>> >> >> 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.
