Messages in this thread | | | Date | Wed, 20 Jun 2018 12:34:01 +0530 | From | Abhishek Sahu <> | Subject | Re: [PATCH v3 13/16] mtd: rawnand: qcom: minor code reorganization for bad block check |
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On 2018-06-18 17:05, Miquel Raynal wrote: > 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 Miquel.
I will remove this patch from this patch series and will send separate patch series for all bad block handling related changes once things are finalized.
Regards, Abhishek
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