "2048 byte HW ECC not possible on %d byte page size, fallback to SW ECC/n",
mtd->oobblock);
this->eccmode = NAND_ECC_SOFT;
this->calculate_ecc = nand_calculate_ecc;
this->correct_data = nand_correct_data;
} else
this->eccsize = 2048;
break;
case NAND_ECC_HW3_512:
case NAND_ECC_HW6_512:
case NAND_ECC_HW8_512:
if (mtd->oobblock == 256) {
printk (KERN_WARNING "512 byte HW ECC not possible on 256 Byte pagesize, fallback to SW ECC /n");
this->eccmode = NAND_ECC_SOFT;
this->calculate_ecc = nand_calculate_ecc;
this->correct_data = nand_correct_data;
} else
this->eccsize = 512; /* set eccsize to 512 */
break;
case NAND_ECC_HW3_256:
break;
case NAND_ECC_NONE:
printk (KERN_WARNING "NAND_ECC_NONE selected by board driver. This is not recommended ！/n");
this->eccmode = NAND_ECC_NONE;
break;
case NAND_ECC_SOFT:
this->calculate_ecc = nand_calculate_ecc;
this->correct_data = nand_correct_data;
break;
default:
printk (KERN_WARNING "Invalid NAND_ECC_MODE %d/n", this->eccmode);
BUG();
}
/* Check hardware ecc function availability and adjust number of ecc bytes per
* calculation step
*/
switch (this->eccmode) {
case NAND_ECC_HW12_2048:
this->eccbytes += 4;
case NAND_ECC_HW8_512:
this->eccbytes += 2;
case NAND_ECC_HW6_512:
this->eccbytes += 3;
case NAND_ECC_HW3_512:
case NAND_ECC_HW3_256:
if (this->calculate_ecc && this->correct_data && this->enable_hwecc)
break;
printk (KERN_WARNING "No ECC functions supplied, Hardware ECC not possible/n");
BUG();
}
mtd->eccsize = this->eccsize;
/* Set the number of read / write steps for one page to ensure ECC generation */
switch (this->eccmode) {
case NAND_ECC_HW12_2048:
this->eccsteps = mtd->oobblock / 2048;
break;
case NAND_ECC_HW3_512:
case NAND_ECC_HW6_512:
case NAND_ECC_HW8_512:
this->eccsteps = mtd->oobblock / 512;
break;
case NAND_ECC_HW3_256:
case NAND_ECC_SOFT:
this->eccsteps = mtd->oobblock / 256;
break;
case NAND_ECC_NONE:
this->eccsteps = 1;
break;
}
/* Initialize state, waitqueue and spinlock */
this->state = FL_READY;
init_waitqueue_head (&this->wq);
spin_lock_init (&this->chip_lock);
/* De-select the device */
this->select_chip(mtd, -1);
/* Invalidate the pagebuffer reference */
this->pagebuf = -1;
/* Fill in remaining MTD driver data */
//填充mtd结构的其它部分
mtd->type = MTD_NANDFLASH;
mtd->flags = MTD_CAP_NANDFLASH | MTD_ECC;
mtd->ecctype = MTD_ECC_SW;
mtd->erase = nand_erase;
mtd->point = NULL;
mtd->unpoint = NULL;
mtd->read = nand_read;
/* nand_read->nand_do_read_ecc->read_buf->s3c2410_nand_read_buf */
mtd->write = nand_write;
/* nand_write->nand_write_ecc->nand_write_page->write_buf->s3c2410_nand_write_buf */
mtd->read_ecc = nand_read_ecc;
mtd->write_ecc = nand_write_ecc;
mtd->read_oob = nand_read_oob;
mtd->write_oob = nand_write_oob;
mtd->readv = NULL;
mtd->writev = nand_writev;
mtd->writev_ecc = nand_writev_ecc;
mtd->sync = nand_sync;
mtd->lock = NULL;
mtd->unlock = NULL;
mtd->suspend = NULL;
mtd->resume = NULL;
mtd->block_isbad = nand_block_isbad;
mtd->block_markbad = nand_block_markbad;
/* and make the autooob the default one */
meMCPy(&mtd->oobinfo, this->autooob, sizeof(mtd->oobinfo));
mtd->owner = THIS_MODULE;
/* Check, if we should skip the bad block table scan */
if (this->options & NAND_SKIP_BBTSCAN)
return 0;
/* Build bad block table */
return this->scan_bbt (mtd);
}
/**
* nand_command - [DEFAULT] Send command to NAND device
* @mtd: MTD device structure
* @command: the command to be sent
* @column: the column address for this command, -1 if none
* @page_addr: the page address for this command, -1 if none
*
* Send command to NAND device. This function is used for small page
* devices (256/512 Bytes per page)
*/
static void nand_command (struct mtd_info *mtd, unsigned command, int column, int page_addr)
{
register struct nand_chip *this = mtd->priv;
/* Begin command latch cycle */
this->hwcontrol(mtd, NAND_CTL_SETCLE); //选择写入S3C2410_NFCMD寄存器
/*
* Write out the command to the device.
*/
if (command == NAND_CMD_SEQIN) {
int reADCmd;
if (column >= mtd->oobblock) { //读/写位置超出512，读oob_data
/* OOB area */
column -= mtd->oobblock;
readcmd = NAND_CMD_READOOB;
} else if (column < 256) { //读/写位置在前512，使用read0命令
/* First 256 bytes --> READ0 */
readcmd = NAND_CMD_READ0;
} else { //读/写位置在后512，使用read1命令
column -= 256;
readcmd = NAND_CMD_READ1;
}
this->write_byte(mtd, readcmd); //写入具体命令
}
this->write_byte(mtd, command);
/* Set ALE and clear CLE to start address cycle */
/* 清楚CLE，锁存命令；置位ALE，开始传输地址 */
this->hwcontrol(mtd, NAND_CTL_CLRCLE); //锁存命令
if (column ！= -1 || page_addr ！= -1) {
this->hwcontrol(mtd, NAND_CTL_SETALE); //选择写入S3C2410_NFADDR寄存器
/* Serially input address */
if (column ！= -1) {
/* Adjust columns for 16 bit buswidth */
if (this->options & NAND_BUSWIDTH_16)
column >>= 1;
this->write_byte(mtd, column); //写入列地址
}
if (page_addr ！= -1) { //写入页地址(分三个字节写入)
this->write_byte(mtd, (unsigned char) (page_addr & 0xff));
this->write_byte(mtd, (unsigned char) ((page_addr >> 8) & 0xff));
/* One more address cycle for devices > 32MiB */
if (this->chipsize > (32 << 20))
this->write_byte(mtd, (unsigned char) ((page_addr >> 16) & 0x0f));
}
/* Latch in address */
/* 锁存地址 */
this->hwcontrol(mtd, NAND_CTL_CLRALE);
}
/*
* program and erase have their own busy handlers
* status and sequential in needs no delay
*/
switch (command) {
case NAND_CMD_PAGEPROG:
case NAND_CMD_ERASE1:
case NAND_CMD_ERASE2:
case NAND_CMD_SEQIN:
case NAND_CMD_STATUS:
return;
case NAND_CMD_RESET: //复位操作
// 等待nand flash become ready
if (this->dev_ready) //判断nand flash 是否busy(1:ready 0:busy)
break;
udelay(this->chip_delay);
this->hwcontrol(mtd, NAND_CTL_SETCLE);
this->write_byte(mtd, NAND_CMD_STATUS);
this->hwcontrol(mtd, NAND_CTL_CLRCLE);
while ( ！(this->read_byte(mtd) & NAND_STATUS_READY));
return;
/* This applies to read commands */
default:
/*
* If we don't have access to the busy pin, we apply the given
* command delay
*/
if (！this->dev_ready) {
udelay (this->chip_delay);//稍作延迟
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 for the ready pin, after a command
* The timeout is catched later.
