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

[Han Xu]

On 02/06/2018 11:40 AM, Stefan Agner 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@xxxxxxxx>
> ---
>   .../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)
>   {
>   	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);
> +

I was wondering how to keep, let's say u-boot, and kernel ecc setting 
aligned, if users can specify the strength and step_ds in DT? Did u-boot 
enable to get these parameters from DT?
>   	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;
>   }