Re: [PATCH v3 2/4] mtd: nand: omap: add support for BCH16_ECC - ELM driver updates

[Brian Norris <computersforpeace@gmail.com>]

On Fri, May 09, 2014 at 02:29:13PM +0530, Pekon Gupta wrote:
> ELM hardware engine is used to detect ECC errors for BCHx ecc-schemes
> (like BCH4/BCH8/BCH16). This patch extends configuration of ELM registers
> for loading of BCH16 ECC syndrome.
> 
> Signed-off-by: Pekon Gupta <pekon@ti.com>
> ---
>  drivers/mtd/devices/elm.c         | 42 +++++++++++++++++++++++++++++++++++++++
>  include/linux/platform_data/elm.h |  3 ++-
>  2 files changed, 44 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/mtd/devices/elm.c b/drivers/mtd/devices/elm.c
> index 1fd4a0f..b4b02a1 100644
> --- a/drivers/mtd/devices/elm.c
> +++ b/drivers/mtd/devices/elm.c
> @@ -213,6 +213,34 @@ static void elm_load_syndrome(struct elm_info *info,
>  				val = cpu_to_be32(*(u32 *) &ecc[0]) >> 12;
>  				elm_write_reg(info, offset, val);
>  				break;
> +			case BCH16_ECC:
> +				val =	ecc[25] << 0  | ecc[24] <<  8 |
> +					ecc[23] << 16 | ecc[22] << 24;

Why can't you use the style of the rest of this switch block? Like:

				val = cpu_to_be32(*(u32 *)&ecc[22]);

Or are there alignment assues with doing this?

Anyway, you need to reconcile these two options, since it looks like
you've only written this for little-endian.

> +				elm_write_reg(info, offset, val);
> +				offset += 4;
> +				val =	ecc[21] <<  0 | ecc[20] <<  8 |
> +					ecc[19] << 16 | ecc[18] << 24;

(Same applies here, and below.)

> +				elm_write_reg(info, offset, val);
> +				offset += 4;
> +				val =	ecc[17] <<  0 | ecc[16] <<  8 |
> +					ecc[15] << 16 | ecc[14] << 24;
> +				elm_write_reg(info, offset, val);
> +				offset += 4;
> +				val =	ecc[13] <<  0 | ecc[12] <<  8 |
> +					ecc[11] << 16 | ecc[10] << 24;
> +				elm_write_reg(info, offset, val);
> +				offset += 4;
> +				val =	ecc[9]  <<  0 | ecc[8]  <<  8 |
> +					ecc[7]  << 16 | ecc[6]  << 24;
> +				elm_write_reg(info, offset, val);
> +				offset += 4;
> +				val =	ecc[5]  <<  0 | ecc[4]  <<  8 |
> +					ecc[3]  << 16 | ecc[2]  << 24;
> +				elm_write_reg(info, offset, val);
> +				offset += 4;
> +				val =	ecc[1]  <<  0 | ecc[0]  <<  8;
> +				elm_write_reg(info, offset, val);
> +				break;
>  			default:
>  				pr_err("invalid config bch_type\n");
>  			}
> @@ -435,6 +463,13 @@ static int elm_context_save(struct elm_info *info)
>  	for (i = 0; i < ERROR_VECTOR_MAX; i++) {
>  		offset = i * SYNDROME_FRAGMENT_REG_SIZE;
>  		switch (bch_type) {
> +		case BCH16_ECC:
> +			regs->elm_syndrome_fragment_6[i] = elm_read_reg(info,
> +					ELM_SYNDROME_FRAGMENT_6 + offset);
> +			regs->elm_syndrome_fragment_5[i] = elm_read_reg(info,
> +					ELM_SYNDROME_FRAGMENT_5 + offset);
> +			regs->elm_syndrome_fragment_4[i] = elm_read_reg(info,
> +					ELM_SYNDROME_FRAGMENT_4 + offset);
>  		case BCH8_ECC:
>  			regs->elm_syndrome_fragment_3[i] = elm_read_reg(info,
>  					ELM_SYNDROME_FRAGMENT_3 + offset);
> @@ -473,6 +508,13 @@ static int elm_context_restore(struct elm_info *info)
>  	for (i = 0; i < ERROR_VECTOR_MAX; i++) {
>  		offset = i * SYNDROME_FRAGMENT_REG_SIZE;
>  		switch (bch_type) {
> +		case BCH16_ECC:
> +			elm_write_reg(info, ELM_SYNDROME_FRAGMENT_6 + offset,
> +					regs->elm_syndrome_fragment_6[i]);
> +			elm_write_reg(info, ELM_SYNDROME_FRAGMENT_5 + offset,
> +					regs->elm_syndrome_fragment_5[i]);
> +			elm_write_reg(info, ELM_SYNDROME_FRAGMENT_4 + offset,
> +					regs->elm_syndrome_fragment_4[i]);
>  		case BCH8_ECC:
>  			elm_write_reg(info, ELM_SYNDROME_FRAGMENT_3 + offset,
>  					regs->elm_syndrome_fragment_3[i]);
> diff --git a/include/linux/platform_data/elm.h b/include/linux/platform_data/elm.h
> index 4edb406..ac2f266 100644
> --- a/include/linux/platform_data/elm.h
> +++ b/include/linux/platform_data/elm.h
> @@ -21,6 +21,7 @@
>  enum bch_ecc {
>  	BCH4_ECC = 0,
>  	BCH8_ECC,
> +	BCH16_ECC
>  };
>  
>  /* ELM support 8 error syndrome process */
> @@ -38,7 +39,7 @@ struct elm_errorvec {
>  	bool error_reported;
>  	bool error_uncorrectable;
>  	int error_count;
> -	int error_loc[ERROR_VECTOR_MAX];
> +	int error_loc[16];
>  };
>  
>  void elm_decode_bch_error_page(struct device *dev, u8 *ecc_calc,

Brian