*/
static void nand_wait_ready(struct mtd_info *mtd)
{
struct nand_chip *this = mtd->priv;
unsigned long timeo = jiffies + 2;
/* wait until command is processed or timeout occures */
do {
if (this->dev_ready(mtd)) //简单调用this->dev_ready(s3c2410_nand_devready)函数 等待nand flash become ready
return;
touch_softlockup_watchdog();
} while (time_before(jiffies, timeo));
}
/**
* nand_wait - [DEFAULT] wait until the command is done
* @mtd: MTD device structure
* @this: NAND chip structure
* @state: state to select the max. timeout value
*
* Wait for command done. This applies to erase and program only
* Erase can take up to 400ms and program up to 20ms according to
* general NAND and SmartMedia specs
*
*/
/* 等待知道命令传输完成，适用于檫除和写入命令 */
static int nand_wait(struct mtd_info *mtd, struct nand_chip *this, int state)
{
unsigned long timeo = jiffies;
int status;
if (state == FL_ERASING)
timeo += (HZ * 400) / 1000;//檫除操作的话，时间相对要长一些
else
timeo += (HZ * 20) / 1000;
/* Apply this short delay always to ensure that we do wait tWB in
* any case on any machine. */
ndelay (100);
if ((state == FL_ERASING) && (this->options & NAND_IS_AND))
this->cmdfunc (mtd, NAND_CMD_STATUS_MULTI, -1, -1);
else
this->cmdfunc (mtd, NAND_CMD_STATUS, -1, -1);
while (time_before(jiffies, timeo)) {
/* Check, if we were interrupted */
if (this->state ！= state)
return 0;
/* 等待nand flash become ready */
if (this->dev_ready) {
if (this->dev_ready(mtd))
break;
} else {
if (this->read_byte(mtd) & NAND_STATUS_READY)
break;
}
cond_resched();
}
status = (int) this->read_byte(mtd);
return status;
}
/**
* nand_block_bad - [DEFAULT] Read bad block marker from the chip
* 检查nand flash中某一页是否为坏块
* @mtd: MTD device structure
* @ofs: offset from device start
* @getchip: 0, if the chip is already selected
*
* Check, if the block is bad.
*/
static int nand_block_bad(struct mtd_info *mtd, loff_t ofs, int getchip)
{
int page, chipnr, res = 0;
struct nand_chip *this = mtd->priv;
u16 bad;
if (getchip) {
page = (int)(ofs >> this->page_shift);
chipnr = (int)(ofs >> this->chip_shift);
/* Grab the lock and see if the device is available */
nand_get_device (this, mtd, FL_READING);
/* Select the NAND device */
this->select_chip(mtd, chipnr);
} else
page = (int) ofs;
if (this->options & NAND_BUSWIDTH_16) {
this->cmdfunc (mtd, NAND_CMD_READOOB, this->badblockpos & 0xFE, page & this->pagemask);
bad = cpu_to_le16(this->read_word(mtd));
if (this->badblockpos & 0x1)
bad >>= 1;
if ((bad & 0xFF) ！= 0xff)
res = 1;
} else {
this->cmdfunc (mtd, NAND_CMD_READOOB, this->badblockpos, page & this->pagemask);
/* 发送读oob_data命令(oob_data的badblockpos (第6)位记录着坏块标志) */
if (this->read_byte(mtd) ！= 0xff)//坏块
res = 1;
}
if (getchip) {
/* Deselect and wake up anyone waiting on the device */
nand_release_device(mtd);
}
return res;
}
/**
* nand_default_block_markbad - [DEFAULT] mark a block bad
* 标志坏块
* @mtd: MTD device structure
* @ofs: offset from device start
*
* This is the default implementation, which can be overridden by
* a hardware specific driver.
*/
static int nand_default_block_markbad(struct mtd_info *mtd, loff_t ofs)
{
struct nand_chip *this = mtd->priv;
u_char buf[2] = {0, 0};
size_t retlen;
int block;
/* Get block number */
block = ((int) ofs) >> this->bbt_erase_shift;
if (this->bbt)
this->bbt[block >> 2] |= 0x01 << ((block & 0x03) << 1);
/*
这个暂时不是很好说：内核维护一个标志bad block表，使用2bit来表示1block。
这个表在开机的时候通过扫描nand flash每个block的头两页的oob数据来生成，
发现坏块后至相应的block标志位为非零(有时候至3，但有时候至1，还没搞明白有什么不同)
*/
/* Do we have a flash based bad block table ? */
if (this->options & NAND_USE_FLASH_BBT)//samsun nand flash不属于这种，暂时不去研究，以后同
return nand_update_bbt (mtd, ofs);
/* We write two bytes, so we dont have to mess with 16 bit access */
ofs += mtd->oobsize + (this->badblockpos & ~0x01);//?
return nand_write_oob (mtd, ofs , 2, &retlen, buf);
}
/**
* nand_verify_buf - [DEFAULT] Verify chip data against buffer
* 检验nand flash与buffer的数据是否一致
* @mtd: MTD device structure
* @buf: buffer containing the data to compare
* @len: number of bytes to compare
*
* Default verify function for 8bit buswith
*/
static int nand_verify_buf(struct mtd_info *mtd, const u_char *buf, int len)
{
int i;
struct nand_chip *this = mtd->priv;
for (i=0; i<len; i++)
if (buf ！= readb(this->IO_ADDR_R))
return -EFAULT;
return 0;
}
/**
* nand_default_bbt - [NAND Interface] Select a default bad block table for the device
* @mtd: MTD device structure
*
* This function selects the default bad block table
* support for the device and calls the nand_scan_bbt function
*
*/
int nand_default_bbt (struct mtd_info *mtd)
{
struct nand_chip *this = mtd->priv;
/* Default for AG-AND. We must use a flash based
* bad block table as the devices have factory marked
* _good_ blocks. Erasing those blocks leads to loss
* of the good / bad information, so we _must_ store
* this information in a good / bad table during
* startup
*/
if (this->options & NAND_IS_AND) {
/* Use the default pattern descriptors */
if (！this->bbt_td) {
this->bbt_td = &bbt_main_descr;
this->bbt_md = &bbt_mirror_descr;
}
this->options |= NAND_USE_FLASH_BBT;
return nand_scan_bbt (mtd, &agand_flashbased);
}
/* Is a flash based bad block table requested ? */
if (this->options & NAND_USE_FLASH_BBT) {
/* Use the default pattern descriptors */
if (！this->bbt_td) {
this->bbt_td = &bbt_main_descr;
this->bbt_md = &bbt_mirror_descr;
}
if (！this->badblock_pattern) {
this->badblock_pattern = (mtd->oobblock > 512) ?
