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 | 124 +++++++++++++++---------------------------- 1 file changed, 44 insertions(+), 80 deletions(-)
diff --git a/drivers/mtd/nand/omap_gpmc.c b/drivers/mtd/nand/omap_gpmc.c index fa3a82a..8c2ba53 100644 --- a/drivers/mtd/nand/omap_gpmc.c +++ b/drivers/mtd/nand/omap_gpmc.c @@ -19,6 +19,8 @@
#define SECTOR_BYTES 512 +/* 4 bit padding to make byte aligned, 56 = 52 + 4 */ +#define BCH4_BIT_PAD 4
static uint8_t cs; static __maybe_unused struct nand_ecclayout hw_nand_oob = @@ -319,77 +321,6 @@ static int omap_calculate_ecc_bch(struct mtd_info *mtd, const uint8_t *dat, }
/* - * 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 * @@ -405,16 +336,26 @@ 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; + uint32_t eccbytes = chip->ecc.bytes; uint8_t syndrome[28]; - uint32_t error_count = 0; + uint32_t error_count = 0, error_max; uint32_t error_loc[8]; - uint32_t i, ecc_flag; + uint32_t i, j, ecc_flag = 0; + uint8_t count, ret = 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;
@@ -425,20 +366,43 @@ static int omap_correct_data_bch(struct mtd_info *mtd, uint8_t *dat, * 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); + for (i = 0, j = (eccbytes-1); i < eccbytes; i++, j--) + syndrome[i] = calc_ecc[j];
/* use elm module to check for errors */ if (elm_check_error(syndrome, bch->nibbles, &error_count, error_loc) != 0) { - printf("ECC: uncorrectable.\n"); + printf("nand: uncorrectable ECC errors\n"); return -1; }
/* correct bch error */ - if (error_count > 0) - omap_fix_errors_bch(mtd, dat, error_count, error_loc); + for (count = 0; count < error_count; count++) { + switch (bch->type) { + case ECC_BCH4: + error_max = SECTOR_BYTES + (eccbytes - 1); + /* add 4 to take care 4 bit padding */ + error_loc[count] += BCH4_BIT_PAD; + break; + case ECC_BCH8: + /* 14th byte in ECC is reserved to match ROM layout */ + error_max = SECTOR_BYTES + (eccbytes - 1); + break; + default: + return -1; + } + byte_pos = error_max - ((error_loc[count] - 1) / 8); + bit_pos = error_loc[count] % 8;
- return 0; + if (byte_pos < SECTOR_BYTES) + dat[byte_pos] ^= 1 << bit_pos; + else if (byte_pos < error_max) + read_ecc[byte_pos - SECTOR_BYTES] = 1 << bit_pos; + else + ret = -1; + } + + return ret; }
/**