Re: [PATCH V4 4/9] mtd: get the ECC info from the Extended Parameter Page

[Brian Norris]

Hi Huang,

On Fri, Apr 26, 2013 at 2:08 AM, Huang Shijie <b32955@xxxxxxxxxxxxx> wrote:
> Since the ONFI 2.1, the onfi spec adds the Extended Parameter Page
> to store the ECC info.
>
> The onfi spec tells us that if the nand chip's recommended ECC codeword
> size is not 512 bytes, then the @ecc_bits is 0xff. The host _SHOULD_ then
> read the Extended ECC information that is part of the extended parameter
> page to retrieve the ECC requirements for this device.
>
> This patch implement the reading of the Extended Parameter Page, and parses
> the sections for ECC type, and get the ECC info from the ECC section.
>
> Tested this patch with Micron MT29F64G08CBABAWP.
>
> Signed-off-by: Huang Shijie <b32955@xxxxxxxxxxxxx>
> ---
>  drivers/mtd/nand/nand_base.c |   77 ++++++++++++++++++++++++++++++++++++++++++
>  1 files changed, 77 insertions(+), 0 deletions(-)
>
> diff --git a/drivers/mtd/nand/nand_base.c b/drivers/mtd/nand/nand_base.c
> index beff911..abec615 100644
> --- a/drivers/mtd/nand/nand_base.c
> +++ b/drivers/mtd/nand/nand_base.c
> @@ -2846,6 +2846,68 @@ static u16 onfi_crc16(u16 crc, u8 const *p, size_t len)
>         return crc;
>  }
>
> +/* Parse the Extended Parameter Page. */
> +static int nand_flash_detect_ext_param_page(struct mtd_info *mtd,
> +               struct nand_chip *chip, struct nand_onfi_params *p)
> +{
> +       struct onfi_ext_param_page *ep;
> +       struct onfi_ext_section *s;
> +       struct onfi_ext_ecc_info *ecc;
> +       uint8_t *cursor;
> +       int len;
> +       int ret;
> +       int i;
> +
> +       len = le16_to_cpu(p->ext_param_page_length) * 16;
> +       ep = kmalloc(len, GFP_KERNEL);
> +       if (!ep) {
> +               ret = -ENOMEM;
> +               goto ext_out;
> +       }
> +
> +       /* Send our own NAND_CMD_PARAM. */
> +       chip->cmdfunc(mtd, NAND_CMD_PARAM, 0, -1);
> +
> +       /* Use the Change Read Column command to skip the ONFI param pages. */
> +       chip->cmdfunc(mtd, NAND_CMD_RNDOUT,
> +                       sizeof(*p) * p->num_of_param_pages , -1);
> +
> +       /* Read out the Extended Parameter Page. */
> +       chip->read_buf(mtd, (uint8_t *)ep, len);
> +       if ((onfi_crc16(ONFI_CRC_BASE, ((uint8_t *)ep) + 2, len - 2)
> +               != le16_to_cpu(ep->crc)) || strncmp(ep->sig, "EPPS", 4)) {
> +               pr_debug("fail in the CRC.\n");
> +               ret = -EINVAL;
> +               goto ext_out;
> +       }
> +
> +       /* find the ECC section. */
> +       cursor = (uint8_t *)(ep + 1);
> +       for (i = 0; i < ONFI_EXT_SECTION_MAX; i++) {
> +               s = ep->sections + i;
> +               if (s->type == ONFI_SECTION_TYPE_2)
> +                       break;
> +               cursor += s->length * 16;
> +       }
> +       if (i == ONFI_EXT_SECTION_MAX) {
> +               pr_debug("We can not find the ECC section.\n");
> +               ret = -EINVAL;
> +               goto ext_out;
> +       }
> +
> +       /* get the info we want. */
> +       ecc = (struct onfi_ext_ecc_info *)cursor;
> +       chip->ecc_strength = ecc->ecc_bits;
> +       chip->ecc_size = 1 << ecc->codeword_size;
> +
> +       pr_info("ONFI extended param page detected.\n");
> +       return 0;
> +
> +ext_out:
> +       kfree(ep);
> +       return ret;
> +}
> +
>  /*
>   * Check if the NAND chip is ONFI compliant, returns 1 if it is, 0 otherwise.
>   */
> @@ -2914,6 +2976,21 @@ static int nand_flash_detect_onfi(struct mtd_info *mtd, struct nand_chip *chip,
>         if (p->ecc_bits != 0xff) {
>                 chip->ecc_strength = p->ecc_bits;
>                 chip->ecc_size = 512;
> +       } else if (chip->onfi_version >= 21 &&
> +               (onfi_feature(chip) & ONFI_FEATURE_EXT_PARAM_PAGE)) {
> +
> +               /*
> +                * The nand_flash_detect_ext_param_page() uses the
> +                * Change Read Column command which maybe not supported
> +                * by the chip->cmdfunc. So try to update the chip->cmdfunc
> +                * now. We do not replace user supplied command function.
> +                */
> +               if (mtd->writesize > 512 && chip->cmdfunc == nand_command)
> +                       chip->cmdfunc = nand_command_lp;

I don't think we want to assign chip->cmdfunc within the 'detect_onfi'
function. We already have several places from which the default
functions may be assigned. Rather, we should only code the above
statement *once* (where it already is, in nand_get_flash_type()) and
only run the extended parameter page function after that point.

If that's too cumbersome, then maybe it's fine as-is. Or I'll take a
crack at rewriting it myself.

> +               /* The Extended Parameter Page is supported since ONFI 2.1. */
> +               if (nand_flash_detect_ext_param_page(mtd, chip, p))
> +                       pr_info("Failed to detect the extended param page.\n");
>         }
>
>         pr_info("ONFI flash detected\n");
> --
> 1.7.1
>
>

Brian
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