&largepage_flashbased : &smallpage_flashbased;
}
} else { //samsun nand flash的坏块表不存在与nand flash里面，需要扫描来生成。
this->bbt_td = NULL;
this->bbt_md = NULL;
if (！this->badblock_pattern) {
this->badblock_pattern = (mtd->oobblock > 512) ?
&largepage_memorybased : &smallpage_memorybased;
}
}
return nand_scan_bbt (mtd, this->badblock_pattern);
}
/**
* nand_scan_bbt - [NAND Interface] scan, find, read and maybe create bad block table(s)
* @mtd: MTD device structure
* @bd: descriptor for the good/bad block search pattern
*
* The function checks, if a bad block table(s) is/are already
* available. If not it scans the device for manufacturer
* marked good / bad blocks and writes the bad block table(s) to
* the selected place.
*
* The bad block table memory is allocated here. It must be freed
* by calling the nand_free_bbt function.
*
*/
int nand_scan_bbt (struct mtd_info *mtd, struct nand_bbt_descr *bd)
{
struct nand_chip *this = mtd->priv;
int len, res = 0;
uint8_t *buf;
struct nand_bbt_descr *td = this->bbt_td;
struct nand_bbt_descr *md = this->bbt_md;
len = mtd->size >> (this->bbt_erase_shift + 2);
/* Allocate memory (2bit per block) */
/* 2bit per block=(2/8)byte per block，所以上面要多右移2位 */
this->bbt = kmalloc (len, GFP_KERNEL);
if (！this->bbt) {
printk (KERN_ERR "nand_scan_bbt: Out of memory/n");
return -ENOMEM;
}
/* Clear the memory bad block table */
memset (this->bbt, 0x00, len);
/* If no primary table decriptor is given, scan the device
* to build a memory based bad block table
*/
if (！td) {
if ((res = nand_memory_bbt(mtd, bd))) {
printk (KERN_ERR "nand_bbt: Can't scan flash and build the RAM-based BBT/n");
kfree (this->bbt);
this->bbt = NULL;
}
return res;
}
/* Allocate a temporary buffer for one eraseblock incl. oob */
/* 分配1 block所需要的oob data空间 */
len = (1 << this->bbt_erase_shift);
len += (len >> this->page_shift) * mtd->oobsize;
buf = kmalloc (len, GFP_KERNEL);
if (！buf) {
printk (KERN_ERR "nand_bbt: Out of memory/n");
kfree (this->bbt);
this->bbt = NULL;
return -ENOMEM;
}
//由于td、md均为NULL，一下函数基本不起作用，先不去研究它
/* Is the bbt at a given page ? */
if (td->options & NAND_BBT_ABSPAGE) {
res = read_abs_bbts (mtd, buf, td, md);
} else {
/* Search the bad block table using a pattern in oob */
res = search_read_bbts (mtd, buf, td, md);
}
if (res)
res = check_create (mtd, buf, bd);
/* Prevent the bbt regions from erasing / writing */
mark_bbt_region (mtd, td);
if (md)
mark_bbt_region (mtd, md);
kfree (buf);
return res;
}
/**
* nand_memory_bbt - [GENERIC] create a memory based bad block table
* @mtd: MTD device structure
* @bd: descriptor for the good/bad block search pattern
*
* The function creates a memory based bbt by scanning the device
* for manufacturer / software marked good / bad blocks
*/
static inline int nand_memory_bbt (struct mtd_info *mtd, struct nand_bbt_descr *bd)
{
struct nand_chip *this = mtd->priv;
bd->options &= ~NAND_BBT_SCANEMPTY;
//我们只需要扫描oob data，不需要扫描全部(512+16bytes的数据)
return create_bbt (mtd, this->data_buf, bd, -1);
}
/**
* create_bbt - [GENERIC] Create a bad block table by scanning the device
* @mtd: MTD device structure
* @bu
小弟抽空研究了一下，打算从下到上，在从上到下，分两条主线来研究一下MTD原始设备与FLASH硬件驱动的对话(MTD原始设备与更上层的对话留待以后再研究)。
以下是第一部分，从下到上的介绍FLASH硬件驱动与MTD原始设备是如何建立联系的。
1、首先从入口函数开始：
static int s3c24xx_nand_probe(struct device *dev, int is_s3c2440)
{
struct platform_device *pdev = to_platform_device(dev);
struct s3c2410_platform_nand *plat = to_nand_plat(dev);
//获取nand flash配置用结构体数据(dev.c中定义，详细见附录部分)
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)/n", dev);
info = kmalloc(sizeof(*info), GFP_KERNEL);
if (info == NULL) {
printk(KERN_ERR PFX "no memory for flash info/n");
err = -ENOMEM;
goto exit_error;
}
memzero(info, sizeof(*info));
dev_set_drvdata(dev, info); //以后有用
SPIn_lock_init(&info->controller.lock); //初始化自旋锁
init_waitqueue_head(&info->controller.wq); //初始化等待队列
/* get the clock source and enable it */
info->clk = clk_get(dev, "nand");
if (IS_ERR(info->clk)) {
printk(KERN_ERR PFX "failed to get clock");
err = -ENOENT;
goto exit_error;
}
clk_use(info->clk);
clk_enable(info->clk);
/* allocate and map the resource */
/* currently we assume we have the one resource */
res = pdev->resource; //提取dev.c中定义的与设备相关的资源
size = res->end - res->start + 1;
info->area = request_mem_region(res->start, size, pdev->name);
if (info->area == NULL) {
printk(KERN_ERR PFX "cannot reserve register region/n");
err = -ENOENT;
goto exit_error;
}
info->device = dev;
info->platform = plat; //保存好struct s3c2410_platform_nand结构数据
info->regs = ioremap(res->start, size);//映射nand flash用到的寄存器
info->is_s3c2440 = is_s3c2440;
if (info->regs == NULL) {
printk(KERN_ERR PFX "cannot reserve register region/n");
err = -EIO;
goto exit_error;
}
printk(KERN_INFO PFX "mapped registers at %p/n", info->regs);
/* initialise the hardware */
err = s3c2410_nand_inithw(info, dev);
//初始化s3c2410 nand flash控制，主要是配置S3C2410_nfcONF寄存器
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;
//我的板上只有一块nand flash，配置信息见plat-sets，数目为1。
/* allocate our information */
size = nr_sets * sizeof(*info->mtds);
info->mtds = kmalloc(size, GFP_KERNEL);
if (info->mtds == NULL) {
printk(KERN_ERR PFX "failed to allocate mtd storage/n");
err = -ENOMEM;
goto exit_error;
}
memzero(info->mtds, size);
/* initialise all possible chips */
nmtd = info->mtds;
for (setno = 0; setno < nr_sets; setno++, nmtd++) {
pr_debug("initialising set %d (%p, info %p)/n",
setno, nmtd, info);
s3c2410_nand_init_chip(info, nmtd, sets);
nmtd->scan_res = nand_scan(&nmtd->mtd,
(sets) ? sets->nr_chips : 1);//为什么使用set->nr_chips(还没配置的东西)?
