Hi Abhishek, Abhishek Sahu <absahu@xxxxxxxxxxxxxx> wrote on Tue, 3 Jul 2018 17:36:03 +0530: > NAND parts can have bitflips in an erased page due to the > process technology used. In this case, QCOM NAND controller > is not able to identify that page as an erased page. > Currently the driver calls nand_check_erased_ecc_chunk() for > identifying the erased pages but this won’t work always since the > checking is being with ECC engine returned data. In case of > bitflips, the ECC engine tries to correct the data and then it > generates the uncorrectable error. Now, this data is not equal to > original raw data. For erased CW identification, the raw data > should be read again from NAND device and this > nand_check_erased_ecc_chunk function() should be called for raw > data only. > > Now following logic is being added to identify the erased > codeword bitflips. > > 1. In most of the cases, not all the codewords will have bitflips > and only single CW will have bitflips. So, there is no need to > read the complete raw page data. The NAND raw read can be > scheduled for any CW in page. The NAND controller works on CW > basis and it will update the status register after each CW read. > Maintain the bitmask for the CW which generated the uncorrectable > error. > 2. Do raw read for all the CW's which generated the uncorrectable > error. > 3. Both DATA and OOB need to be checked for number of 0. The > top-level API can be called with only data buf or OOB buf so use > chip->databuf if data buf is null and chip->oob_poi if > OOB buf is null for copying the raw bytes temporarily. > 4. For each CW, check the number of 0 in cw_data and usable > oob bytes, The bbm and spare (unused) bytes bit flip won’t > affect the ECC so don’t check the number of bitflips in this area. > > Signed-off-by: Abhishek Sahu <absahu@xxxxxxxxxxxxxx> > --- > * Changes from v4: > > 1. Used for_each_set_bit for determining CW’s which generated > uncorrectable errors. > 2. Introduced cw_data_buf and cw_oob_buf which will have starting > buffer address for current codeword and used the same in helper > functions. > 3. Added new line before calling of nand_check_erased_ecc_chunk for > better code readability. > > * Changes from v3: > > 1. Major changes in erased codeword detection for > raw read function > > * Changes from v2: > NONE > > * Changes from v1: > 1. Minor change in commit message > 2. invalidate pagebuf if databuf or oob_poi is used > > drivers/mtd/nand/raw/qcom_nandc.c | 126 +++++++++++++++++++++++++++----------- > 1 file changed, 89 insertions(+), 37 deletions(-) Applied to nand/next. Thanks, Miquèl -- To unsubscribe from this list: send the line "unsubscribe linux-arm-msm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
