s3c2416--nandflash驱动--八位ecc校验
环境：
kerner:linux-2.6.39
uboot:u-boot-1.3.4
1.根据上篇
s3c2146 nandflash 8 bit ECC校验
我们知道了怎么配置和纠正ecc的大概想法。
2.我们可以参考u-boot-1.3.4目录的cpu/s3c24xx/nand.c关于8位ecc的使能，计算ecc，校准ecc。
使能函数：void s3c_nand_enable_hwecc_8bit(struct mtd_info *mtd, int mode)
计算ecc函数：int s3c_nand_calculate_ecc_8bit(struct mtd_info *mtd, const u_char *dat, u_char *ecc_code)
校准ecc函数：int s3c_nand_correct_data_8bit(struct mtd_info *mtd, u_char *dat, u_char *read_ecc, u_char *calc_ecc)
具体的内容请查看uboot中的源码。
3.修改我们的linux-2.6.39中的nand驱动源码目录是：drivers/mtd/nand/s3c2410.c
修改ecc纠错的位数只涉及到三个函数以及两个结构体分别是：
（1）配置校准的快大小和oob区需要的ecc字节数
注：注释的是本次跟改过的关于八位ecc的代码：注释的文字用红色表示。
/**
* s3c2410_nand_update_chip - post probe update
* @info: The controller instance.
* @nmtd: The driver version of the MTD instance.
*
* This routine is called after the chip probe has successfully completed
* and the relevant per-chip information updated. This call ensure that
* we update the internal state accordingly.
*
* The internal state is currently limited to the ECC state information.
*/
static void s3c2410_nand_update_chip(struct s3c2410_nand_info *info,
struct s3c2410_nand_mtd *nmtd)
{
struct nand_chip *chip = &nmtd->chip;
dev_dbg(info->device, "chip %p => page shift %d\n",
chip, chip->page_shift);
if (chip->ecc.mode != NAND_ECC_HW) 我们选择的是硬件ecc（所以必须先配置为硬件ecc）(make menuconfig->Device Drivers-> <*> Memory Technology Device (MTD) support ---> <*> NAND Device Support ---> <*> NAND Flash support for Samsung S3C SoCs 和[*] Samsung S3C NAND Hardware ECC )
return;
/* change the behaviour depending on wether we are using
* the large or small page nand device */
if (chip->page_shift > 10) {
chip->ecc.size = 512; 因为是8位ecc所以只能512bytes,根据s3c2416数据手册（chip->ecc.size:能检测的ecc大小）
chip->ecc.bytes = 13; 根据s3c2416的数据手册当是8位ecc时，根据这个寄存器得到这个值NFM8ECC0 ,NFM8ECC1,NFM8ECC2,NFM8ECC3（chip->ecc.bytes:所产生的ecc字节数用于存在oob区（spare区））
chip->ecc.layout = &nand_hw_eccoob; //oob关于产生的ecc的布局
} else {
chip->ecc.size = 512;
chip->ecc.bytes = 4;
chip->ecc.layout = &nand_hw_eccoob;
}
}
2.配置oob区的布局
/* new oob placement block for use with hardware ecc generation
*/
static struct nand_ecclayout nand_hw_eccoob = {
.eccbytes = 13*4, 我们flash是一块2k+64bytes（这个可以查flash的手册，也可以在uboot启动的时候用命令 nand info得到信息，因为512bytes产生13个字节的ecc，所以一块等于13*4）
.eccpos = {11, 12, 13, 14, 15,
16, 17, 18, 19, 20,
21, 22, 23, 24, 25, 26, 27, 28, 29, 30,
31, 32, 33, 34, 35, 36, 37, 38, 39, 40,
41, 42, 43, 44, 45, 46, 47, 48, 49, 50,
51, 52, 53, 54, 55, 56, 57, 58, 59, 60,
61, 62
}, 布局随意只要有52个字节即可
.oobfree = {{2, 9}, {63, 2}} oob空闲的字节数 （64-52=12）,（0,1两个字节用于存放bad快标志）{(2,9):表示2到10九个字节空间}
};
/* controller and mtd information */
3.使能8位Ecc(因为2416用的是这个函数)
