Add two helper functions to help NAND controller drivers test whether a specific NAND region is erased or not.
Signed-off-by: Boris Brezillon <[email protected]> --- drivers/mtd/nand/nand_base.c | 104 +++++++++++++++++++++++++++++++++++++++++++ include/linux/mtd/nand.h | 8 ++++ 2 files changed, 112 insertions(+) diff --git a/drivers/mtd/nand/nand_base.c b/drivers/mtd/nand/nand_base.c index ceb68ca..1542ea7 100644 --- a/drivers/mtd/nand/nand_base.c +++ b/drivers/mtd/nand/nand_base.c @@ -1101,6 +1101,110 @@ 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 or -ERROR_CODE. + */ +int nand_check_erased_buf(void *buf, int len, int bitflips_threshold) +{ + const unsigned char *bitmap = buf; + int bitflips = 0; + int weight; + int longs; + + for (; len && ((unsigned long)bitmap) % sizeof(long); + len--, bitmap++) { + weight = hweight8(*bitmap); + + bitflips += sizeof(u8) - weight; + if (bitflips > bitflips_threshold) + return -EINVAL; + } + + + for (longs = len / sizeof(long); longs; + longs--, bitmap += sizeof(long)) { + BUG_ON(longs >= INT_MAX / BITS_PER_LONG); + weight = hweight_long(*((unsigned long *)bitmap)); + + bitflips += sizeof(long) - weight; + if (bitflips > bitflips_threshold) + return -EINVAL; + } + + len %= sizeof(long); + + for (; len > 0; len--, bitmap++) { + weight = hweight8(*bitmap); + bitflips += sizeof(u8) - weight; + } + + return bitflips; +} +EXPORT_SYMBOL(nand_check_erased_buf); + +/** + * 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. + * + * Returns a positive number of bitflips or -ERROR_CODE. + */ +int nand_check_erased_ecc_chunk(void *data, int datalen, + void *ecc, int ecclen, + void *extraoob, int extraooblen, + int bitflips_threshold) +{ + int bitflips = 0; + int ret; + + ret = nand_check_erased_buf(data, datalen, bitflips_threshold); + if (ret < 0) + return ret; + + bitflips += ret; + bitflips_threshold -= ret; + + ret = nand_check_erased_buf(ecc, ecclen, bitflips_threshold); + if (ret < 0) + return ret; + + bitflips += ret; + bitflips_threshold -= ret; + + ret = nand_check_erased_buf(extraoob, extraooblen, bitflips_threshold); + if (ret < 0) + return ret; + + return bitflips + ret; +} +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 272f429..ae06a07 100644 --- a/include/linux/mtd/nand.h +++ b/include/linux/mtd/nand.h @@ -1030,4 +1030,12 @@ 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_buf(void *data, int datalen, + int threshold); + +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 */ -- 1.9.1 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
