Re: [PATCH v8 4/6] mtd:nand:omap2: updated support for BCH4 ECC scheme

[Felipe Balbi <balbi@ti.com>]

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On Fri, Oct 11, 2013 at 07:06:41PM +0530, Pekon Gupta wrote:
> This patch adds following two flavours of BCH4 ECC scheme in omap2-nand driver
> - OMAP_ECC_BCH4_CODE_HW_DETECTION_SW
> 	- uses GPMC H/W engine for calculating ECC.
> 	- uses software library (lib/bch.h & nand_bch.h) for error correction.
> 
> - OMAP_ECC_BCH4_CODE_HW
> 	- uses GPMC H/W engine for calculating ECC.
> 	- uses ELM H/W engine for error correction.
> 
> With this patch omap2-nand driver supports following ECC schemes:
> +---------------------------------------+---------------+---------------+
> | ECC scheme                            |ECC calculation|Error detection|
> +---------------------------------------+---------------+---------------+
> |OMAP_ECC_HAM1_CODE_HW                  |H/W (GPMC)     |S/W            |
> +---------------------------------------+---------------+---------------+
> |OMAP_ECC_BCH4_CODE_HW_DETECTION_SW     |H/W (GPMC)     |S/W (lib/bch.h)|
> |OMAP_ECC_BCH4_CODE_HW                  |H/W (GPMC)     |H/W (ELM)      |
> +---------------------------------------+---------------+---------------+
> |OMAP_ECC_BCH8_CODE_HW_DETECTION_SW     |H/W (GPMC)     |S/W (lib/bch.h)|
> |OMAP_ECC_BCH8_CODE_HW                  |H/W (GPMC)     |H/W (ELM)      |
> +---------------------------------------+---------------+---------------+
> Important:
> - Selection of OMAP_ECC_BCHx_CODE_HW_DETECTION_SW requires,
> 	Kconfig: CONFIG_MTD_NAND_ECC_BCH: enables S/W based BCH ECC algorithm.
> 
> - Selection of OMAP_ECC_BCHx_CODE_HW requires,
> 	Kconfig: CONFIG_MTD_NAND_OMAP_BCH: enables ELM H/W module.
> 
> Signed-off-by: Pekon Gupta <pekon@ti.com>

Reviewed-by: Felipe Balbi <balbi@ti.com>

> ---
>  drivers/mtd/nand/Kconfig |  30 ++---------
>  drivers/mtd/nand/omap2.c | 134 +++++++++++++++++++++--------------------------
>  2 files changed, 63 insertions(+), 101 deletions(-)
> 
> diff --git a/drivers/mtd/nand/Kconfig b/drivers/mtd/nand/Kconfig
> index d885298..5836039 100644
> --- a/drivers/mtd/nand/Kconfig
> +++ b/drivers/mtd/nand/Kconfig
> @@ -96,35 +96,13 @@ config MTD_NAND_OMAP2
>  
>  config MTD_NAND_OMAP_BCH
>  	depends on MTD_NAND && MTD_NAND_OMAP2 && ARCH_OMAP3
> -	tristate "Enable support for hardware BCH error correction"
> +	tristate "Support hardware based BCH error correction"
>  	default n
>  	select BCH
> -	select BCH_CONST_PARAMS
>  	help
> -	 Support for hardware BCH error correction.
> -
> -choice
> -	prompt "BCH error correction capability"
> -	depends on MTD_NAND_OMAP_BCH
> -
> -config MTD_NAND_OMAP_BCH8
> -	bool "8 bits / 512 bytes (recommended)"
> -	help
> -	 Support correcting up to 8 bitflips per 512-byte block.
> -	 This will use 13 bytes of spare area per 512 bytes of page data.
> -	 This is the recommended mode, as 4-bit mode does not work
> -	 on some OMAP3 revisions, due to a hardware bug.
> -
> -config MTD_NAND_OMAP_BCH4
> -	bool "4 bits / 512 bytes"
> -	help
> -	 Support correcting up to 4 bitflips per 512-byte block.
> -	 This will use 7 bytes of spare area per 512 bytes of page data.
