[U-Boot] omap_gpmc: Do not default to HAM1 when SW ECC is selected

[Andreas Bießmann]

Hi Adam,

On 02/18/2015 03:58 AM, Adam YH Lee wrote:
> The ECC scheme selection algorithm in OMAP GPMC appears to be left untested when
> BCH8 handling code was added. Running 'nandecc sw' defaults to HAM1 even if
> the board is using another scheme (ex. OMAP_ECC_BCH8_CODE_HW_DETECTION_SW on
> OMAP3). This results in unrecoverable ECC errors when reading data. This commit
> fixes the behavior by checking for CONFIG_BCH and using the scheme defined by
> CONFIG_NAND_OMAP_ECCSCHEME in the board configuration file.
> 
> This has been tested on Gumstix Overo (OMAP3).
> 
> Signed-off-by: Adam YH Lee <adam.yh.lee at gmail.com>
> ---
>  drivers/mtd/nand/omap_gpmc.c | 5 +++++
>  1 file changed, 5 insertions(+)
> 
> diff --git a/drivers/mtd/nand/omap_gpmc.c b/drivers/mtd/nand/omap_gpmc.c
> index fc64f48..5daf932 100644
> --- a/drivers/mtd/nand/omap_gpmc.c
> +++ b/drivers/mtd/nand/omap_gpmc.c
> @@ -901,8 +901,13 @@ int __maybe_unused omap_nand_switch_ecc(uint32_t hardware, uint32_t eccstrength)
>  			return -EINVAL;
>  		}
>  	} else {
> +		#ifdef CONFIG_BCH
> +		err = omap_select_ecc_scheme(nand, CONFIG_NAND_OMAP_ECCSCHEME,
> +					mtd->writesize, mtd->oobsize);
> +		#else
>  		err = omap_select_ecc_scheme(nand, OMAP_ECC_HAM1_CODE_SW,
>  					mtd->writesize, mtd->oobsize);

Couldn't we just use the CONFIG_NAND_OMAP_ECCSCHEME instead of
OMAP_ECC_HAM1_CODE_SW here and omit the CONFIG_BCH define?

On the other hand I think the whole function omap_nand_switch_ecc() is
wrong. AFAIR it should only be used on omap3 aka am35xx/dm37xx devices
witch the nandecc command.
These SoC do not have a ELM. Therefore I decided to say BCH8 on those
devices is always 'HW ECC' when introduced BCH8 on omap3 first. Nowadays
it is the so called BCH8_CODE_HW_DETECTION_SW. Coming from this mindset
the right solution is to use some detection if the ELM is supported or
not and switch in the HW part of omap_nand_switch_ecc() between
OMAP_ECC_BCH8_CODE_HW and OMAP_ECC_BCH8_CODE_HW_DETECTION_SW.

Best regards

Andreas Bießmann