Re: [PATCH v2 04/14] mtd: rawnand: qcom: use the ecc strength from device parameter

[Abhishek Sahu]

On 2018-05-07 13:58, Boris Brezillon wrote:
> On Thu,  3 May 2018 17:50:31 +0530
> Abhishek Sahu <absahu@xxxxxxxxxxxxxx> 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@xxxxxxxxxxxxxx>
> > ---
> > * Changes from v1:
> >
> >   1. Removed the custom logic and used the helper fuction.
> >
> >  drivers/mtd/nand/raw/qcom_nandc.c | 31 
> > ++++++++++++++++++++++---------
> >  1 file changed, 22 insertions(+), 9 deletions(-)
> >
> > diff --git a/drivers/mtd/nand/raw/qcom_nandc.c 
> > b/drivers/mtd/nand/raw/qcom_nandc.c
> > index b554fb6..a8d71ce 100644
> > --- a/drivers/mtd/nand/raw/qcom_nandc.c
> > +++ b/drivers/mtd/nand/raw/qcom_nandc.c
> > @@ -2315,13 +2315,21 @@ 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;
> >
> > @@ -2334,8 +2342,20 @@ static int qcom_nand_host_setup(struct 
> > qcom_nand_host *host)
> >  		return -EINVAL;
> >  	}
> >
> > +	cwperpage = mtd->writesize / ecc->size;
>
> Looks like you're still expecting nand-ecc-step-size to be defined in
> the DT, which does not really make sense since you only support one
> size: NANDC_STEP_SIZE.
>
> You should remove the
>
> 	if (ecc->size != NANDC_STEP_SIZE) {
> 		dev_err(nandc->dev, "invalid ecc size\n");
> 		return -EINVAL;
> 	}
>
> block, then do:
>
> 	cwperpage = mtd->writesize / NANDC_STEP_SIZE;
>
> and finally let the nand_ecc_param_setup() function choose the best
> config for you.

 Correct Boris.
 It only supports one step size so we can remove this DT
 property. I will make the changes.

> > +
> > +	/*
> > +	 * Each CW has 4 available OOB bytes which will be protected with 
> > ECC
> > +	 * so remaining bytes can be used for ECC.
> > +	 */
> > +	ret = nand_ecc_param_setup(chip, &qcom_nandc_ecc_caps,
> > +				   mtd->oobsize - (cwperpage << 2));
>
> Please stop doing useless optimizations like. That brings nothing and
> obfuscates the code a bit more. You say in the comment that each
> codeword has 4 protected OOB bytes that can be used by the upper layer,
> so just do (cwperpage * 4) and let gcc optimize that for you.

 Sure. I will change it.

 Thanks,
 Abhishek

> > +	if (ret) {
> > +		dev_err(nandc->dev, "No valid ecc settings possible\n");
> > +		return ret;
> > +	}
> > +
> >  	wide_bus = chip->options & NAND_BUSWIDTH_16 ? true : false;
> > -
> >  	if (ecc->strength >= 8) {
> >  		/* 8 bit ECC defaults to BCH ECC on all platforms */
> >  		host->bch_enabled = true;
> > @@ -2403,7 +2423,6 @@ 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);
> >
> > @@ -2419,12 +2438,6 @@ 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