Commit a2593247 authored by Ben Dooks's avatar Ben Dooks Committed by David Woodhouse

[MTD] [NAND] S3C2410: Hardware ECC correction code

Add support for correcting errors detected by the
hardware ECC.
Signed-off-by: default avatarBen Dooks <ben-linux@fluff.org>
Signed-off-by: default avatarDavid Woodhouse <dwmw2@infradead.org>
parent a7a6ace1
...@@ -126,10 +126,6 @@ config MTD_NAND_S3C2410_HWECC ...@@ -126,10 +126,6 @@ config MTD_NAND_S3C2410_HWECC
incorrect ECC generation, and if using these, the default of incorrect ECC generation, and if using these, the default of
software ECC is preferable. software ECC is preferable.
If you lay down a device with the hardware ECC, then you will
currently not be able to switch to software, as there is no
implementation for ECC method used by the S3C2410
config MTD_NAND_NDFC config MTD_NAND_NDFC
tristate "NDFC NanD Flash Controller" tristate "NDFC NanD Flash Controller"
depends on MTD_NAND && 44x depends on MTD_NAND && 44x
......
...@@ -337,17 +337,69 @@ static int s3c2412_nand_devready(struct mtd_info *mtd) ...@@ -337,17 +337,69 @@ static int s3c2412_nand_devready(struct mtd_info *mtd)
static int s3c2410_nand_correct_data(struct mtd_info *mtd, u_char *dat, static int s3c2410_nand_correct_data(struct mtd_info *mtd, u_char *dat,
u_char *read_ecc, u_char *calc_ecc) u_char *read_ecc, u_char *calc_ecc)
{ {
pr_debug("s3c2410_nand_correct_data(%p,%p,%p,%p)\n", mtd, dat, read_ecc, calc_ecc); struct s3c2410_nand_info *info = s3c2410_nand_mtd_toinfo(mtd);
unsigned int diff0, diff1, diff2;
unsigned int bit, byte;
pr_debug("eccs: read %02x,%02x,%02x vs calc %02x,%02x,%02x\n", pr_debug("%s(%p,%p,%p,%p)\n", __func__, mtd, dat, read_ecc, calc_ecc);
read_ecc[0], read_ecc[1], read_ecc[2], calc_ecc[0], calc_ecc[1], calc_ecc[2]);
if (read_ecc[0] == calc_ecc[0] && read_ecc[1] == calc_ecc[1] && read_ecc[2] == calc_ecc[2]) diff0 = read_ecc[0] ^ calc_ecc[0];
return 0; diff1 = read_ecc[1] ^ calc_ecc[1];
diff2 = read_ecc[2] ^ calc_ecc[2];
pr_debug("%s: rd %02x%02x%02x calc %02x%02x%02x diff %02x%02x%02x\n",
__func__,
read_ecc[0], read_ecc[1], read_ecc[2],
calc_ecc[0], calc_ecc[1], calc_ecc[2],
diff0, diff1, diff2);
if (diff0 == 0 && diff1 == 0 && diff2 == 0)
return 0; /* ECC is ok */
/* Can we correct this ECC (ie, one row and column change).
* Note, this is similar to the 256 error code on smartmedia */
if (((diff0 ^ (diff0 >> 1)) & 0x55) == 0x55 &&
((diff1 ^ (diff1 >> 1)) & 0x55) == 0x55 &&
((diff2 ^ (diff2 >> 1)) & 0x55) == 0x55) {
/* calculate the bit position of the error */
bit = (diff2 >> 2) & 1;
bit |= (diff2 >> 3) & 2;
bit |= (diff2 >> 4) & 4;
/* calculate the byte position of the error */
byte = (diff1 << 1) & 0x80;
byte |= (diff1 << 2) & 0x40;
byte |= (diff1 << 3) & 0x20;
byte |= (diff1 << 4) & 0x10;
/* we curently have no method for correcting the error */ byte |= (diff0 >> 3) & 0x08;
byte |= (diff0 >> 2) & 0x04;
byte |= (diff0 >> 1) & 0x02;
byte |= (diff0 >> 0) & 0x01;
return -1; byte |= (diff2 << 8) & 0x100;
dev_dbg(info->device, "correcting error bit %d, byte %d\n",
bit, byte);
dat[byte] ^= (1 << bit);
return 1;
}
/* if there is only one bit difference in the ECC, then
* one of only a row or column parity has changed, which
* means the error is most probably in the ECC itself */
diff0 |= (diff1 << 8);
diff0 |= (diff2 << 16);
if ((diff0 & ~(1<<fls(diff0))) == 0)
return 1;
return 0;
} }
/* ECC functions /* ECC functions
...@@ -383,7 +435,8 @@ static int s3c2410_nand_calculate_ecc(struct mtd_info *mtd, const u_char *dat, u ...@@ -383,7 +435,8 @@ static int s3c2410_nand_calculate_ecc(struct mtd_info *mtd, const u_char *dat, u
ecc_code[1] = readb(info->regs + S3C2410_NFECC + 1); ecc_code[1] = readb(info->regs + S3C2410_NFECC + 1);
ecc_code[2] = readb(info->regs + S3C2410_NFECC + 2); ecc_code[2] = readb(info->regs + S3C2410_NFECC + 2);
pr_debug("calculate_ecc: returning ecc %02x,%02x,%02x\n", ecc_code[0], ecc_code[1], ecc_code[2]); pr_debug("%s: returning ecc %02x%02x%02x\n", __func__,
ecc_code[0], ecc_code[1], ecc_code[2]);
return 0; return 0;
} }
...@@ -397,7 +450,7 @@ static int s3c2440_nand_calculate_ecc(struct mtd_info *mtd, const u_char *dat, u ...@@ -397,7 +450,7 @@ static int s3c2440_nand_calculate_ecc(struct mtd_info *mtd, const u_char *dat, u
ecc_code[1] = ecc >> 8; ecc_code[1] = ecc >> 8;
ecc_code[2] = ecc >> 16; ecc_code[2] = ecc >> 16;
pr_debug("calculate_ecc: returning ecc %02x,%02x,%02x\n", ecc_code[0], ecc_code[1], ecc_code[2]); pr_debug("%s: returning ecc %06x\n", __func__, ecc);
return 0; return 0;
} }
......
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