With increase in NAND flash densities occurence of bit-flips has increased. Thus stronger ECC schemes are required for detecting and correcting multiple simultaneous bit-flips in same NAND page. But stronger ECC schemes have large ECC syndrome which require more space in OOB/Spare. This patch add support for BCH16_ECC: (a) BCH16_ECC can correct 16 bit-flips per 512Bytes of data. (b) BCH16_ECC generates 26-bytes of ECC syndrome / 512B.
Due to (b) this scheme can only be used with NAND devices which have enough OOB to satisfy following equation: OOBsize per page >= 26 * (page-size / 512) Signed-off-by: Pekon Gupta <[email protected]> --- drivers/mtd/devices/elm.c | 29 +++++++++++++++++++++++++++++ include/linux/platform_data/elm.h | 8 +------- 2 files changed, 30 insertions(+), 7 deletions(-) diff --git a/drivers/mtd/devices/elm.c b/drivers/mtd/devices/elm.c index fca436e..f50f36b 100644 --- a/drivers/mtd/devices/elm.c +++ b/drivers/mtd/devices/elm.c @@ -217,6 +217,35 @@ static void elm_load_syndrome(struct elm_info *info, elm_write_reg(info, (ELM_SYNDROME_FRAGMENT_3 + offset), cpu_to_le32(val)); break; + case BCH16_ECC: + val = *(ecc + 25) << 0 | *(ecc + 24) << 8 | + *(ecc + 23) << 16 | *(ecc + 22) << 24; + elm_write_reg(info, (ELM_SYNDROME_FRAGMENT_0 + + offset), cpu_to_le32(val)); + val = *(ecc + 21) << 0 | *(ecc + 20) << 8 | + *(ecc + 19) << 16 | *(ecc + 18) << 24; + elm_write_reg(info, (ELM_SYNDROME_FRAGMENT_1 + + offset), cpu_to_le32(val)); + val = *(ecc + 17) << 0 | *(ecc + 16) << 8 | + *(ecc + 15) << 16 | *(ecc + 14) << 24; + elm_write_reg(info, (ELM_SYNDROME_FRAGMENT_2 + + offset), cpu_to_le32(val)); + val = *(ecc + 13) << 0 | *(ecc + 12) << 8 | + *(ecc + 11) << 16 | *(ecc + 10) << 24; + elm_write_reg(info, (ELM_SYNDROME_FRAGMENT_3 + + offset), cpu_to_le32(val)); + val = *(ecc + 9) << 0 | *(ecc + 8) << 8 | + *(ecc + 7) << 16 | *(ecc + 6) << 24; + elm_write_reg(info, (ELM_SYNDROME_FRAGMENT_4 + + offset), cpu_to_le32(val)); + val = *(ecc + 5) << 0 | *(ecc + 4) << 8 | + *(ecc + 3) << 16 | *(ecc + 2) << 24; + elm_write_reg(info, (ELM_SYNDROME_FRAGMENT_5 + + offset), cpu_to_le32(val)); + val = *(ecc + 1) << 0 | *(ecc + 0) << 8; + elm_write_reg(info, (ELM_SYNDROME_FRAGMENT_6 + + offset), cpu_to_le32(val)); + break; } } } diff --git a/include/linux/platform_data/elm.h b/include/linux/platform_data/elm.h index d16465b..18b37d8 100644 --- a/include/linux/platform_data/elm.h +++ b/include/linux/platform_data/elm.h @@ -21,19 +21,13 @@ enum bch_ecc { BCH4_ECC = 0, BCH8_ECC, + BCH16_ECC }; /* ELM support 8 error syndrome process */ #define ERROR_VECTOR_MAX 8 #define ELM_MAX_DETECTABLE_ERRORS 16 -#define BCH8_ECC_OOB_BYTES 13 -#define BCH4_ECC_OOB_BYTES 7 -/* RBL requires 14 byte even though BCH8 uses only 13 byte */ -#define BCH8_SIZE (BCH8_ECC_OOB_BYTES + 1) -/* Uses 1 extra byte to handle erased pages */ -#define BCH4_SIZE (BCH4_ECC_OOB_BYTES + 1) - /** * struct elm_errorvec - error vector for elm * @error_reported: set true for vectors error is reported -- 1.8.1 -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
