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 <pekon@xxxxxx>
---
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
--
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