linux-kernel - Re: [PATCH 2/2] mtd: nand: gpmi: add support for specific ECC strength

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Message-ID: <20180212113317.7d82f5a0@bbrezillon>
Date:   Mon, 12 Feb 2018 11:33:17 +0100
From:   Boris Brezillon <boris.brezillon@...tlin.com>
To:     Stefan Agner <stefan@...er.ch>
Cc:     han.xu@....com, boris.brezillon@...e-electrons.com,
        marek.vasut@...il.com, richard@....at, dwmw2@...radead.org,
        cyrille.pitchen@...ev4u.fr, max.oss.09@...il.com,
        linux-mtd@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] mtd: nand: gpmi: add support for specific ECC
 strength

On Tue,  6 Feb 2018 18:40:21 +0100
Stefan Agner <stefan@...er.ch> wrote:

> Add support for specified ECC strength/size using device tree
> properties nand-ecc-strength/nand-ecc-step-size.
> 
> Signed-off-by: Stefan Agner <stefan@...er.ch>
> ---
>  .../devicetree/bindings/mtd/gpmi-nand.txt          |  5 ++++
>  drivers/mtd/nand/gpmi-nand/gpmi-nand.c             | 29 ++++++++++++++--------
>  2 files changed, 24 insertions(+), 10 deletions(-)
> 
> diff --git a/Documentation/devicetree/bindings/mtd/gpmi-nand.txt b/Documentation/devicetree/bindings/mtd/gpmi-nand.txt
> index eb2d9919d063..ea6e9b735160 100644
> --- a/Documentation/devicetree/bindings/mtd/gpmi-nand.txt
> +++ b/Documentation/devicetree/bindings/mtd/gpmi-nand.txt
> @@ -46,6 +46,11 @@ Optional properties:
>                         partitions written from Linux with this feature
>                         turned on may not be accessible by the BootROM
>                         code.
> +  - nand-ecc-strength: integer representing the number of bits to correct
> +                       per ECC step. Needs to be a multiple of 2.
> +  - nand-ecc-step-size: integer representing the number of data bytes
> +                       that are covered by a single ECC step. The driver
> +                       supports 512 and 1024.
>  
>  The device tree may optionally contain sub-nodes describing partitions of the
>  address space. See partition.txt for more detail.
> diff --git a/drivers/mtd/nand/gpmi-nand/gpmi-nand.c b/drivers/mtd/nand/gpmi-nand/gpmi-nand.c
> index 50f8d4a1b983..8cb378358e11 100644
> --- a/drivers/mtd/nand/gpmi-nand/gpmi-nand.c
> +++ b/drivers/mtd/nand/gpmi-nand/gpmi-nand.c
> @@ -198,17 +198,15 @@ static inline bool gpmi_check_ecc(struct gpmi_nand_data *this)
>   *
>   * We may have available oob space in this case.
>   */
> -static int set_geometry_by_ecc_info(struct gpmi_nand_data *this)
> +static int set_geometry_by_ecc_info(struct gpmi_nand_data *this,
> +			unsigned int ecc_strength, unsigned int ecc_step)

Nitpick: if you send a new version, could you align the second
parameter on the open parenthesis?

>  {
>  	struct bch_geometry *geo = &this->bch_geometry;
>  	struct nand_chip *chip = &this->nand;
>  	struct mtd_info *mtd = nand_to_mtd(chip);
>  	unsigned int block_mark_bit_offset;
>  
> -	if (!(chip->ecc_strength_ds > 0 && chip->ecc_step_ds > 0))
> -		return -EINVAL;
> -
> -	switch (chip->ecc_step_ds) {
> +	switch (ecc_step) {
>  	case SZ_512:
>  		geo->gf_len = 13;
>  		break;
> @@ -221,8 +219,8 @@ static int set_geometry_by_ecc_info(struct gpmi_nand_data *this)
>  			chip->ecc_strength_ds, chip->ecc_step_ds);
>  		return -EINVAL;
>  	}
> -	geo->ecc_chunk_size = chip->ecc_step_ds;
> -	geo->ecc_strength = round_up(chip->ecc_strength_ds, 2);
> +	geo->ecc_chunk_size = ecc_step;
> +	geo->ecc_strength = round_up(ecc_strength, 2);
>  	if (!gpmi_check_ecc(this))
>  		return -EINVAL;
>  
> @@ -230,7 +228,7 @@ static int set_geometry_by_ecc_info(struct gpmi_nand_data *this)
>  	if (geo->ecc_chunk_size < mtd->oobsize) {
>  		dev_err(this->dev,
>  			"unsupported nand chip. ecc size: %d, oob size : %d\n",
> -			chip->ecc_step_ds, mtd->oobsize);
> +			ecc_step, mtd->oobsize);
>  		return -EINVAL;
>  	}
>  
> @@ -423,9 +421,20 @@ static int legacy_set_geometry(struct gpmi_nand_data *this)
>  
>  int common_nfc_set_geometry(struct gpmi_nand_data *this)
>  {
> +	struct nand_chip *chip = &this->nand;
> +
> +	if (chip->ecc.strength > 0 && chip->ecc.size > 0)
> +		return set_geometry_by_ecc_info(this, chip->ecc.strength,
> +						chip->ecc.size);
> +
>  	if ((of_property_read_bool(this->dev->of_node, "fsl,use-minimum-ecc"))
> -				|| legacy_set_geometry(this))
> -		return set_geometry_by_ecc_info(this);
> +				|| legacy_set_geometry(this)) {
> +		if (!(chip->ecc_strength_ds > 0 && chip->ecc_step_ds > 0))
> +			return -EINVAL;
> +
> +		return set_geometry_by_ecc_info(this, chip->ecc_strength_ds,
> +						chip->ecc_step_ds);
> +	}
>  
>  	return 0;
>  }



-- 
Boris Brezillon, Bootlin (formerly Free Electrons)
Embedded Linux and Kernel engineering
http://bootlin.com