> -	 Note that this mode does not work on some OMAP3 revisions, due to a
> -	 hardware bug. Please check your OMAP datasheet before selecting this
> -	 mode.
> -
> -endchoice
> +	  Some devices have built-in ELM hardware engine, which can be used to
> +	  locate and correct errors when using BCH ECC scheme. This enables the
> +	  driver support for same.
>  
>  if MTD_NAND_OMAP_BCH
>  config BCH_CONST_M
> diff --git a/drivers/mtd/nand/omap2.c b/drivers/mtd/nand/omap2.c
> index fb96251..a783dae 100644
> --- a/drivers/mtd/nand/omap2.c
> +++ b/drivers/mtd/nand/omap2.c
> @@ -27,6 +27,7 @@
>  
>  #ifdef CONFIG_MTD_NAND_ECC_BCH
>  #include <linux/bch.h>
> +#include <linux/mtd/nand_bch.h>
>  #endif
>  #ifdef CONFIG_MTD_NAND_OMAP_BCH
>  #include <linux/platform_data/elm.h>
> @@ -144,7 +145,6 @@
>  #define BCH_ECC_SIZE1		0x20	/* ecc_size1 = 32 */
>  
>  #define BADBLOCK_MARKER_LENGTH		2
> -#define OMAP_ECC_BCH8_POLYNOMIAL	0x201b
>  
>  #ifdef CONFIG_MTD_NAND_OMAP_BCH
>  static u_char bch8_vector[] = {0xf3, 0xdb, 0x14, 0x16, 0x8b, 0xd2, 0xbe, 0xcc,
> @@ -188,7 +188,6 @@ struct omap_nand_info {
>  	int					buf_len;
>  	struct gpmc_nand_regs		reg;
>  	/* fields specific for BCHx_HW ECC scheme */
> -	struct bch_control              *bch;
>  	bool				is_elm_used;
>  	struct device			*elm_dev;
>  	struct device_node		*of_node;
> @@ -1522,43 +1521,7 @@ static int omap_elm_correct_data(struct mtd_info *mtd, u_char *data,
>  
>  	return stat;
>  }
> -#endif /* CONFIG_MTD_NAND_OMAP_BCH */
>  
> -#ifdef CONFIG_MTD_NAND_ECC_BCH
> -/**
> - * omap3_correct_data_bch - Decode received data and correct errors
> - * @mtd: MTD device structure
> - * @data: page data
> - * @read_ecc: ecc read from nand flash
> - * @calc_ecc: ecc read from HW ECC registers
> - */
> -static int omap3_correct_data_bch(struct mtd_info *mtd, u_char *data,
> -				  u_char *read_ecc, u_char *calc_ecc)
> -{
> -	int i, count;
> -	/* cannot correct more than 8 errors */
> -	unsigned int errloc[8];
> -	struct omap_nand_info *info = container_of(mtd, struct omap_nand_info,
> -						   mtd);
> -
> -	count = decode_bch(info->bch, NULL, 512, read_ecc, calc_ecc, NULL,
> -			   errloc);
> -	if (count > 0) {
> -		/* correct errors */
> -		for (i = 0; i < count; i++) {
> -			/* correct data only, not ecc bytes */
> -			if (errloc[i] < 8*512)
> -				data[errloc[i]/8] ^= 1 << (errloc[i] & 7);
> -			pr_debug("corrected bitflip %u\n", errloc[i]);
> -		}
> -	} else if (count < 0) {
> -		pr_err("ecc unrecoverable error\n");
> -	}
> -	return count;
> -}
> -#endif /* CONFIG_MTD_NAND_ECC_BCH */
> -
> -#ifdef CONFIG_MTD_NAND_OMAP_BCH
>  /**
>   * omap_write_page_bch - BCH ecc based write page function for entire page
>   * @mtd:		mtd info structure
> @@ -1675,28 +1638,6 @@ static int is_elm_present(struct omap_nand_info *info,
>  }
>  #endif /* CONFIG_MTD_NAND_ECC_BCH */
>  
> -#ifdef CONFIG_MTD_NAND_ECC_BCH
> -/**
> - * omap3_free_bch - Release BCH ecc resources
> - * @mtd: MTD device structure
> - */