if (nmtd->scan_res == 0) {
s3c2410_nand_add_partition(info, nmtd, sets);
}
if (sets ！= NULL)
sets++;
}
pr_debug("initialised ok/n");
return 0;
exit_error:
s3c2410_nand_remove(dev);
if (err == 0)
err = -EINVAL;
return err;
}
//初始化代表一片flash的struct nand_chip结构
static void s3c2410_nand_init_chip(struct s3c2410_nand_info *info,
struct s3c2410_nand_mtd *nmtd,
struct s3c2410_nand_set *set)
{
struct nand_chip *chip = &nmtd->chip;
chip->IO_ADDR_R = info->regs + S3C2410_NFDATA; //读地址
chip->IO_ADDR_W = info->regs + S3C2410_NFDATA; //写地址
chip->hwcontrol = s3c2410_nand_hwcontrol;
chip->dev_ready = s3c2410_nand_devready; //ready状态查询
chip->write_buf = s3c2410_nand_write_buf; //写函数
chip->read_buf = s3c2410_nand_read_buf; //读函数
chip->select_chip = s3c2410_nand_select_chip; //片选函数
chip->chip_delay = 50;
chip->priv = nmtd;
chip->options = 0;
chip->controller = &info->controller;
if (info->is_s3c2440) {
chip->IO_ADDR_R = info->regs + S3C2440_NFDATA;
chip->IO_ADDR_W = info->regs + S3C2440_NFDATA;
chip->hwcontrol = s3c2440_nand_hwcontrol;
}
nmtd->info = info;
nmtd->mtd.priv = chip;
//nand_scan函数中会调用struct nand_chip *this = mtd->priv取出该struct nand_chip结构
nmtd->set = set;
if (hardware_ecc) {
chip->correct_data = s3c2410_nand_correct_data;
chip->enable_hwecc = s3c2410_nand_enable_hwecc;
chip->calculate_ecc = s3c2410_nand_calculate_ecc;
chip->eccmode = NAND_ECC_HW3_512;
chip->autooob = &nand_hw_eccoob;
if (info->is_s3c2440) {
chip->enable_hwecc = s3c2440_nand_enable_hwecc;
chip->calculate_ecc = s3c2440_nand_calculate_ecc;
}
} else {
chip->eccmode = NAND_ECC_SOFT; //ECC的类型
}
}
/* command and control functions
*
* 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)
{
struct s3c2410_nand_info *info = s3c2410_nand_mtd_toinfo(mtd);
struct nand_chip *chip = mtd->priv;
switch (cmd) {
case NAND_CTL_SETNCE:
case NAND_CTL_CLRNCE:
printk(KERN_ERR "%s: called for NCE/n", __FUNCTION__);
break;
case NAND_CTL_SETCLE:
chip->IO_ADDR_W = info->regs + S3C2410_NFCMD;//写命令
break;
case NAND_CTL_SETALE:
chip->IO_ADDR_W = info->regs + S3C2410_NFADDR;//写地址
break;
/* NAND_CTL_CLRCLE: */
/* NAND_CTL_CLRALE: */
default:
chip->IO_ADDR_W = info->regs + S3C2410_NFDATA;//写数据
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)
{
struct s3c2410_nand_info *info = s3c2410_nand_mtd_toinfo(mtd);
if (info->is_s3c2440)
return readb(info->regs + S3C2440_NFSTAT) & S3C2440_NFSTAT_READY;
return readb(info->regs + S3C2410_NFSTAT) & S3C2410_NFSTAT_BUSY;//返回nand flash都忙标志
}
static void s3c2410_nand_write_buf(struct mtd_info *mtd,
const u_char *buf, int len)
{
struct nand_chip *this = mtd->priv;
writesb(this->IO_ADDR_W, buf, len);//写操作
}
static void s3c2410_nand_read_buf(struct mtd_info *mtd, u_char *buf, int len)
{
struct nand_chip *this = mtd->priv;
reADSb(this->IO_ADDR_R, buf, len);//读操作
}
/* select chip */
/*
* 根据chip都值设置nand flash都片选信号:
* chip = -1 -- 禁用nand flash
* chip ！=-1 -- 选择对应的nand flash
*/
static void s3c2410_nand_select_chip(struct mtd_info *mtd, int chip)
{
struct s3c2410_nand_info *info;
struct s3c2410_nand_mtd *nmtd;
struct nand_chip *this = mtd->priv;
void __iomem *reg;
unsigned long cur;
unsigned long bit;
nmtd = this->priv;
info = nmtd->info;
bit = (info->is_s3c2440) ? S3C2440_NFCONT_nFCE : S3C2410_NFCONF_nFCE;
reg = info->regs+((info->is_s3c2440) ? S3C2440_NFCONT:S3C2410_NFCONF);
cur = readl(reg);
if (chip == -1) {
cur |= bit;
} else {
if (nmtd->set ！= NULL && chip > nmtd->set->nr_chips) {
printk(KERN_ERR PFX "chip %d out of range/n", chip);
return;
}
if (info->platform ！= NULL) {
if (info->platform->select_chip ！= NULL)
(info->platform->select_chip)(nmtd->set, chip);
}
cur &= ~bit;
}
writel(cur, reg);
}
注：
s3c2410_nand_init_chip填充struct nand_chip的一部分成员，nand_scan以通用nand flash的标准进行检测，并填充struct nand_chip的其它成员，必要时根据检测结果进行取舍。
int nand_scan (struct mtd_info *mtd, int maxchips)
{
int i, nand_maf_id, nand_dev_id, busw, maf_id;
struct nand_chip *this = mtd->priv; //取出struct nand_chip结构
/* Get buswidth to select the correct functions*/
busw = this->options & NAND_BUSWIDTH_16; //nand flash的位宽
/* check for proper chip_delay setup, set 20us if not */
if (！this->chip_delay)
this->chip_delay = 20;
/* check, if a user supplied command function given */
