chip->ecc.correct() is used for detecting and correcting bit-flips during read operations. In omap-nand driver it implemented as: (a) omap_correct_data(): for h/w based ECC_HAM1 scheme (b) omap_correct_data_bch() + CONFIG_NAND_OMAP_ECC_BCH8_CODE_HW_DETECTION_SW for ECC_BCH8 scheme using GPMC and software lib/bch.c (c) omap_correct_data_bch() + CONFIG_NAND_OMAP_ECC_BCH8_CODE_HW for ECC_BCH8 scheme using GPMC and ELM
This patch updates (c) - checks for calc_ecc[]==0x00 so that error_correction is not required for known good pages. - adds scalability for other ECC_BCHx scheme by merging following omap_rotate_ecc_bch() + omap_fix_errors_bch() => omap_correct_data_bch() - fixing logic for bit-flip correction based on error_loc[count]
Signed-off-by: Pekon Gupta pekon@ti.com --- drivers/mtd/nand/omap_gpmc.c | 161 +++++++++++++++++++------------------------ 1 file changed, 71 insertions(+), 90 deletions(-)
diff --git a/drivers/mtd/nand/omap_gpmc.c b/drivers/mtd/nand/omap_gpmc.c index ea1054b..f8616f1 100644 --- a/drivers/mtd/nand/omap_gpmc.c +++ b/drivers/mtd/nand/omap_gpmc.c @@ -21,6 +21,9 @@ #define SECTOR_BYTES 512 #define ECCCLEAR (0x1 << 8) #define ECCRESULTREG1 (0x1 << 0) +/* 4 bit padding to make byte aligned, 56 = 52 + 4 */ +#define BCH4_BIT_PAD 4 + #ifdef CONFIG_BCH static u8 bch8_polynomial[] = {0xef, 0x51, 0x2e, 0x09, 0xed, 0x93, 0x9a, 0xc2, 0x97, 0x79, 0xe5, 0x24, 0xb5}; @@ -179,6 +182,23 @@ static __maybe_unused struct nand_bch_priv bch_priv = { };
/* + * omap_reverse_list - re-orders list elements in reverse order [internal] + * @list: pointer to start of list + * @length: length of list +*/ +void omap_reverse_list(u8 *list, unsigned int length) +{ + unsigned int i, j; + unsigned int half_length = length / 2; + u8 tmp; + for (i = 0, j = length - 1; i < half_length; i++, j--) { + tmp = list[i]; + list[i] = list[j]; + list[j] = tmp; + } +} + +/* * omap_enable_hwecc - configures GPMC as per ECC scheme before read/write * @mtd: MTD device structure * @mode: Read/Write mode @@ -312,77 +332,6 @@ static int omap_calculate_ecc(struct mtd_info *mtd, const uint8_t *dat,
#ifdef CONFIG_NAND_OMAP_ELM /* - * omap_rotate_ecc_bch - Rotate the syndrome bytes - * - * @mtd: MTD device structure - * @calc_ecc: ECC read from ECC registers - * @syndrome: Rotated syndrome will be retuned in this array - * - */ -static void omap_rotate_ecc_bch(struct mtd_info *mtd, uint8_t *calc_ecc, - uint8_t *syndrome) -{ - struct nand_chip *chip = mtd->priv; - struct nand_bch_priv *bch = chip->priv; - uint8_t n_bytes = 0; - int8_t i, j; - - switch (bch->type) { - case ECC_BCH4: - n_bytes = 8; - break; - - case ECC_BCH16: - n_bytes = 28; - break; - - case ECC_BCH8: - default: - n_bytes = 13; - break; - } - - for (i = 0, j = (n_bytes-1); i < n_bytes; i++, j--) - syndrome[i] = calc_ecc[j]; -} - -/* - * omap_fix_errors_bch - Correct bch error in the data - * - * @mtd: MTD device structure - * @data: Data read from flash - * @error_count:Number of errors in data - * @error_loc: Locations of errors in the data - * - */ -static void omap_fix_errors_bch(struct mtd_info *mtd, uint8_t *data, - uint32_t error_count, uint32_t *error_loc) -{ - struct nand_chip *chip = mtd->priv; - struct nand_bch_priv *bch = chip->priv; - uint8_t count = 0; - uint32_t error_byte_pos; - uint32_t error_bit_mask; - uint32_t last_bit = (bch->nibbles * 4) - 1; - - /* Flip all bits as specified by the error location array. */ - /* FOR( each found error location flip the bit ) */ - for (count = 0; count < error_count; count++) { - if (error_loc[count] > last_bit) { - /* Remove the ECC spare bits from correction. */ - error_loc[count] -= (last_bit + 1); - /* Offset bit in data region */ - error_byte_pos = ((512 * 8) - - (error_loc[count]) - 1) / 8; - /* Error Bit mask */ - error_bit_mask = 0x1 << (error_loc[count] % 8); - /* Toggle the error bit to make the correction. */ - data[error_byte_pos] ^= error_bit_mask; - } - } -} - -/* * omap_correct_data_bch - Compares the ecc read from nand spare area * with ECC registers values and corrects one bit error if it has occured * @@ -398,40 +347,72 @@ static int omap_correct_data_bch(struct mtd_info *mtd, uint8_t *dat, { struct nand_chip *chip = mtd->priv; struct nand_bch_priv *bch = chip->priv; - uint8_t syndrome[28]; - uint32_t error_count = 0; + uint32_t eccbytes = chip->ecc.bytes; + uint32_t error_count = 0, error_max; uint32_t error_loc[8]; - uint32_t i, ecc_flag; + uint32_t i, ecc_flag = 0; + uint8_t count, err = 0; + uint32_t byte_pos, bit_pos;
+ /* check calculated ecc */ + for (i = 0; i < chip->ecc.bytes && !ecc_flag; i++) { + if (calc_ecc[i] != 0x00) + ecc_flag = 1; + } + if (!ecc_flag) + return 0; + + /* check for whether its a erased-page */ ecc_flag = 0; - for (i = 0; i < chip->ecc.bytes; i++) + for (i = 0; i < chip->ecc.bytes && !ecc_flag; i++) { if (read_ecc[i] != 0xff) ecc_flag = 1; - + } if (!ecc_flag) return 0;
- elm_reset(); - elm_config((enum bch_level)(bch->type)); - /* * while reading ECC result we read it in big endian. * Hence while loading to ELM we have rotate to get the right endian. */ - omap_rotate_ecc_bch(mtd, calc_ecc, syndrome); - + switch (bch->ecc_scheme) { + case OMAP_ECC_BCH8_CODE_HW: + omap_reverse_list(calc_ecc, eccbytes - 1); + break; + default: + return -EINVAL; + } /* use elm module to check for errors */ - if (elm_check_error(syndrome, bch->nibbles, &error_count, - error_loc) != 0) { - printf("ECC: uncorrectable.\n"); - return -1; + elm_config((enum bch_level)(bch->type)); + if (elm_check_error(calc_ecc, bch->nibbles, &error_count, error_loc)) { + printf("nand: error: uncorrectable ECC errors\n"); + return -EINVAL; } - /* correct bch error */ - if (error_count > 0) - omap_fix_errors_bch(mtd, dat, error_count, error_loc); - - return 0; + for (count = 0; count < error_count; count++) { + switch (bch->type) { + case ECC_BCH8: + /* 14th byte in ECC is reserved to match ROM layout */ + error_max = SECTOR_BYTES + (eccbytes - 1); + break; + default: + return -EINVAL; + } + byte_pos = error_max - (error_loc[count] / 8) - 1; + bit_pos = error_loc[count] % 8; + if (byte_pos < SECTOR_BYTES) { + dat[byte_pos] ^= 1 << bit_pos; + printf("nand: bit-flip corrected @data=%d\n", byte_pos); + } else if (byte_pos < error_max) { + read_ecc[byte_pos - SECTOR_BYTES] = 1 << bit_pos; + printf("nand: bit-flip corrected @oob=%d\n", byte_pos - + SECTOR_BYTES); + } else { + err = -EBADMSG; + printf("nand: error: invalid bit-flip location\n"); + } + } + return (err) ? err : error_count; }
/**