> -static void omap3_free_bch(struct mtd_info *mtd)
> -{
> -	struct omap_nand_info *info = container_of(mtd, struct omap_nand_info,
> -						   mtd);
> -	if (info->bch) {
> -		free_bch(info->bch);
> -		info->bch = NULL;
> -	}
> -}
> -
> -#else
> -
> -static void omap3_free_bch(struct mtd_info *mtd)
> -{
> -}
> -#endif /* CONFIG_MTD_NAND_ECC_BCH */
> -
>  static int omap_nand_probe(struct platform_device *pdev)
>  {
>  	struct omap_nand_info		*info;
> @@ -1731,10 +1672,10 @@ static int omap_nand_probe(struct platform_device *pdev)
>  	mtd->owner		= THIS_MODULE;
>  	mtd->priv		= &info->nand;
>  	nand_chip		= &info->nand;
> +	nand_chip->ecc.priv	= NULL;
>  	info->pdev		= pdev;
>  	info->gpmc_cs		= pdata->cs;
>  	info->reg		= pdata->reg;
> -	info->bch		= NULL;
>  
>  	nand_chip->options	|= NAND_SKIP_BBTSCAN | NAND_BUSWIDTH_AUTO;
>  	info->of_node		= pdata->of_node;
> @@ -1927,7 +1868,7 @@ static int omap_nand_probe(struct platform_device *pdev)
>  		nand_chip->ecc.bytes		= 7;
>  		nand_chip->ecc.strength		= 4;
>  		nand_chip->ecc.hwctl		= omap3_enable_hwecc_bch;
> -		nand_chip->ecc.correct		= omap3_correct_data_bch;
> +		info->nand.ecc.correct		= nand_bch_correct_data;
>  		nand_chip->ecc.calculate	= omap3_calculate_ecc_bch4;
>  		/* define custom ECC layout */
>  		ecclayout->eccbytes		= nand_chip->ecc.bytes *
> @@ -1937,10 +1878,11 @@ static int omap_nand_probe(struct platform_device *pdev)
>  		ecclayout->oobfree->offset	= ecclayout->eccpos[0] +
>  							ecclayout->eccbytes;
>  		/* software bch library is used for locating errors */
> -		info->bch = init_bch(nand_chip->ecc.bytes,
> -					nand_chip->ecc.strength,
> -					OMAP_ECC_BCH8_POLYNOMIAL);
> -		if (!info->bch) {
> +		info->nand.ecc.priv		= nand_bch_init(mtd,
> +							info->nand.ecc.size,
> +							info->nand.ecc.bytes,
> +							&info->nand.ecc.layout);
> +		if (!info->nand.ecc.priv) {
>  			pr_err("nand: error: unable to use s/w BCH library\n");
>  			err = -EINVAL;
>  		}
> @@ -1951,6 +1893,39 @@ static int omap_nand_probe(struct platform_device *pdev)
>  		goto out_release_mem_region;
>  #endif
>  
> +	case OMAP_ECC_BCH4_CODE_HW:
> +#ifdef CONFIG_MTD_NAND_OMAP_BCH
> +		pr_info("nand: using OMAP_ECC_BCH4_CODE_HW ECC scheme\n");
> +		info->nand.ecc.mode		= NAND_ECC_HW;
> +		info->nand.ecc.size		= 512;
> +		/* 14th bit is kept reserved for ROM-code compatibility */
> +		info->nand.ecc.bytes		= 7 + 1;
> +		info->nand.ecc.strength		= 4;
> +		info->nand.ecc.hwctl		= omap3_enable_hwecc_bch;
> +		info->nand.ecc.correct		= omap_elm_correct_data;
> +		info->nand.ecc.calculate	= omap3_calculate_ecc_bch;
> +		info->nand.ecc.read_page	= omap_read_page_bch;
> +		info->nand.ecc.write_page	= omap_write_page_bch;
> +		/* This ECC scheme requires ELM H/W block */
> +		if (is_elm_present(info, pdata->elm_of_node, BCH4_ECC) < 0) {
> +			pr_err("nand: error: could not initialize ELM\n");
> +			err = -ENODEV;
> +			goto out_release_mem_region;
> +		}
> +		/* define ECC layout */