if (this->cmdfunc == NULL) //填充命令函数
this->cmdfunc = nand_command;
/* check, if a user supplied wait function given */
if (this->waitfunc == NULL) //填充等待函数
this->waitfunc = nand_wait;
if (！this->select_chip) //s3c2410_nand_init_chip中已定义
this->select_chip = nand_select_chip;
if (！this->write_byte) //使用默认的
this->write_byte = busw ? nand_write_byte16 : nand_write_byte;
if (！this->read_byte) //使用默认的
this->read_byte = busw ? nand_read_byte16 : nand_read_byte;
if (！this->write_word) //使用默认的
this->write_word = nand_write_word;
if (！this->read_word) //使用默认的
this->read_word = nand_read_word;
if (！this->block_bad) //使用默认的
this->block_bad = nand_block_bad;
if (！this->block_markbad) //使用默认的
this->block_markbad = nand_default_block_markbad;
if (！this->write_buf) //s3c2410_nand_init_chip中已定义
this->write_buf = busw ? nand_write_buf16 : nand_write_buf;
if (！this->read_buf) //s3c2410_nand_init_chip中已定义
this->read_buf = busw ? nand_read_buf16 : nand_read_buf;
if (！this->verify_buf) //使用默认的
this->verify_buf = busw ? nand_verify_buf16 : nand_verify_buf;
if (！this->scan_bbt) //使用默认的
this->scan_bbt = nand_default_bbt;
/* Select the device */
this->select_chip(mtd, 0); //片选，可惜在s3c2410 nand flash控制器中此操作为空
/* Send the command for reading device ID */
this->cmdfunc (mtd, NAND_CMD_READID, 0x00, -1);//发送读ID命令
/* Read manufacturer and device IDs */
nand_maf_id = this->read_byte(mtd); //读取生产商ID
nand_dev_id = this->read_byte(mtd); //读取设备ID
/* Print and store flash device information */
for (i = 0; nand_flash_ids.name ！= NULL; i++) {
//保存着nand flash资料的nand_flash_ids表在include/linux/mtd/nand_ids.c文件中，详细见附录
if (nand_dev_id ！= nand_flash_ids.id) //比较设备ID
continue;
if (！mtd->name) mtd->name = nand_flash_ids.name; //填充设备名
this->chipsize = nand_flash_ids.chipsize << 20; //填充设备大小
/* New devices have all the information in additional id bytes */
if (！nand_flash_ids.pagesize) {
int extid;
/* The 3rd id byte contains non relevant data ATM */
extid = this->read_byte(mtd);
/* The 4th id byte is the important one */
extid = this->read_byte(mtd);
/* Calc pagesize */
mtd->oobblock = 1024 << (extid & 0x3);
extid >>= 2;
/* Calc oobsize */
mtd->oobsize = (8 << (extid & 0x03)) * (mtd->oobblock / 512);
extid >>= 2;
/* Calc blocksize. Blocksize is multiples of 64KiB */
mtd->erasesize = (64 * 1024) << (extid & 0x03);
extid >>= 2;
/* Get buswidth information */
busw = (extid & 0x01) ? NAND_BUSWIDTH_16 : 0;
} else {
/* Old devices have this data hardcoded in the
* device id table */
mtd->erasesize = nand_flash_ids.erasesize; //填充檫除单元大小(16k)
mtd->oobblock = nand_flash_ids.pagesize; //填充页大小(512)
mtd->oobsize = mtd->oobblock / 32; //oob大小(512/32=16)
busw = nand_flash_ids.options & NAND_BUSWIDTH_16;//获取nand flash表中定义的位宽
}
/* Try to identify manufacturer */ //比较生产商ID
for (maf_id = 0; nand_manuf_ids[maf_id].id ！= 0x0; maf_id++) {
if (nand_manuf_ids[maf_id].id == nand_maf_id)
break;
}
/* Check, if buswidth is correct. Hardware drivers should set
* this correct ！ */
/用户定义的位宽与芯片实际的位宽不一致，取消nand flash的片选
if (busw ！= (this->options & NAND_BUSWIDTH_16)) {
printk (KERN_INFO "NAND device: Manufacturer ID:"
" 0x%02x, Chip ID: 0x%02x (%s %s)/n", nand_maf_id, nand_dev_id,
nand_manuf_ids[maf_id].name , mtd->name);
printk (KERN_WARNING
"NAND bus width %d instead %d bit/n",
(this->options & NAND_BUSWIDTH_16) ? 16 : 8,
busw ? 16 : 8);
this->select_chip(mtd, -1);//在s3c2410 nand flash控制器驱动中，此操作为空操作
return 1;
}
/* Calculate the address shift fROM the page size */
//计算页、可檫除单元、nand flash大小的偏移值
this->page_shift = ffs(mtd->oobblock) - 1;
this->bbt_erase_shift = this->phys_erase_shift = ffs(mtd->erasesize) - 1;
this->chip_shift = ffs(this->chipsize) - 1;
/* Set the bad block position */
//标注此nand flash为大页还是小页?
this->badblockpos = mtd->oobblock > 512 ?
NAND_LARGE_BADBLOCK_POS : NAND_SMALL_BADBLOCK_POS;
/* Get chip options, preserve non chip based options */
//用户没指定的选项从nand flash表中获取补上
this->options &= ~NAND_CHIPOPTIONS_MSK;
this->options |= nand_flash_ids.options & NAND_CHIPOPTIONS_MSK;
/* Set this as a default. Board drivers can override it, if neccecary */
this->options |= NAND_NO_AUTOINCR;
/* Check if this is a not a samsung device. Do not clear the options
* for chips which are not having an extended id.
