[U-Boot] [PATCH v7 1/5] mtd: nand: omap: enable BCH ECC scheme using ELM for generic platform

[Scott Wood]

On Mon, 2013-09-30 at 19:43 +0530, Pekon Gupta wrote:
> +Platform specific options
> +=========================
> +
> +   CONFIG_NAND_OMAP_ECCSCHEME
> +	On OMAP platforms, this specifies NAND ECC scheme.
> +	1 - HAM1_SW	1-bit Hamming code using software library
> +			(for legacy devices only)
> +	2 - HAM1_HW	1-bit Hamming code using GPMC hardware engine
> +			(for legacy devices only)
> +	3 - BCH4_SW	4-bit BCH code (unsupported)
> +	4 - BCH4_HW	4-bit BCH code (unsupported)
> +	5 - BCH8_SW	8-bit BCH code with
> +			- ecc calculation using GPMC hardware engine,
> +			- error detection using software library.
> +			- requires CONFIG_BCH to enable software BCH library
> +			(For legacy device which do not have ELM h/w engine)
> +	6 - BCH8_HW	8-bit BCH code with
> +			- ecc calculation using GPMC hardware engine,
> +			- error detection using ELM hardware engine.

You should document the symbols, not the numbers that happen to be
assigned to them.

> +/**
> + * omap_select_ecc_scheme - configures driver for particular ecc-scheme
> + * @nand: NAND chip device structure
> + * @ecc_scheme: ecc scheme to configure
> + * @pagesize: number of main-area bytes per page of NAND device
> + * @oobsize: number of OOB/spare bytes per page of NAND device
> + */
> +static int omap_select_ecc_scheme(struct nand_chip *nand, int ecc_scheme,
> +		unsigned int pagesize, unsigned int oobsize) {

