linux-kernel - Re: [PATCH v3 06/16] mtd: rawnand: qcom: use the ecc strength from device parameter

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Date:   Mon, 28 May 2018 11:31:30 +0530
From:   Abhishek Sahu <absahu@...eaurora.org>
To:     Miquel Raynal <miquel.raynal@...tlin.com>
Cc:     Boris Brezillon <boris.brezillon@...tlin.com>,
        David Woodhouse <dwmw2@...radead.org>,
        Brian Norris <computersforpeace@...il.com>,
        Marek Vasut <marek.vasut@...il.com>,
        Richard Weinberger <richard@....at>,
        Cyrille Pitchen <cyrille.pitchen@...ev4u.fr>,
        linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-mtd@...ts.infradead.org, Andy Gross <andy.gross@...aro.org>,
        Archit Taneja <architt@...eaurora.org>
Subject: Re: [PATCH v3 06/16] mtd: rawnand: qcom: use the ecc strength from
 device parameter

On 2018-05-26 14:13, Miquel Raynal wrote:
> Hi Abhishek,
> 
> On Fri, 25 May 2018 17:51:34 +0530, Abhishek Sahu
> <absahu@...eaurora.org> wrote:
> 
>> Currently the driver uses the ECC strength specified in DT.
>> The QPIC/EBI2 NAND supports 4 or 8-bit ECC correction. The same
>> kind of board can have different NAND parts so use the ECC
>> strength from device parameters if it is not specified in DT.
>> 
>> Signed-off-by: Abhishek Sahu <absahu@...eaurora.org>
>> ---
>> * Changes from v2:
>>   NONE
> 
> Yes you did change things:
> 
> - s/<< 2/* 4/
> - updated the cwperpage location
> - the block handling the ecc-step-size property has been removed in a
>   previous patch
> 
> Please be careful with that, it is time consuming to review the patches
> all over again.
> 

  Sorry Miquel for that.
  I Will pay more attention to this.
  I can understand the effort require in reviewing and how this can help
  in making review quicker.

>> 
>> * Changes from v1:
>> 
>>   1. Removed the custom logic and used the helper fuction.
>> 
>>  drivers/mtd/nand/raw/qcom_nandc.c | 29 +++++++++++++++++++++--------
>>  1 file changed, 21 insertions(+), 8 deletions(-)
>> 
>> diff --git a/drivers/mtd/nand/raw/qcom_nandc.c 
>> b/drivers/mtd/nand/raw/qcom_nandc.c
>> index b538390..7377923 100644
>> --- a/drivers/mtd/nand/raw/qcom_nandc.c
>> +++ b/drivers/mtd/nand/raw/qcom_nandc.c
>> @@ -2315,19 +2315,39 @@ static int qcom_nand_ooblayout_free(struct 
>> mtd_info *mtd, int section,
>>  	.free = qcom_nand_ooblayout_free,
>>  };
>> 
>> +static int
>> +qcom_nandc_calc_ecc_bytes(int step_size, int strength)
>> +{
>> +	return strength == 4 ? 12 : 16;
>> +}
>> +NAND_ECC_CAPS_SINGLE(qcom_nandc_ecc_caps, qcom_nandc_calc_ecc_bytes,
>> +		     NANDC_STEP_SIZE, 4, 8);
>> +
>>  static int qcom_nand_host_setup(struct qcom_nand_host *host)
>>  {
>>  	struct nand_chip *chip = &host->chip;
>>  	struct mtd_info *mtd = nand_to_mtd(chip);
>>  	struct nand_ecc_ctrl *ecc = &chip->ecc;
>>  	struct qcom_nand_controller *nandc = get_qcom_nand_controller(chip);
>> -	int cwperpage, bad_block_byte;
>> +	int cwperpage, bad_block_byte, ret;
>>  	bool wide_bus;
>>  	int ecc_mode = 1;
>> 
>>  	/* controller only supports 512 bytes of data in each step */
>>  	ecc->size = NANDC_STEP_SIZE;
>>  	wide_bus = chip->options & NAND_BUSWIDTH_16 ? true : false;
>> +	cwperpage = mtd->writesize / NANDC_STEP_SIZE;
>> +
>> +	/*
>> +	 * Each CW has 4 available OOB bytes which will be protected with 
>> ECC
>> +	 * so remaining bytes can be used for ECC.
>> +	 */
>> +	ret = nand_ecc_choose_conf(chip, &qcom_nandc_ecc_caps,
>> +				   mtd->oobsize - cwperpage * 4);
> 
> Nitpick: could you add parenthesis around (cwperpage * 4) just for
> clarity.
> 

  Thanks Miquel.
  I will update that.

  Regards,
  Abhishek

>> +	if (ret) {
>> +		dev_err(nandc->dev, "No valid ECC settings possible\n");
>> +		return ret;
>> +	}
>> 
>>  	if (ecc->strength >= 8) {
>>  		/* 8 bit ECC defaults to BCH ECC on all platforms */
>> @@ -2396,7 +2416,6 @@ static int qcom_nand_host_setup(struct 
>> qcom_nand_host *host)
>> 
>>  	mtd_set_ooblayout(mtd, &qcom_nand_ooblayout_ops);
>> 
>> -	cwperpage = mtd->writesize / ecc->size;
>>  	nandc->max_cwperpage = max_t(unsigned int, nandc->max_cwperpage,
>>  				     cwperpage);
>> 
>> @@ -2412,12 +2431,6 @@ static int qcom_nand_host_setup(struct 
>> qcom_nand_host *host)
>>  	 * for 8 bit ECC
>>  	 */
>>  	host->cw_size = host->cw_data + ecc->bytes;
>> -
>> -	if (ecc->bytes * (mtd->writesize / ecc->size) > mtd->oobsize) {
>> -		dev_err(nandc->dev, "ecc data doesn't fit in OOB area\n");
>> -		return -EINVAL;
>> -	}
>> -
>>  	bad_block_byte = mtd->writesize - host->cw_size * (cwperpage - 1) + 
>> 1;
>> 
>>  	host->cfg0 = (cwperpage - 1) << CW_PER_PAGE
> 
> Once corrected:
> 
> Acked-by: Miquel Raynal <miquel.raynal@...tlin.com>
> 
> Thanks,
> Miquèl