*/
if (nand_maf_id ！= NAND_MFR_SAMSUNG && ！nand_flash_ids.pagesize)
this->options &= ~NAND_SAMSUNG_LP_OPTIONS;
/* Check for AND chips with 4 page planes */
if (this->options & NAND_4PAGE_ARRAY)
this->erase_cmd = multi_erase_cmd;
else
this->erase_cmd = single_erase_cmd;
/* Do not replace user supplied command function ！ */
if (mtd->oobblock > 512 && this->cmdfunc == nand_command)
this->cmdfunc = nand_command_lp;
printk (KERN_INFO "NAND device: Manufacturer ID:"
" 0x%02x, Chip ID: 0x%02x (%s %s)/n", nand_maf_id, nand_dev_id,
nand_manuf_ids[maf_id].name , nand_flash_ids.name);
break;
}//好的，检测结束^_^
if (！nand_flash_ids.name) {
printk (KERN_WARNING "No NAND device found！/n");
this->select_chip(mtd, -1);
return 1;
}
//统计一下同种类型的nand flash有多少块(我板上只有一块)
for (i=1; i < maxchips; i++) {
this->select_chip(mtd, i);
/* Send the command for reading device ID */
this->cmdfunc (mtd, NAND_CMD_READID, 0x00, -1);
/* Read manufacturer and device IDs */
if (nand_maf_id ！= this->read_byte(mtd) ||
nand_dev_id ！= this->read_byte(mtd))
break;
}
if (i > 1)
printk(KERN_INFO "%d NAND chips detected/n", i);
/* Allocate buffers, if neccecary */
if (！this->oob_buf) {
size_t len;
//求出一个檫除单元64K中oob所占用的总空间
len = mtd->oobsize << (this->phys_erase_shift - this->page_shift);
this->oob_buf = kmalloc (len, GFP_KERNEL);
if (！this->oob_buf) {
printk (KERN_ERR "nand_scan(): Cannot allocate oob_buf/n");
return -ENOMEM;
}
this->options |= NAND_OOBBUF_ALLOC;//oob空间已分配，置相应的标志位
}
if (！this->data_buf) {
size_t len;
len = mtd->oobblock + mtd->oobsize;//512+16=128
this->data_buf = kmalloc (len, GFP_KERNEL);
if (！this->data_buf) {
if (this->options & NAND_OOBBUF_ALLOC)
kfree (this->oob_buf);
printk (KERN_ERR "nand_scan(): Cannot allocate data_buf/n");
return -ENOMEM;
}
this->options |= NAND_DATABUF_ALLOC;//数据空间已分配，置相应的标志位
}
/* Store the number of chips and calc total size for mtd */
this->numchips = i;//记录nand flash片数
mtd->size = i * this->chipsize;//计算出nand flash总大小
/* Convert chipsize to number of pages per chip -1. */
this->pagemask = (this->chipsize >> this->page_shift) - 1;//(64M>>9)-1=128k-1=0x1ffff
/* Preset the internal oob buffer */
//oob_buf全部置为0xff
mEMSet(this->oob_buf, 0xff, mtd->oobsize << (this->phys_erase_shift - this->page_shift));
/* If no default placement scheme is given, select an
* appropriate one */
if (！this->autooob) { //我们选用的是NAND_ECC_SOFT，autooob未设置
/* Select the appropriate default oob placement scheme for
* placement agnostic filesystems */
switch (mtd->oobsize) {
case 8:
this->autooob = &nand_oob_8;
break;
case 16:
this->autooob = &nand_oob_16;//我们的nand flash属于这一类
break;
case 64:
this->autooob = &nand_oob_64;
break;
default:
printk (KERN_WARNING "No oob scheme defined for oobsize %d/n",
mtd->oobsize);
BUG();
}
}
注：
ECC的东西不是很懂，先跳过^_^
/* The number of bytes available for the filesystem to place fs dependend
* oob data */
mtd->oobavail = 0;
for (i = 0; this->autooob->oobfree[1]; i++)
mtd->oobavail += this->autooob->oobfree[1];
/*
* check ECC mode, default to software
* if 3byte/512byte hardware ECC is selected and we have 256 byte pagesize
* fallback to software ECC
*/
this->eccsize = 256; /* set default eccsize */
this->eccbytes = 3;
switch (this->eccmode) {
case NAND_ECC_HW12_2048:
if (mtd->oobblock < 2048) {
printk(KERN_WARNING "2048 byte HW ECC not possible on %d byte page size, fallback to SW ECC/n",
mtd->oobblock);
this->eccmode = NAND_ECC_SOFT;
this->calculate_ecc = nand_calculate_ecc;
this->correct_data = nand_correct_data;
} else
this->eccsize = 2048;
break;
case NAND_ECC_HW3_512:
case NAND_ECC_HW6_512:
case NAND_ECC_HW8_512:
if (mtd->oobblock == 256) {
printk (KERN_WARNING "512 byte HW ECC not possible on 256 Byte pagesize, fallback to SW ECC /n");
this->eccmode = NAND_ECC_SOFT;
this->calculate_ecc = nand_calculate_ecc;
this->correct_data = nand_correct_data;
} else
this->eccsize = 512; /* set eccsize to 512 */
break;
case NAND_ECC_HW3_256:
break;
case NAND_ECC_NONE:
printk (KERN_WARNING "NAND_ECC_NONE selected by board driver. This is not recommended ！/n");
this->eccmode = NAND_ECC_NONE;
break;
case NAND_ECC_SOFT:
this->calculate_ecc = nand_calculate_ecc;
this->correct_data = nand_correct_data;
break;
default:
printk (KERN_WARNING "Invalid NAND_ECC_MODE %d/n", this->eccmode);
BUG();
}
/* Check hardware ecc function availability and adjust number of ecc bytes per
* calculation step
*/
switch (this->eccmode) {
case NAND_ECC_HW12_2048:
this->eccbytes += 4;
case NAND_ECC_HW8_512:
this->eccbytes += 2;
case NAND_ECC_HW6_512:
this->eccbytes += 3;
case NAND_ECC_HW3_512:
case NAND_ECC_HW3_256:
if (this->calculate_ecc && this->correct_data && this->enable_hwecc)
break;
printk (KERN_WARNING "No ECC functions supplied, Hardware ECC not possible/n");
BUG();
}
mtd->eccsize = this->eccsize;
/* Set the number of read / write steps for one page to ensure ECC generation */
switch (this->eccmode) {
case NAND_ECC_HW12_2048:
this->eccsteps = mtd->oobblock / 2048;
break;
case NAND_ECC_HW3_512:
case NAND_ECC_HW6_512:
case NAND_ECC_HW8_512:
this->eccsteps = mtd->oobblock / 512;
break;
case NAND_ECC_HW3_256:
case NAND_ECC_SOFT:
this->eccsteps = mtd->oobblock / 256;
break;
case NAND_ECC_NONE:
this->eccsteps = 1;
break;
}
/* Initialize state, waitqueue and spinlock */
this->state = FL_READY;
init_waitqueue_head (&this->wq);
spin_lock_init (&this->chip_lock);
/* De-select the device */
this->select_chip(mtd, -1);
/* Invalidate the pagebuffer reference */
this->pagebuf = -1;
/* Fill in remaining MTD driver data */
//填充mtd结构的其它部分
mtd->type = MTD_NANDFLASH;
mtd->flags = MTD_CAP_NANDFLASH | MTD_ECC;
mtd->ecctype = MTD_ECC_SW;
mtd->erase = nand_erase;
mtd->point = NULL;
mtd->unpoint = NULL;
mtd->read = nand_read;
/* nand_read->nand_do_read_ecc->read_buf->s3c2410_nand_read_buf */
mtd->write = nand_write;
/* nand_write->nand_write_ecc->nand_write_page->write_buf->s3c2410_nand_write_buf */
mtd->read_ecc = nand_read_ecc;
mtd->write_ecc = nand_write_ecc;
mtd->read_oob = nand_read_oob;
mtd->write_oob = nand_write_oob;
mtd->readv = NULL;
mtd->writev = nand_writev;
mtd->writev_ecc = nand_writev_ecc;
mtd->sync = nand_sync;
mtd->lock = NULL;
mtd->unlock = NULL;
mtd->suspend = NULL;
mtd->resume = NULL;
mtd->block_isbad = nand_block_isbad;
mtd->block_markbad = nand_block_markbad;
/* and make the autooob the default one */
meMCPy(&mtd->oobinfo, this->autooob, sizeof(mtd->oobinfo));
mtd->owner = THIS_MODULE;
/* Check, if we should skip the bad block table scan */
if (this->options & NAND_SKIP_BBTSCAN)
return 0;
/* Build bad block table */
return this->scan_bbt (mtd);
}
/**
* nand_command - [DEFAULT] Send command to NAND device
* @mtd: MTD device structure
* @command: the command to be sent
* @column: the column address for this command, -1 if none
* @page_addr: the page address for this command, -1 if none
*
* Send command to NAND device. This function is used for small page
* devices (256/512 Bytes per page)
*/
static void nand_command (struct mtd_info *mtd, unsigned command, int column, int page_addr)
{
register struct nand_chip *this = mtd->priv;
/* Begin command latch cycle */
this->hwcontrol(mtd, NAND_CTL_SETCLE); //选择写入S3C2410_NFCMD寄存器
/*
* Write out the command to the device.
