Re: [PATCH v7 1/6] mtd: nand: omap: combine different flavours of 1-bit hamming ecc schemes

[Mark Rutland <mark.rutland@arm.com>]

On Fri, Oct 04, 2013 at 08:49:43PM +0100, Pekon Gupta wrote:
> OMAP NAND driver currently supports multiple flavours of 1-bit Hamming
> ecc-scheme, like:
> - OMAP_ECC_HAMMING_CODE_DEFAULT
> 	1-bit hamming ecc code using software library
> - OMAP_ECC_HAMMING_CODE_HW
> 	1-bit hamming ecc-code using GPMC h/w engine
> - OMAP_ECC_HAMMING_CODE_HW_ROMCODE
> 	1-bit hamming ecc-code using GPMC h/w engin with ecc-layout compatible
> 	to ROM code.
> 
> This patch combines above multiple ecc-schemes into single implementation:
> - OMAP_ECC_HAM1_CODE_HW
> 	1-bit hamming ecc-code using GPMC h/w engine with ROM-code compatible
> 	ecc-layout.

If I have my NAND formatted with one of the existing ECC schemes (e.g.
OMAP_ECC_HAMMING_CODE_DEFAULT) will it work with the new
OMAP_ECC_HAM1_CODE_HW scheme?

Are they all compatible?

> 
> Signed-off-by: Pekon Gupta <pekon@ti.com>
> ---
>  Documentation/devicetree/bindings/mtd/gpmc-nand.txt | 8 ++++----
>  arch/arm/mach-omap2/board-flash.c                   | 2 +-
>  arch/arm/mach-omap2/gpmc.c                          | 4 +---
>  drivers/mtd/nand/omap2.c                            | 9 +++------
>  include/linux/platform_data/mtd-nand-omap2.h        | 6 +-----
>  5 files changed, 10 insertions(+), 19 deletions(-)
> 
> diff --git a/Documentation/devicetree/bindings/mtd/gpmc-nand.txt b/Documentation/devicetree/bindings/mtd/gpmc-nand.txt
> index df338cb..25ee232 100644
> --- a/Documentation/devicetree/bindings/mtd/gpmc-nand.txt
> +++ b/Documentation/devicetree/bindings/mtd/gpmc-nand.txt
> @@ -22,10 +22,10 @@ Optional properties:
>  				width of 8 is assumed.
>  
>   - ti,nand-ecc-opt:		A string setting the ECC layout to use. One of:
> -
> -		"sw"		Software method (default)
> -		"hw"		Hardware method
> -		"hw-romcode"	gpmc hamming mode method & romcode layout
> +		"sw"		<deprecated> use "ham1" instead
> +		"hw"		<deprecated> use "ham1" instead
> +		"hw-romcode"	<deprecated> use "ham1" instead
> +		"ham1"		1-bit Hamming ecc code
>  		"bch4"		4-bit BCH ecc code
>  		"bch8"		8-bit BCH ecc code
>  
> diff --git a/arch/arm/mach-omap2/board-flash.c b/arch/arm/mach-omap2/board-flash.c
> index fc20a61..ac82512 100644
> --- a/arch/arm/mach-omap2/board-flash.c
> +++ b/arch/arm/mach-omap2/board-flash.c
> @@ -142,7 +142,7 @@ __init board_nand_init(struct mtd_partition *nand_parts, u8 nr_parts, u8 cs,
>  	board_nand_data.nr_parts	= nr_parts;
>  	board_nand_data.devsize		= nand_type;
>  
> -	board_nand_data.ecc_opt = OMAP_ECC_HAMMING_CODE_DEFAULT;
> +	board_nand_data.ecc_opt = OMAP_ECC_BCH8_CODE_HW;
>  	gpmc_nand_init(&board_nand_data, gpmc_t);
>  }
>  #endif /* CONFIG_MTD_NAND_OMAP2 || CONFIG_MTD_NAND_OMAP2_MODULE */
> diff --git a/arch/arm/mach-omap2/gpmc.c b/arch/arm/mach-omap2/gpmc.c
> index 9f4795a..1c45b72 100644
> --- a/arch/arm/mach-omap2/gpmc.c
> +++ b/arch/arm/mach-omap2/gpmc.c
> @@ -1342,9 +1342,7 @@ static void __maybe_unused gpmc_read_timings_dt(struct device_node *np,
>  #ifdef CONFIG_MTD_NAND
>  
>  static const char * const nand_ecc_opts[] = {
> -	[OMAP_ECC_HAMMING_CODE_DEFAULT]		= "sw",
> -	[OMAP_ECC_HAMMING_CODE_HW]		= "hw",
> -	[OMAP_ECC_HAMMING_CODE_HW_ROMCODE]	= "hw-romcode",
> +	[OMAP_ECC_HAM1_CODE_HW]			= "ham1",
>  	[OMAP_ECC_BCH4_CODE_HW]			= "bch4",
>  	[OMAP_ECC_BCH8_CODE_HW]			= "bch8",

Won't this break existing dts which have "sw", "hw", or "hw-romcode"?

Someone may try to use a new kernel with an old dt, and we marked them
as deprecated, not removed.

Thanks,
Mark.