linux-kernel - Re: [PATCH -next v3 2/2] mtd: nand: toshiba: Add support for Toshiba Memory BENAND (Built-in ECC NAND)

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Date:   Wed, 6 Dec 2017 16:24:04 +0100
From:   Boris Brezillon <boris.brezillon@...e-electrons.com>
To:     KOBAYASHI Yoshitake <yoshitake.kobayashi@...hiba.co.jp>
Cc:     richard@....at, dwmw2@...radead.org, computersforpeace@...il.com,
        marek.vasut@...il.com, cyrille.pitchen@...ev4u.fr,
        linux-mtd@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH -next v3 2/2] mtd: nand: toshiba: Add support for
 Toshiba Memory BENAND (Built-in ECC NAND)

On Wed,  6 Dec 2017 23:04:58 +0900
KOBAYASHI Yoshitake <yoshitake.kobayashi@...hiba.co.jp> wrote:

> This patch enables support for Toshiba Memory BENAND. This checks
> internal ECC status in read operation when using BENAND and selecting
> ECC mode as on-die.
> 
> Signed-off-by: KOBAYASHI Yoshitake <yoshitake.kobayashi@...hiba.co.jp>
> ---
>  drivers/mtd/nand/nand_toshiba.c | 89 +++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 89 insertions(+)
> 
> diff --git a/drivers/mtd/nand/nand_toshiba.c b/drivers/mtd/nand/nand_toshiba.c
> index c2c141b..35c0ddf 100644
> --- a/drivers/mtd/nand/nand_toshiba.c
> +++ b/drivers/mtd/nand/nand_toshiba.c
> @@ -17,6 +17,91 @@
>  
>  #include <linux/mtd/rawnand.h>
>  
> +/* ECC Status Read Command for BENAND */
> +#define TOSHIBA_NAND_CMD_ECC_STATUS	0x7A
> +
> +/* Recommended to rewrite for BENAND */
> +#define TOSHIBA_NAND_STATUS_REWRITE_RECOMMENDED	BIT(3)
> +
> +static int toshiba_nand_benand_status_chk(struct mtd_info *mtd,
> +					  struct nand_chip *chip)
> +{
> +	unsigned int max_bitflips = 0;
> +	u8 status;
> +
> +	/* Check Read Status */
> +	chip->cmdfunc(mtd, NAND_CMD_STATUS, -1, -1);
> +	status = chip->read_byte(mtd);

Please use the recently introduced nand_status_op() helper.

> +
> +	/*
> +	 * TOSHIBA_NAND_CMD_ECC_STATUS is vendor specific command.
> +	 * Currently we have no way to send arbitrary sequences of
> +	 * CMD+ADDR+DATA cycles and thus cannot support this custom
> +	 * TOSHIBA_NAND_CMD_ECC_STATUS operation.

That's about to change :-), if everything goes well, nand_exec_op()
should be available in 4.16.

> +	 * For now, we set max_bitflips mtd->bitflip_threshold.
> +	 */
> +	if (status & NAND_STATUS_FAIL) {
> +		/* uncorrectable */
> +		mtd->ecc_stats.failed++;
> +	} else if (status & TOSHIBA_NAND_STATUS_REWRITE_RECOMMENDED) {
> +		/* correctable */
> +		max_bitflips = mtd->bitflip_threshold;
> +		mtd->ecc_stats.corrected += max_bitflips;
> +	}
> +
> +	return max_bitflips;
> +}
> +
> +static int
> +toshiba_nand_read_page_benand(struct mtd_info *mtd,
> +			      struct nand_chip *chip, uint8_t *buf,
> +			      int oob_required, int page)
> +{
> +	nand_read_page_raw(mtd, chip, buf, oob_required, page);

Please check the return code of nand_read_page_raw().

> +
> +	return toshiba_nand_benand_status_chk(mtd, chip);
> +}
> +
> +static int
> +toshiba_nand_read_subpage_benand(struct mtd_info *mtd,
> +				 struct nand_chip *chip, uint32_t data_offs,
> +				 uint32_t readlen, uint8_t *bufpoi, int page)
> +{
> +	uint8_t *p;
> +
> +	if (data_offs != 0)
> +		chip->cmdfunc(mtd, NAND_CMD_RNDOUT, data_offs, -1);
> +
> +	p = bufpoi + data_offs;
> +	chip->read_buf(mtd, p, readlen);

The core is no longer sending the initial READ0 command, so this should
be turned into:

	ret = nand_read_page_op(chip, data_offs, bufpoi + data_offs,
				readlen);
	if (ret)
		return ret;
		

> +
> +	return toshiba_nand_benand_status_chk(mtd, chip);
> +}
> +
> +static void toshiba_nand_benand_init(struct nand_chip *chip)
> +{
> +	struct mtd_info *mtd = nand_to_mtd(chip);
> +
> +	/*
> +	 * On BENAND, the entire OOB region can be used by the MTD user.
> +	 * The calculated ECC bytes are stored into other isolated
> +	 * area which is not accessible to users.
> +	 * This is why chip->ecc.bytes = 0.
> +	 */
> +	chip->ecc.bytes = 0;
> +	chip->ecc.size = 512;
> +	chip->ecc.strength = 8;
> +	chip->ecc.read_page = toshiba_nand_read_page_benand;
> +	chip->ecc.read_subpage = toshiba_nand_read_subpage_benand;
> +	chip->ecc.write_page = nand_write_page_raw;
> +	chip->ecc.read_page_raw = nand_read_page_raw;
> +	chip->ecc.write_page_raw = nand_write_page_raw;
> +
> +	chip->options |= NAND_SUBPAGE_READ;
> +
> +	mtd_set_ooblayout(mtd, &nand_ooblayout_lp_ops);
> +}
> +
>  static void toshiba_nand_decode_id(struct nand_chip *chip)
>  {
>  	struct mtd_info *mtd = nand_to_mtd(chip);
> @@ -70,6 +155,10 @@ static int toshiba_nand_init(struct nand_chip *chip)
>  	if (nand_is_slc(chip))
>  		chip->bbt_options |= NAND_BBT_SCAN2NDPAGE;
>  
> +	if (nand_is_slc(chip) && (chip->id.data[4] & 0x80) /* BENAND */ &&
> +	    (chip->ecc.mode == NAND_ECC_ON_DIE))
> +		toshiba_nand_benand_init(chip);
> +

Please move this block to toshiba_nand_init().

>  	return 0;
>  }
>