*/
if (command == NAND_CMD_SEQIN) {
int reADCmd;
if (column >= mtd->oobblock) { //读/写位置超出512，读oob_data
/* OOB area */
column -= mtd->oobblock;
readcmd = NAND_CMD_READOOB;
} else if (column < 256) { //读/写位置在前512，使用read0命令
/* First 256 bytes --> READ0 */
readcmd = NAND_CMD_READ0;
} else { //读/写位置在后512，使用read1命令
column -= 256;
readcmd = NAND_CMD_READ1;
}
this->write_byte(mtd, readcmd); //写入具体命令
}
this->write_byte(mtd, command);
/* Set ALE and clear CLE to start address cycle */
/* 清楚CLE，锁存命令；置位ALE，开始传输地址 */
this->hwcontrol(mtd, NAND_CTL_CLRCLE); //锁存命令
if (column ！= -1 || page_addr ！= -1) {
this->hwcontrol(mtd, NAND_CTL_SETALE); //选择写入S3C2410_NFADDR寄存器
/* Serially input address */
if (column ！= -1) {
/* Adjust columns for 16 bit buswidth */
if (this->options & NAND_BUSWIDTH_16)
column >>= 1;
this->write_byte(mtd, column); //写入列地址
}
if (page_addr ！= -1) { //写入页地址(分三个字节写入)
this->write_byte(mtd, (unsigned char) (page_addr & 0xff));
this->write_byte(mtd, (unsigned char) ((page_addr >> 8) & 0xff));
/* One more address cycle for devices > 32MiB */
if (this->chipsize > (32 << 20))
this->write_byte(mtd, (unsigned char) ((page_addr >> 16) & 0x0f));
}
/* Latch in address */
/* 锁存地址 */
this->hwcontrol(mtd, NAND_CTL_CLRALE);
}
/*
* program and erase have their own busy handlers
* status and sequential in needs no delay
*/
switch (command) {
case NAND_CMD_PAGEPROG:
case NAND_CMD_ERASE1:
case NAND_CMD_ERASE2:
case NAND_CMD_SEQIN:
case NAND_CMD_STATUS:
return;
case NAND_CMD_RESET: //复位操作
// 等待nand flash become ready
if (this->dev_ready) //判断nand flash 是否busy(1:ready 0:busy)
break;
udelay(this->chip_delay);
this->hwcontrol(mtd, NAND_CTL_SETCLE);
this->write_byte(mtd, NAND_CMD_STATUS);
this->hwcontrol(mtd, NAND_CTL_CLRCLE);
while ( ！(this->read_byte(mtd) & NAND_STATUS_READY));
return;
/* This applies to read commands */
default:
/*
* If we don't have access to the busy pin, we apply the given
* command delay
*/
if (！this->dev_ready) {
udelay (this->chip_delay);//稍作延迟
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 for the ready pin, after a command
* The timeout is catched later.
*/
static void nand_wait_ready(struct mtd_info *mtd)
{
struct nand_chip *this = mtd->priv;
unsigned long timeo = jiffies + 2;
/* wait until command is processed or timeout occures */
do {
if (this->dev_ready(mtd)) //简单调用this->dev_ready(s3c2410_nand_devready)函数 等待nand flash become ready
return;
touch_softlockup_watchdog();
} while (time_before(jiffies, timeo));
}
/**
* nand_wait - [DEFAULT] wait until the command is done
* @mtd: MTD device structure
* @this: NAND chip structure
* @state: state to select the max. timeout value
*
* Wait for command done. This applies to erase and program only
* Erase can take up to 400ms and program up to 20ms according to
* general NAND and SmartMedia specs
*
*/
/* 等待知道命令传输完成，适用于檫除和写入命令 */
static int nand_wait(struct mtd_info *mtd, struct nand_chip *this, int state)
{
unsigned long timeo = jiffies;
int status;
if (state == FL_ERASING)
timeo += (HZ * 400) / 1000;//檫除操作的话，时间相对要长一些
else
timeo += (HZ * 20) / 1000;
/* Apply this short delay always to ensure that we do wait tWB in
* any case on any machine. */
ndelay (100);
if ((state == FL_ERASING) && (this->options & NAND_IS_AND))
this->cmdfunc (mtd, NAND_CMD_STATUS_MULTI, -1, -1);
else
this->cmdfunc (mtd, NAND_CMD_STATUS, -1, -1);
while (time_before(jiffies, timeo)) {
/* Check, if we were interrupted */
if (this->state ！= state)
return 0;
/* 等待nand flash become ready */
if (this->dev_ready) {
if (this->dev_ready(mtd))
break;
} else {
if (this->read_byte(mtd) & NAND_STATUS_READY)
break;
}
cond_resched();
}
status = (int) this->read_byte(mtd);
return status;
}
/**
* nand_block_bad - [DEFAULT] Read bad block marker from the chip
* 检查nand flash中某一页是否为坏块
* @mtd: MTD device structure
* @ofs: offset from device start
* @getchip: 0, if the chip is already selected
*
* Check, if the block is bad.
*/
static int nand_block_bad(struct mtd_info *mtd, loff_t ofs, int getchip)
{
int page, chipnr, res = 0;
struct nand_chip *this = mtd->priv;
u16 bad;
if (getchip) {
page = (int)(ofs >> this->page_shift);
chipnr = (int)(ofs >> this->chip_shift);
/* Grab the lock and see if the device is available */
nand_get_device (this, mtd, FL_READING);
/* Select the NAND device */
this->select_chip(mtd, chipnr);
} else
page = (int) ofs;
if (this->options & NAND_BUSWIDTH_16) {
this->cmdfunc (mtd, NAND_CMD_READOOB, this->badblockpos & 0xFE, page & this->pagemask);
bad = cpu_to_le16(this->read_word(mtd));
if (this->badblockpos & 0x1)
bad >>= 1;
if ((bad & 0xFF) ！= 0xff)
res = 1;
} else {
this->cmdfunc (mtd, NAND_CMD_READOOB, this->badblockpos, page & this->pagemask);
/* 发送读oob_data命令(oob_data的badblockpos (第6)位记录着坏块标志) */
if (this->read_byte(mtd) ！= 0xff)//坏块
res = 1;
}
if (getchip) {
/* Deselect and wake up anyone waiting on the device */
nand_release_device(mtd);
}
return res;
}
/**
* nand_default_block_markbad - [DEFAULT] mark a block bad
* 标志坏块
* @mtd: MTD device structure
* @ofs: offset from device start
*
* This is the default implementation, which can be overridden by
* a hardware specific driver.
