Hi Abhishek, Boris, one question for you below :) > >> >> >> So for last CW, the 464 is BBM (i.e 2048th byte) in > >> >> full page. > >> >> >> > >> >> clear_bam_transaction(nandc); > >> >> >> - ret = copy_last_cw(host, page); > >> >> >> - if (ret) > >> >> >> + clear_read_regs(nandc); > >> >> >> + > >> >> >> + set_address(host, host->cw_size * (ecc->steps - 1), page); > >> >> >> + update_rw_regs(host, 1, true); > >> >> >> + > >> >> >> + /* > >> >> >> + * The last codeword data will be copied from NAND device to NAND > >> >> >> + * controller internal HW buffer. Copy only required BBM size bytes > >> >> >> + * from this HW buffer to bbm_bytes_buf which is present at > >> >> >> + * bbpos offset. > >> >> >> + */ > >> >> >> + nandc_set_read_loc(nandc, 0, bbpos, host->bbm_size, 1); > >> >> >> + config_nand_single_cw_page_read(nandc); > >> >> >> + read_data_dma(nandc, FLASH_BUF_ACC + bbpos, bbm_bytes_buf, > >> >> >> + host->bbm_size, 0); > >> >> >> + > >> >> >> + ret = submit_descs(nandc); > >> >> >> + free_descs(nandc); > >> >> >> + if (ret) { > >> >> >> + dev_err(nandc->dev, "failed to copy bad block bytes\n"); > >> >> >> goto err; > >> >> >> + } > >> >> >> >> flash_status = le32_to_cpu(nandc->reg_read_buf[0]); > >> >> >> >> @@ -2141,12 +2127,10 @@ static int qcom_nandc_block_bad(struct >> mtd_info *mtd, loff_t ofs) > >> >> >> goto err; > >> >> >> } > >> >> >> >> - bbpos = mtd->writesize - host->cw_size * (ecc->steps - 1); > >> >> >> - > >> >> >> - bad = nandc->data_buffer[bbpos] != 0xff; > >> >> >> + bad = bbm_bytes_buf[0] != 0xff; > >> >> > > This is suspect as it still points to the beginning of the data buffer. > >> >> > Can you please check you did not meant bbm_bytes_buf[bbpos]? > >> >> > > >> >> The main thing here is > >> >> nandc_set_read_loc(nandc, 0, bbpos, host->bbm_size, 1); > >> >> >> After reading one complete CW from NAND, the data will be still > >> >> in NAND HW buffer. > >> >> >> The above register tells that we need to read data from > >> >> bbpos of size host->bbm_size (which is 1 byte for 8 bus witdh > >> >> and 2 byte for 16 bus width) in bbm_bytes_buf. > >> > > I see: idx 0 in bbm_bytes_buf is the data at offset bbpos. Then > >> > it's ok. > >> > >> >> So bbm_bytes_buf[0] will contain the BBM first byte. > >> >> and bbm_bytes_buf[1] will contain the BBM second byte. > >> >> >> Regards, > >> >> Abhishek > >> >> >> >> >> if (chip->options & NAND_BUSWIDTH_16) > >> >> >> - bad = bad || (nandc->data_buffer[bbpos + 1] != 0xff); > >> >> >> + bad = bad || (bbm_bytes_buf[1] != 0xff); > >> > > Sorry, my mistake, I did not see the above line. > >> > > However, technically, the BBM could be located in the first, second or > >> > last page of the block. You should check the three of them are 0xFF > >> > before declaring the block is not bad. > >> > > The more I look at the function, the more I wonder if you actually need > >> > it. Why does the generic nand_block_bad() implementation in the core > >> > do not fit? > >> >> The BBM bytes can be accessed in raw mode only for QCOM NAND > >> Contoller. We started with following patch for initial patches > >> >> http://patchwork.ozlabs.org/patch/508565/ > >> >> I am also not very much sure, how can we go ahead now. > >> Ideally we need to use generic function only which > >> requires raw_read. > >> > > I see, thanks for pointing this thread. > > > Well for now then let's keep our driver-specific implementation. > > > I will just ask you to do a consistent check as requested above (you > > can copy code from the core) and add a comment above this function > > explaining why it is needed (what you just told me). > > > Hi Miquel, > > I explored more regarding making custom bad block functions in this > thread and it looks like, we can move to generic block_bad function > by small changes in QCOM NAND driver > only. The main problem was, in read page with ECC, the bad block > byte was skipped. > > But controller is copying the bad block bytes in another register > with following status bytes. > > BAD_BLOCK_STATUS : With every page read operation, when the controller > reads a page with a bad block, it writes the bad block status data into > this register. > > We can update the BBM bytes at start of OOB data in read_oob function > with these status bytes. It will help in getting rid of driver-specific > implementation for chip->block_bad. If think this is acceptable. > > For chip->block_markbad, if we want to get rid of > driver-specific implementation then we can have > following logic > > in write_oob function check for bad block bytes in oob > and do the raw write for updating BBM bytes alone in > flash if BBM bytes are non 0xff. Ok but this will have to be properly explained in a descriptive comment! Maybe Boris can give its point of view on the subject. Is it worth adding the above 'hacks' in the qcom driver and get rid of the driver-specific ->is_bad()/->mark_bad() impementations? 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