diff options
| -rw-r--r-- | drivers/mtd/nand/nand_base.c | 128 | ||||
| -rw-r--r-- | include/linux/mtd/nand.h | 5 |
2 files changed, 133 insertions, 0 deletions
diff --git a/drivers/mtd/nand/nand_base.c b/drivers/mtd/nand/nand_base.c index 51f7816d67c9..37c0d9d62478 100644 --- a/drivers/mtd/nand/nand_base.c +++ b/drivers/mtd/nand/nand_base.c @@ -1101,6 +1101,134 @@ out: EXPORT_SYMBOL(nand_lock); /** + * nand_check_erased_buf - check if a buffer contains (almost) only 0xff data + * @buf: buffer to test + * @len: buffer length + * @bitflips_threshold: maximum number of bitflips + * + * Check if a buffer contains only 0xff, which means the underlying region + * has been erased and is ready to be programmed. + * The bitflips_threshold specify the maximum number of bitflips before + * considering the region is not erased. + * Note: The logic of this function has been extracted from the memweight + * implementation, except that nand_check_erased_buf function exit before + * testing the whole buffer if the number of bitflips exceed the + * bitflips_threshold value. + * + * Returns a positive number of bitflips less than or equal to + * bitflips_threshold, or -ERROR_CODE for bitflips in excess of the + * threshold. + */ +static int nand_check_erased_buf(void *buf, int len, int bitflips_threshold) +{ + const unsigned char *bitmap = buf; + int bitflips = 0; + int weight; + + for (; len && ((uintptr_t)bitmap) % sizeof(long); + len--, bitmap++) { + weight = hweight8(*bitmap); + bitflips += BITS_PER_BYTE - weight; + if (unlikely(bitflips > bitflips_threshold)) + return -EBADMSG; + } + + for (; len >= sizeof(long); + len -= sizeof(long), bitmap += sizeof(long)) { + weight = hweight_long(*((unsigned long *)bitmap)); + bitflips += BITS_PER_LONG - weight; + if (unlikely(bitflips > bitflips_threshold)) + return -EBADMSG; + } + + for (; len > 0; len--, bitmap++) { + weight = hweight8(*bitmap); + bitflips += BITS_PER_BYTE - weight; + if (unlikely(bitflips > bitflips_threshold)) + return -EBADMSG; + } + + return bitflips; +} + +/** + * nand_check_erased_ecc_chunk - check if an ECC chunk contains (almost) only + * 0xff data + * @data: data buffer to test + * @datalen: data length + * @ecc: ECC buffer + * @ecclen: ECC length + * @extraoob: extra OOB buffer + * @extraooblen: extra OOB length + * @bitflips_threshold: maximum number of bitflips + * + * Check if a data buffer and its associated ECC and OOB data contains only + * 0xff pattern, which means the underlying region has been erased and is + * ready to be programmed. + * The bitflips_threshold specify the maximum number of bitflips before + * considering the region as not erased. + * + * Note: + * 1/ ECC algorithms are working on pre-defined block sizes which are usually + * different from the NAND page size. When fixing bitflips, ECC engines will + * report the number of errors per chunk, and the NAND core infrastructure + * expect you to return the maximum number of bitflips for the whole page. + * This is why you should always use this function on a single chunk and + * not on the whole page. After checking each chunk you should update your + * max_bitflips value accordingly. + * 2/ When checking for bitflips in erased pages you should not only check + * the payload data but also their associated ECC data, because a user might + * have programmed almost all bits to 1 but a few. In this case, we + * shouldn't consider the chunk as erased, and checking ECC bytes prevent + * this case. + * 3/ The extraoob argument is optional, and should be used if some of your OOB + * data are protected by the ECC engine. + * It could also be used if you support subpages and want to attach some + * extra OOB data to an ECC chunk. + * + * Returns a positive number of bitflips less than or equal to + * bitflips_threshold, or -ERROR_CODE for bitflips in excess of the + * threshold. In case of success, the passed buffers are filled with 0xff. + */ +int nand_check_erased_ecc_chunk(void *data, int datalen, + void *ecc, int ecclen, + void *extraoob, int extraooblen, + int bitflips_threshold) +{ + int data_bitflips = 0, ecc_bitflips = 0, extraoob_bitflips = 0; + + data_bitflips = nand_check_erased_buf(data, datalen, + bitflips_threshold); + if (data_bitflips < 0) + return data_bitflips; + + bitflips_threshold -= data_bitflips; + + ecc_bitflips = nand_check_erased_buf(ecc, ecclen, bitflips_threshold); + if (ecc_bitflips < 0) + return ecc_bitflips; + + bitflips_threshold -= ecc_bitflips; + + extraoob_bitflips = nand_check_erased_buf(extraoob, extraooblen, + bitflips_threshold); + if (extraoob_bitflips < 0) + return extraoob_bitflips; + + if (data_bitflips) + memset(data, 0xff, datalen); + + if (ecc_bitflips) + memset(ecc, 0xff, ecclen); + + if (extraoob_bitflips) + memset(extraoob, 0xff, extraooblen); + + return data_bitflips + ecc_bitflips + extraoob_bitflips; +} +EXPORT_SYMBOL(nand_check_erased_ecc_chunk); + +/** * nand_read_page_raw - [INTERN] read raw page data without ecc * @mtd: mtd info structure * @chip: nand chip info structure diff --git a/include/linux/mtd/nand.h b/include/linux/mtd/nand.h index 3140b3d94838..c4d8e308f453 100644 --- a/include/linux/mtd/nand.h +++ b/include/linux/mtd/nand.h @@ -1030,4 +1030,9 @@ struct nand_sdr_timings { /* get timing characteristics from ONFI timing mode. */ const struct nand_sdr_timings *onfi_async_timing_mode_to_sdr_timings(int mode); + +int nand_check_erased_ecc_chunk(void *data, int datalen, + void *ecc, int ecclen, + void *extraoob, int extraooblen, + int threshold); #endif /* __LINUX_MTD_NAND_H */ |