s/int ecc_scheme/enum omap_ecc ecc_scheme/

> +	struct nand_bch_priv	*bch		= nand->priv;
> +	struct nand_ecclayout	*ecclayout	= nand->ecc.layout;
> +	int i;
> +
> +	switch (ecc_scheme) {
> +	case OMAP_ECC_HAM1_CODE_SW:
> +		debug("nand: selected OMAP_ECC_HAM1_CODE_SW\n");
> +		nand->ecc.mode		= NAND_ECC_SOFT;
> +		nand->ecc.layout	= NULL;
> +		nand->ecc.size		= 0;
> +		nand->ecc.strength	= 1;
> +		bch->ecc_scheme		= OMAP_ECC_HAM1_CODE_SW;
> +		break;
> +	case OMAP_ECC_HAM1_CODE_HW:
> +		debug("nand: selected OMAP_ECC_HAM1_CODE_HW\n");
> +		nand->ecc.mode		= NAND_ECC_HW;
> +		nand->ecc.strength	= 1;
> +		nand->ecc.size		= 512;
> +		nand->ecc.bytes		= 3;
> +		nand->ecc.hwctl		= omap_enable_hwecc;
> +		nand->ecc.correct	= omap_correct_data;
> +		nand->ecc.calculate	= omap_calculate_ecc;
> +		/* define ecc-layout */
> +		ecclayout->eccbytes	= nand->ecc.bytes *
> +						(pagesize / SECTOR_BYTES);
> +		for (i = 0; i < ecclayout->eccbytes; i++)
> +			ecclayout->eccpos[i] = i + BADBLOCK_MARKER_LENGTH;
> +		ecclayout->oobfree[0].offset = i + BADBLOCK_MARKER_LENGTH;
> +		ecclayout->oobfree[0].length = oobsize - ecclayout->eccbytes -
> +						BADBLOCK_MARKER_LENGTH;
> +		bch->ecc_scheme		= OMAP_ECC_HAM1_CODE_HW;
> +		break;
> +#ifdef CONFIG_BCH
> +	case OMAP_ECC_BCH8_CODE_HW_DETECTION_SW:
> +		debug("nand: selected OMAP_ECC_BCH8_CODE_HW_DETECTION_SW\n");
> +		nand->ecc.mode		= NAND_ECC_HW;
> +		nand->ecc.strength	= 8;
> +		nand->ecc.size		= 512;
> +		nand->ecc.bytes		= 13;
> +		nand->ecc.hwctl		= omap_enable_ecc_bch;
> +		nand->ecc.correct	= omap_correct_data_bch_sw;
> +		nand->ecc.calculate	= omap_calculate_ecc_bch_sw;
> +		/* BCH SW library is used for error detection */
> +		bch_priv.control	= init_bch(13, 8, 0x201b);
> +		if (!bch_priv.control) {
> +			printf("nand: error: could not init_bch()\n");
> +			return -ENODEV;
> +		}
> +		bch_priv.type		= ECC_BCH8;
> +		/* define ecc-layout */
> +		ecclayout->eccbytes	= nand->ecc.bytes *
> +						(pagesize / SECTOR_BYTES);
> +		for (i = 0; i < ecclayout->eccbytes; i++)
> +			ecclayout->eccpos[i] = i + (oobsize -
> +						ecclayout->eccbytes);
> +		ecclayout->oobfree[0].offset = BADBLOCK_MARKER_LENGTH;
> +		ecclayout->oobfree[0].length = oobsize - ecclayout->eccbytes -
> +						BADBLOCK_MARKER_LENGTH;
> +		omap_hwecc_init_bch(nand, NAND_ECC_READ);
> +		bch->ecc_scheme		= OMAP_ECC_BCH8_CODE_HW_DETECTION_SW;
> +		break;
> +#endif
> +	case OMAP_ECC_BCH8_CODE_HW:
> +		debug("nand: selected OMAP_ECC_BCH8_CODE_HW\n");
> +		nand->ecc.mode		= NAND_ECC_HW;
> +		nand->ecc.strength	= 8;
> +		nand->ecc.size		= 512;
> +		nand->ecc.bytes		= 14;
> +		nand->ecc.hwctl		= omap_enable_ecc_bch;
> +		nand->ecc.correct	= omap_correct_data_bch;
> +		nand->ecc.calculate	= omap_calculate_ecc_bch;
> +		nand->ecc.read_page	= omap_read_page_bch;
> +		/* ELM is used for ECC error detection */
> +		elm_init();
> +		bch_priv.type		= ECC_BCH8;
> +		/* define ecc-layout */
> +		ecclayout->eccbytes	= nand->ecc.bytes *
> +						(pagesize / SECTOR_BYTES);
> +		for (i = 0; i < ecclayout->eccbytes; i++)
> +			ecclayout->eccpos[i] = i + BADBLOCK_MARKER_LENGTH;
> +		ecclayout->oobfree[0].offset = i + BADBLOCK_MARKER_LENGTH;
> +		ecclayout->oobfree[0].length = oobsize - ecclayout->eccbytes -
> +						BADBLOCK_MARKER_LENGTH;
> +		bch->ecc_scheme		= OMAP_ECC_BCH8_CODE_HW;
> +		break;
> +	default:
> +		debug("nand: error: ecc scheme not enabled or supported\n");
> +		return -EINVAL;
> +	}
> +
> +	/* check if NAND spare/OOB has enough bytes to accomodate ecclayout */
> +	if ((ecclayout->eccbytes + BADBLOCK_MARKER_LENGTH) > oobsize) {
> +		printf("nand: error: insufficient OOB bytes. require=%d\n", (
> +				ecclayout->eccbytes + BADBLOCK_MARKER_LENGTH));
> +		return -EINVAL;
> +	}

Check this before you make any changes to the current ECC setup.

> +		err = omap_select_ecc_scheme(nand, OMAP_ECC_HAM1_CODE_SW,
> +					mtd->writesize, mtd->oobsize);
> +	}
> +	if (err) {
> +		printf("nand: error: could not switch ecc, reverting\n");
> +		omap_select_ecc_scheme(nand, bch->ecc_scheme,
> +				       mtd->writesize, mtd->oobsize);
> +		return -EINVAL;
>  	}

You won't need to "revert" here if omap_select_ecc_scheme doesn't damage
anything in error cases.

-Scott