*/
static int nand_default_block_markbad(struct mtd_info *mtd, loff_t ofs)
{
struct nand_chip *this = mtd->priv;
u_char buf[2] = {0, 0};
size_t retlen;
int block;
/* Get block number */
block = ((int) ofs) >> this->bbt_erase_shift;
if (this->bbt)
this->bbt[block >> 2] |= 0x01 << ((block & 0x03) << 1);
/*
这个暂时不是很好说：内核维护一个标志bad block表，使用2bit来表示1block。
这个表在开机的时候通过扫描nand flash每个block的头两页的oob数据来生成，
发现坏块后至相应的block标志位为非零(有时候至3，但有时候至1，还没搞明白有什么不同)
*/
/* Do we have a flash based bad block table ? */
if (this->options & NAND_USE_FLASH_BBT)//samsun nand flash不属于这种，暂时不去研究，以后同
return nand_update_bbt (mtd, ofs);
/* We write two bytes, so we dont have to mess with 16 bit access */
ofs += mtd->oobsize + (this->badblockpos & ~0x01);//?
return nand_write_oob (mtd, ofs , 2, &retlen, buf);
}
/**
* nand_verify_buf - [DEFAULT] Verify chip data against buffer
* 检验nand flash与buffer的数据是否一致
* @mtd: MTD device structure
* @buf: buffer containing the data to compare
* @len: number of bytes to compare
*
* Default verify function for 8bit buswith
*/
static int nand_verify_buf(struct mtd_info *mtd, const u_char *buf, int len)
{
int i;
struct nand_chip *this = mtd->priv;
for (i=0; i<len; i++)
if (buf ！= readb(this->IO_ADDR_R))
return -EFAULT;
return 0;
}
/**
* nand_default_bbt - [NAND Interface] Select a default bad block table for the device
* @mtd: MTD device structure
*
* This function selects the default bad block table
* support for the device and calls the nand_scan_bbt function
*
*/
int nand_default_bbt (struct mtd_info *mtd)
{
struct nand_chip *this = mtd->priv;
/* Default for AG-AND. We must use a flash based
* bad block table as the devices have factory marked
* _good_ blocks. Erasing those blocks leads to loss
* of the good / bad information, so we _must_ store
* this information in a good / bad table during
* startup
*/
if (this->options & NAND_IS_AND) {
/* Use the default pattern descriptors */
if (！this->bbt_td) {
this->bbt_td = &bbt_main_descr;
this->bbt_md = &bbt_mirror_descr;
}
this->options |= NAND_USE_FLASH_BBT;
return nand_scan_bbt (mtd, &agand_flashbased);
}
/* Is a flash based bad block table requested ? */
if (this->options & NAND_USE_FLASH_BBT) {
/* Use the default pattern descriptors */
if (！this->bbt_td) {
this->bbt_td = &bbt_main_descr;
this->bbt_md = &bbt_mirror_descr;
}
if (！this->badblock_pattern) {
this->badblock_pattern = (mtd->oobblock > 512) ?
&largepage_flashbased : &smallpage_flashbased;
}
} else { //samsun nand flash的坏块表不存在与nand flash里面，需要扫描来生成。
this->bbt_td = NULL;
this->bbt_md = NULL;
if (！this->badblock_pattern) {
this->badblock_pattern = (mtd->oobblock > 512) ?
&largepage_memorybased : &smallpage_memorybased;
}
}
return nand_scan_bbt (mtd, this->badblock_pattern);
}
/**
* nand_scan_bbt - [NAND Interface] scan, find, read and maybe create bad block table(s)
* @mtd: MTD device structure
* @bd: descriptor for the good/bad block search pattern
*
* The function checks, if a bad block table(s) is/are already
* available. If not it scans the device for manufacturer
* marked good / bad blocks and writes the bad block table(s) to
* the selected place.
*
* The bad block table memory is allocated here. It must be freed
* by calling the nand_free_bbt function.
*
*/
int nand_scan_bbt (struct mtd_info *mtd, struct nand_bbt_descr *bd)
{
struct nand_chip *this = mtd->priv;
int len, res = 0;
uint8_t *buf;
struct nand_bbt_descr *td = this->bbt_td;
struct nand_bbt_descr *md = this->bbt_md;
len = mtd->size >> (this->bbt_erase_shift + 2);
/* Allocate memory (2bit per block) */
/* 2bit per block=(2/8)byte per block，所以上面要多右移2位 */
this->bbt = kmalloc (len, GFP_KERNEL);
if (！this->bbt) {
printk (KERN_ERR "nand_scan_bbt: Out of memory/n");
return -ENOMEM;
}
/* Clear the memory bad block table */
memset (this->bbt, 0x00, len);
/* If no primary table decriptor is given, scan the device
* to build a memory based bad block table
*/
if (！td) {
if ((res = nand_memory_bbt(mtd, bd))) {
printk (KERN_ERR "nand_bbt: Can't scan flash and build the RAM-based BBT/n");
kfree (this->bbt);
this->bbt = NULL;
}
return res;
}
/* Allocate a temporary buffer for one eraseblock incl. oob */
/* 分配1 block所需要的oob data空间 */
len = (1 << this->bbt_erase_shift);
len += (len >> this->page_shift) * mtd->oobsize;
buf = kmalloc (len, GFP_KERNEL);
if (！buf) {
printk (KERN_ERR "nand_bbt: Out of memory/n");
kfree (this->bbt);
this->bbt = NULL;
return -ENOMEM;
}
//由于td、md均为NULL，一下函数基本不起作用，先不去研究它
/* Is the bbt at a given page ? */
if (td->options & NAND_BBT_ABSPAGE) {
res = read_abs_bbts (mtd, buf, td, md);
} else {
/* Search the bad block table using a pattern in oob */
res = search_read_bbts (mtd, buf, td, md);
}
if (res)
res = check_create (mtd, buf, bd);
/* Prevent the bbt regions from erasing / writing */
mark_bbt_region (mtd, td);
if (md)
mark_bbt_region (mtd, md);
kfree (buf);
return res;
}
/**
* nand_memory_bbt - [GENERIC] create a memory based bad block table
* @mtd: MTD device structure
* @bd: descriptor for the good/bad block search pattern
*
* The function creates a memory based bbt by scanning the device
* for manufacturer / software marked good / bad blocks
*/
static inline int nand_memory_bbt (struct mtd_info *mtd, struct nand_bbt_descr *bd)
{
struct nand_chip *this = mtd->priv;
bd->options &= ~NAND_BBT_SCANEMPTY;
//我们只需要扫描oob data，不需要扫描全部(512+16bytes的数据)
return create_bbt (mtd, this->data_buf, bd, -1);
}
/**
* create_bbt - [GENERIC] Create a bad block table by scanning the device
* @mtd: MTD device structure
* @bu