tree 28a506167153fa6aa2fb0413411a0d0e7a547e41
parent 136a1cd10633dde22fe64b85f5c92e3b3eba9505
author Abhishek Sahu <absahu@codeaurora.org> 1510040371 +0530
committer Gerrit - the friendly Code Review server <code-review@localhost> 1510054425 -0800

mtd: nand: qcom: reorganize read page error handling

Following are the major issues in current implementation for
checking the read errors

1. For checking the erased CW, NAND_ERASED_CW_DETECT_STATUS
   is being read inside qpic_nand_check_status. The
   qpic_nand_check_status will be called after complete page read
   so reading status register won’t help in getting the register
   value after each CW reads.
2. The mtd layer expects the driver to return non-negative
   integer representing the maximum number of bitflips that were
   corrected on any one ecc region. The mtd layer takes care of
   returning EUCLEAN based on returned number.
3. mtd->ecc_stats is only applicable when ECC engine is
   doing ECC correction. For raw reads, the stats should not be
   incremented.

Now the changes have been done to reorganize the error handling

1. schedule the NAND_ERASED_CW_DETECT_STATUS reading after
   every CW read and check the same if ECC engine generates
   uncorrectable error.
2. For raw read, the ECC engine will never generate the
   uncorrectable error or erased CW so check only
   NAND_FLASH_STATUS.
3. The qpic_nand_read_oob should return the maximum number
   of bitflips that were corrected on any one ecc region so
   introduce the max_bitflips for maintaining the same.
4. The read should return the complete data in case of
   BADMSG so move the BADMSG check in the main read function.

Change-Id: Ibef56294ace00d7cd67b501f623fb1d3aeb2c6ec
Signed-off-by: Abhishek Sahu <absahu@codeaurora.org>