> +		ecclayout->eccbytes		= info->nand.ecc.bytes *
> +							(mtd->writesize /
> +							info->nand.ecc.size);
> +		ecclayout->eccpos[0]		= BADBLOCK_MARKER_LENGTH;
> +		ecclayout->oobfree->offset	= ecclayout->eccpos[0] +
> +							ecclayout->eccbytes;
> +		break;
> +#else
> +		pr_err("nand: error: CONFIG_MTD_NAND_OMAP_BCH not enabled\n");
> +		err = -EINVAL;
> +		goto out_release_mem_region;
> +#endif
> +
>  	case OMAP_ECC_BCH8_CODE_HW_DETECTION_SW:
>  #ifdef CONFIG_MTD_NAND_ECC_BCH
>  		pr_info("nand: using OMAP_ECC_BCH8_CODE_HW_DETECTION_SW\n");
> @@ -1959,7 +1934,7 @@ static int omap_nand_probe(struct platform_device *pdev)
>  		nand_chip->ecc.bytes		= 13;
>  		nand_chip->ecc.strength		= 8;
>  		nand_chip->ecc.hwctl		= omap3_enable_hwecc_bch;
> -		nand_chip->ecc.correct		= omap3_correct_data_bch;
> +		info->nand.ecc.correct		= nand_bch_correct_data;
>  		nand_chip->ecc.calculate	= omap3_calculate_ecc_bch8;
>  		/* define custom ECC layout */
>  		ecclayout->eccbytes		= nand_chip->ecc.bytes *
> @@ -1969,10 +1944,11 @@ static int omap_nand_probe(struct platform_device *pdev)
>  		ecclayout->oobfree->offset	= ecclayout->eccpos[0] +
>  							ecclayout->eccbytes;
>  		/* software bch library is used for locating errors */
> -		info->bch = init_bch(nand_chip->ecc.bytes,
> -					nand_chip->ecc.strength,
> -					OMAP_ECC_BCH8_POLYNOMIAL);
> -		if (!info->bch) {
> +		info->nand.ecc.priv		= nand_bch_init(mtd,
> +							info->nand.ecc.size,
> +							info->nand.ecc.bytes,
> +							&info->nand.ecc.layout);
> +		if (!info->nand.ecc.priv) {
>  			pr_err("nand: error: unable to use s/w BCH library\n");
>  			err = -EINVAL;
>  			goto out_release_mem_region;
> @@ -2023,7 +1999,6 @@ static int omap_nand_probe(struct platform_device *pdev)
>  	}
>  
>  	/* populate remaining info for custom ecc layout */
> -	pr_info("%s: using custom ecc layout\n", DRIVER_NAME);
>  	ecclayout->oobfree->length = mtd->oobsize - BADBLOCK_MARKER_LENGTH
>  						- ecclayout->eccbytes;
>  	if (!(nand_chip->options & NAND_BUSWIDTH_16))
> @@ -2061,7 +2036,12 @@ out_release_mem_region:
>  		free_irq(info->gpmc_irq_fifo, info);
>  	release_mem_region(info->phys_base, info->mem_size);
>  out_free_info:
> -	omap3_free_bch(&info->mtd);
> +#ifdef CONFIG_MTD_NAND_ECC_BCH
> +	if (info->nand.ecc.priv) {
> +		nand_bch_free(info->nand.ecc.priv);
> +		info->nand.ecc.priv = NULL;
> +	}
> +#endif
>  	kfree(info);
>  
>  	return err;
> @@ -2072,8 +2052,12 @@ static int omap_nand_remove(struct platform_device *pdev)
>  	struct mtd_info *mtd = platform_get_drvdata(pdev);
>  	struct omap_nand_info *info = container_of(mtd, struct omap_nand_info,
>  							mtd);
> -	omap3_free_bch(&info->mtd);
> -
> +#ifdef CONFIG_MTD_NAND_ECC_BCH
> +	if (info->nand.ecc.priv) {
> +		nand_bch_free(info->nand.ecc.priv);
> +		info->nand.ecc.priv = NULL;
> +	}
> +#endif
>  	if (info->dma)
>  		dma_release_channel(info->dma);
>  
> -- 
> 1.8.1
> 

-- 
balbi

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