static void s3c2412_nand_enable_hwecc(struct mtd_info *mtd, int mode)
{
struct s3c2410_nand_info *info = s3c2410_nand_mtd_toinfo(mtd);
unsigned long ctrl;
cur_ecc_mode = mode; //知道当前的模式是读还是写flash
unsigned long msgLength = 0;
msgLength = readl(info->regs + S3C2410_NFCONF); ///根据s3c2416数据手册
（1）使用8位ECC校验，首先将MsgLength位设置为0（设置message数据长度为512字节），同时ECCType位设置为“01”（使能8位ECC校验）。每读512字节数据，8位ECC校验模块就会产生ECC校验码。为了初始化8位ECC校验模块，首先要将MainECCLock（NFCONT[7]）清零，然后向InitMECC（NFCONT[5]）位写1。
MainECCLock位决定了ECC校验码是否产生。
NOTE：在8位ECC校验中，应该先清除MainECCLock位，再清除InitMECC位msgLength &= ~(1<<25);
writel(msgLength, info->regs + S3C2410_NFCONF);
unsigned long initEccBit = 0;
initEccBit = readl(info->regs + S3C2410_NFCONF);
initEccBit &= ~(1<<24);
initEccBit |= 1<<23;
writel(initEccBit, info->regs + S3C2410_NFCONF);
ctrl = readl(info->regs + S3C2440_NFCONT);
ctrl &= ~S3C2412_NFCONT_MAIN_ECC_LOCK;
writel(ctrl, info->regs + S3C2440_NFCONT);
ctrl = readl(info->regs + S3C2440_NFCONT);
ctrl |= S3C2412_NFCONT_INIT_MAIN_ECC;
writel(ctrl, info->regs + S3C2440_NFCONT);
ctrl = readl(info->regs + S3C2440_NFCONT);
if (NAND_ECC_WRITE == mode)
ctrl &= ~(S3C2412_NFCONT_ECC4_DIRWR); //使能4-bit, 8-bitECC encoding / decoding control 0
//0 = Decoding 4-bit, 8bit ECC, It is used for page read（好像反了）
//1 = Encoding 4-bit, 8-bit ECC, It is be used for page program
else
ctrl |= (S3C2412_NFCONT_ECC4_DIRWR);
writel(ctrl, info->regs + S3C2440_NFCONT);
}
4.计算8位Ecc(因为2416用的是这个函数)
static int s3c2412_nand_calculate_ecc(struct mtd_info *mtd, const u_char *dat, u_char *ecc_code)
{
struct s3c2410_nand_info *info = s3c2410_nand_mtd_toinfo(mtd);
/** ytq----------2016-09-19----------------------start*/
unsigned long ctrl;
unsigned long nfm8ecc0 = 0, nfm8ecc1 = 0, nfm8ecc2 = 0, nfm8ecc3 = 0;
unsigned long nEccDirect = 0;
/**
在读取512字节数据之后（不包括spare区数据），你必须把MainECCLock位设置为“1”（禁止产生ECC）并读取NANDFlash中保存的针对此512字节数据的ECC校验值
*/
ctrl = readl(info->regs + S3C2440_NFCONT);
ctrl |= S3C2412_NFCONT_MAIN_ECC_LOCK;
writel(ctrl, info->regs + S3C2440_NFCONT);
if (cur_ecc_mode == NAND_ECC_READ)
{
/*When ECCDecDone (NFSTAT[6]) is set (‘1’), NFECCERR0 indicates whether error bit exist or not. If any
error exists, you can fix it by referencing NFECCERR0/1 and NFMLCBITPT registe*/
while (!(readl(info->regs + S3C2412_NFSTAT) & S3C2412_NFSTAT_ECC_DECDONE)) {}
}
else
{
/*根据数据手册--在写入了512字节数据之后（不包括spare区数据），ECC校验码就会自动更新到寄存器NF8MECC0, NFMECC1, NFMECC2, NFMECC3中。如果你使用的NAND flash一页只有512字节数据，那么你就可以将产生的ECC校验码立即写入对应的spare区。如果你使用的NAND flash一页为2k或者4k， 那么只能先将ECC校验码存到内存里（可以建立一个数组）。等到将整页的数据完全写完后，再将保存在内存里的ECC校验码写入对应的spare区。
/*
while (!(readl(info->regs + S3C2412_NFSTAT) & (S3C2412_NFSTAT_ECC_ENCDONE))) {}
