2013/5/16 Gupta, Pekon <pekon@xxxxxx>:
> From: "Gupta, Pekon" <pekon@xxxxxx>
>
> ECC scheme on NAND devices can be implemented in multiple ways.Some using
> Software algorithm, while others using in-build Hardware engines.
> omap2-nand driver currently supports following flavours of ECC schemes,
> selectable via DTB.
>
> +---------------------------------------+---------------+---------------+
> | ECC scheme |ECC calculation|Error detection|
> +---------------------------------------+---------------+---------------+
> |OMAP_ECC_HAMMING_CODE_DEFAULT |S/W |S/W |
> |OMAP_ECC_HAMMING_CODE_HW |H/W (GPMC) |S/W |
> |OMAP_ECC_HAMMING_CODE_HW_ROMCODE |H/W (GPMC) |S/W |
> +---------------------------------------+---------------+---------------+
> |(requires CONFIG_MTD_NAND_ECC_BCH) | | |
> |OMAP_ECC_BCH8_CODE_HW_DETECTION_SW |H/W (GPMC) |S/W |
> +---------------------------------------+---------------+---------------+
> |(requires CONFIG_MTD_NAND_OMAP_BCH) | | |
> |OMAP_ECC_BCH8_CODE_HW |H/W (GPMC) |H/W (ELM) |
> +---------------------------------------+---------------+---------------+
>
> Selection of some ECC schemes also require enabling following Kconfig options.
> This was done to optimize footprint of omap2-nand driver.
> -Kconfig:CONFIG_MTD_NAND_ECC_BCH enables S/W based BCH ECC algorithm
> -Kconfig:CONFIG_MTD_NAND_OMAP_BCH enables H/W based BCH ECC algorithm
>
OMAP_ECC_BCH4_CODE_HW_DETECTION_SW and OMAP_ECC_BCH4_CODE_HW
seems to exist in the code, but are not in the changelog, and not in
the device tree binding documentation.
> Signed-off-by: Gupta, Pekon <pekon@xxxxxx>
> ---
> .../devicetree/bindings/mtd/gpmc-nand.txt | 37 +++++++++++++++-------
> arch/arm/boot/dts/am335x-evm.dts | 2 +-
> arch/arm/mach-omap2/gpmc.c | 12 ++++---
> 3 files changed, 34 insertions(+), 17 deletions(-)
>
> diff --git a/Documentation/devicetree/bindings/mtd/gpmc-nand.txt b/Documentation/devicetree/bindings/mtd/gpmc-nand.txt
> index e7f8d7e..de180be 100644
> --- a/Documentation/devicetree/bindings/mtd/gpmc-nand.txt
> +++ b/Documentation/devicetree/bindings/mtd/gpmc-nand.txt
> @@ -17,20 +17,35 @@ Required properties:
>
> Optional properties:
>
> - - nand-bus-width: Set this numeric value to 16 if the hardware
> - is wired that way. If not specified, a bus
> - width of 8 is assumed.
> + - nand-bus-width: Determines data-width of the connected device
> + x16 = "16"
> + x8 = "8" (default)
>
> - - 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
> - "bch4" 4-bit BCH ecc code
> - "bch8" 8-bit BCH ecc code
> + - ti,nand-ecc-opt: Determines the ECC scheme used by driver.
> + It can be any of the following strings:
> +
> + "hamming_sw" 1-bit Hamming ECC using software
> +
> + "hamming_hw" 1-bit Hamming ECC using hardware
> +
> + "hamming_hw_romcode" 1-bit Hamming ECC using hardware
> + - ECC layout compatible to ROM code
> +
> + "bch8_hw_detection_sw" 8-bit BCH with ECC calculation in hardware
> + and error detection in software
> + - requires Kconfig CONFIG_MTD_NAND_ECC_BCH
> +
> + "bch8_hw" 8-bit BCH with ECC calculation in hardware
> + and error detection in hardware
> + - requires <elm_id> to be specified
> + - requires Kconfig CONFIG_MTD_NAND_OMAP_BCH
> +
> +
> +
> + - elm_id: Specifies elm device node. This is required to
> + support some BCH ECC schemes mentioned above.
>
> - - elm_id: Specifies elm device node. This is required to support BCH
> - error correction using ELM module.
>
> For inline partiton table parsing (optional):
>
> diff --git a/arch/arm/boot/dts/am335x-evm.dts b/arch/arm/boot/dts/am335x-evm.dts
> index 0b8f161..60e8f59 100644
> --- a/arch/arm/boot/dts/am335x-evm.dts
> +++ b/arch/arm/boot/dts/am335x-evm.dts
> @@ -135,7 +135,7 @@
> nand@0,0 {
> reg = <0 0 0>; /* CS0, offset 0 */
> nand-bus-width = <8>;
> - ti,nand-ecc-opt = "bch8";
> + ti,nand-ecc-opt = "bch8_hw";
>
> gpmc,sync-clk = <0>;
> gpmc,cs-on = <0>;
> diff --git a/arch/arm/mach-omap2/gpmc.c b/arch/arm/mach-omap2/gpmc.c
> index 410e1ba..03b8027 100644
> --- a/arch/arm/mach-omap2/gpmc.c
> +++ b/arch/arm/mach-omap2/gpmc.c
> @@ -1205,11 +1205,13 @@ 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_BCH4_CODE_HW] = "bch4",
> - [OMAP_ECC_BCH8_CODE_HW] = "bch8",
> + [OMAP_ECC_HAMMING_CODE_DEFAULT] = "hamming_sw",
> + [OMAP_ECC_HAMMING_CODE_HW] = "hamming_hw",
> + [OMAP_ECC_HAMMING_CODE_HW_ROMCODE] = "hamming_hw_romcode",
> + [OMAP_ECC_BCH4_CODE_HW] = "bch4_hw",
> + [OMAP_ECC_BCH4_CODE_HW_DETECTION_SW] = "bch4_hw_detection_sw",
> + [OMAP_ECC_BCH8_CODE_HW] = "bch8_hw",
> + [OMAP_ECC_BCH8_CODE_HW_DETECTION_SW] = "bch8_hw_detection_sw"
> };
>
> static int gpmc_probe_nand_child(struct platform_device *pdev,
> --
> 1.8.1
>
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