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SubjectRe: [PATCH v2 04/14] mtd: rawnand: qcom: use the ecc strength from device parameter
On Thu,  3 May 2018 17:50:31 +0530
Abhishek Sahu <absahu@codeaurora.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@codeaurora.org>
> ---
> * 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.

> +
> + /*
> + * 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.

> + 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

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