[U-Boot] [PATCH v4 4/5] mtd: nand: omap: optimized chip->ecc.correct() for H/W ECC schemes
Pekon Gupta
pekon at ti.com
Tue Sep 3 07:56:31 CEST 2013
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 at ti.com>
---
drivers/mtd/nand/omap_gpmc.c | 127 +++++++++++++++----------------------------
1 file changed, 45 insertions(+), 82 deletions(-)
diff --git a/drivers/mtd/nand/omap_gpmc.c b/drivers/mtd/nand/omap_gpmc.c
index a926cdd..08d59cc 100644
--- a/drivers/mtd/nand/omap_gpmc.c
+++ b/drivers/mtd/nand/omap_gpmc.c
@@ -21,6 +21,8 @@
#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
static uint8_t cs;
static __maybe_unused struct nand_ecclayout omap_ecclayout;
@@ -317,77 +319,6 @@ static int omap_calculate_ecc(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
*
@@ -403,16 +334,26 @@ 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, 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;
@@ -423,20 +364,42 @@ 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");
- return -1;
+ 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_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 -EINVAL;
+ }
+ byte_pos = error_max - ((error_loc[count] - 1) / 8);
+ bit_pos = error_loc[count] % 8;
+
+ 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
+ err = -EBADMSG;
+ }
+ return (err) ? err : error_count;
}
/*
--
1.8.1
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