nfm8ecc0 = readl(info->regs + S3C2412_NFM8ECC0);
ecc_code[0] = (nfm8ecc0 & 0xff);
ecc_code[1] = ((nfm8ecc0 >> 8) & 0xff);
ecc_code[2] = ((nfm8ecc0 >> 16) & 0xff);
ecc_code[3] = ((nfm8ecc0 >> 24) & 0xff);
nfm8ecc1 = readl(info->regs + S3C2412_NFM8ECC1);
ecc_code[4] = (nfm8ecc1 & 0xff);
ecc_code[5] = ((nfm8ecc1 >> 8) & 0xff);
ecc_code[6] = ((nfm8ecc1 >> 16) & 0xff);
ecc_code[7] = ((nfm8ecc1 >> 24) & 0xff);
nfm8ecc2 = readl(info->regs + S3C2412_NFM8ECC2);
ecc_code[8] = (nfm8ecc2 & 0xff);
ecc_code[9] = ((nfm8ecc2 >> 8) & 0xff);
ecc_code[10] = ((nfm8ecc2 >> 16) & 0xff);
ecc_code[11] = ((nfm8ecc2 >> 24) & 0xff);
nfm8ecc3 = readl(info->regs + S3C2412_NFM8ECC3);
ecc_code[12] = (nfm8ecc3 & 0xff);
}
return 0;
}
5.校准8位Ecc(因为2416用的是这个函数)
static int s3c2410_nand_correct_data(struct mtd_info *mtd, u_char *dat,
u_char *read_ecc, u_char *calc_ecc)
{
struct s3c2410_nand_info *info = s3c2410_nand_mtd_toinfo(mtd);
unsigned long nErrType = 0;
unsigned long nErrByte = 0;
unsigned long nErrBitPat = 0;
unsigned long nEccDecodeDone = 0;
unsigned long nEccDecodeDone1 = 0;
unsigned long nf8eccerr0, nf8eccerr1, nf8eccerr2;
unsigned long nfmlc8bitpt0, nfmlc8bitpt1;
int ret = -1;
/*Indicates the 4-bit ECC decoding engine is searching whether a error exists or not Initial State 0 0 = Idle 1 = Busy*/
while (readl(info->regs +S3C2412_NF8ECC_ERR0) & (1<<31)) {}
/*当ECCDecDone位被置为“1”时， NF8ECCERR0寄存器能够表明是否存在错误。如果错误存在，你可以通过寄存器NF8ECCERR0/1/2 和 NFMLCBITPT0/1 的值来矫正这些错误。*/
nf8eccerr0 = readl(info->regs + S3C2412_NF8ECC_ERR0);
nf8eccerr1 = readl(info->regs + S3C2412_NF8ECC_ERR1);
nf8eccerr2 = readl(info->regs + S3C2412_NF8ECC_ERR2);
nfmlc8bitpt0 = readl(info->regs + S3C2412_NFMLC8BIT_PT0);
nfmlc8bitpt1 = readl(info->regs + S3C2412_NFMLC8BIT_PT1);
nErrType = ((nf8eccerr0 >> 25) & 0xf); //根据数据手册判断出现几位错误
if((nf8eccerr0 >> 29) & 0x1)
nErrType = 0;
switch(nErrType)
{
case 9:
ret = -1;
printk("s3c-nand: ECC uncorrectable error detected\n");
break;
case 8:
dat[((nf8eccerr2 >> 22) & 0x3ff)] ^= ((nfmlc8bitpt1 >> 24) & 0xff);
case 7:
dat[((nf8eccerr2 >> 11) & 0x3ff)] ^= ((nfmlc8bitpt1 >> 16) & 0xff);
case 6:
dat[(nf8eccerr2 & 0x3ff)] ^= ((nfmlc8bitpt1 >> 8) & 0xff);
case 5:
dat[((nf8eccerr1 >> 22) & 0x3ff)] ^= (nfmlc8bitpt1 & 0xff);
case 4:
dat[((nf8eccerr1 >> 11) & 0x3ff)] ^= ((nfmlc8bitpt0 >> 24) & 0xff);
case 3:
dat[(nf8eccerr1 & 0x3ff)] ^= ((nfmlc8bitpt0 >> 16) & 0xff);
case 2:
dat[((nf8eccerr0 >> 15) & 0x3ff)] ^= ((nfmlc8bitpt0 >> 8) & 0xff);
case 1:
printk("s3c-nand: %d bit(s) error detected, corrected successfully\n", nErrType);
dat[(nf8eccerr0 & 0x3ff)] ^= (nfmlc8bitpt0 & 0xff);
ret = nErrType;
break;
case 0:
ret = 0;
break;
}
return ret;
}