Detect an erased page, tolerating and correcting up to a specified number of bits at '0'. Downgrade uncorrectable ECC error for an erased page, tolerating 'sectors_per_page' bits at '0'. Signed-off-by: Lee Jones <lee.jones@xxxxxxxxxx> --- drivers/mtd/nand/stm_nand_bch.c | 27 +++++++++++++++++++++++++++ 1 file changed, 27 insertions(+) diff --git a/drivers/mtd/nand/stm_nand_bch.c b/drivers/mtd/nand/stm_nand_bch.c index 2042cdd..7874d85 100644 --- a/drivers/mtd/nand/stm_nand_bch.c +++ b/drivers/mtd/nand/stm_nand_bch.c @@ -319,6 +319,33 @@ static uint8_t bch_erase_block(struct nandi_controller *nandi, } /* + * Detect an erased page, tolerating and correcting up to a specified number of + * bits at '0'. (For many devices, it is now deemed within spec for an erased + * page to include a number of bits at '0', either as a result of read-disturb + * behaviour or 'stuck-at-zero' failures.) Returns the number of corrected + * bits, or a '-1' if we have exceeded the maximum number of bits at '0' (likely + * to be a genuine uncorrectable ECC error). In the latter case, the data must + * be returned unmodified, in accordance with the MTD API. + */ +static int check_erased_page(uint8_t *data, uint32_t page_size, int max_zeros) +{ + uint8_t *b = data; + int zeros = 0; + int i; + + for (i = 0; i < page_size; i++) { + zeros += hweight8(~*b++); + if (zeros > max_zeros) + return -1; + } + + if (zeros) + memset(data, 0xff, page_size); + + return zeros; +} + +/* * Initialisation */ static int bch_check_compatibility(struct nandi_controller *nandi, -- 1.8.3.2 _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@xxxxxxxxxxxxxxxxxxx http://lists.infradead.org/mailman/listinfo/linux-arm-kernel