Re: i.MX25 NFC with 8 bit ecc strength

[Baruch Siach <baruch@tkos.co.il>]

Hi Uwe,

On Tue, Apr 21, 2015 at 09:39:36AM +0200, Uwe Kleine-König wrote:
> While understanding the problem I produced the following (untested)
> patch:

I intend to use this patch as part of a series fixing the large oob issue. Can 
you add your SoB please?

Thanks,
baruch

> diff --git a/drivers/mtd/nand/mxc_nand.c b/drivers/mtd/nand/mxc_nand.c
> index dca63a70e783..fc835d352e1c 100644
> --- a/drivers/mtd/nand/mxc_nand.c
> +++ b/drivers/mtd/nand/mxc_nand.c
> @@ -807,32 +807,49 @@ static void mxc_nand_select_chip_v2(struct mtd_info *mtd, int chip)
>  }
>  
>  /*
> - * Function to transfer data to/from spare area.
> + * The controller splits a page into data chunks of 512 bytes + partial oob.
> + * There are writesize / 512 such chunks, the size of the partial oob parts is
> + * oobsize / #chunks rounded down to a multiple of 2. The last oob chunk then
> + * contains additionally the byte lost by rounding (if any).
> + * This function handles the needed shuffling between host->data_buf (which
> + * holds a page in natural order, i.e. writesize bytes data + oobsize bytes
> + * spare) and the NFC buffer.
>   */
>  static void copy_spare(struct mtd_info *mtd, bool bfrom)
>  {
>  	struct nand_chip *this = mtd->priv;
>  	struct mxc_nand_host *host = this->priv;
>  	u16 i, j;
> -	u16 n = mtd->writesize >> 9;
> +
> +	u16 num_chunks = mtd->writesize / 512;
> +
>  	u8 *d = host->data_buf + mtd->writesize;
>  	u8 __iomem *s = host->spare0;
> -	u16 t = host->devtype_data->spare_len;
> +	u16 sparebuf_size = host->devtype_data->spare_len;
>  
> -	j = (mtd->oobsize / n >> 1) << 1;
> +	/* size of oob chunk for all but possibly the last one */
> +	oob_chunk_size = (mtd->oobsize / num_chunks >> 1) << 1;
>  
>  	if (bfrom) {
> -		for (i = 0; i < n - 1; i++)
> -			memcpy32_fromio(d + i * j, s + i * t, j);
> +		for (i = 0; i < num_chunks - 1; i++)
> +			memcpy32_fromio(d + i * oob_chunk_size,
> +					s + i * sparebuf_size,
> +					oob_chunk_size);
>  
>  		/* the last section */
> -		memcpy32_fromio(d + i * j, s + i * t, mtd->oobsize - i * j);
> +		memcpy32_fromio(d + i * oob_chunk_size,
> +				s + i * sparebuf_size,
> +				mtd->oobsize - i * oob_chunk_size);
>  	} else {
> -		for (i = 0; i < n - 1; i++)
> -			memcpy32_toio(&s[i * t], &d[i * j], j);
> +		for (i = 0; i < num_chunks - 1; i++)
> +			memcpy32_toio(&s[i * sparebuf_size],
> +				      &d[i * oob_chunk_size],
> +				      oob_chunk_size);
>  
>  		/* the last section */
> -		memcpy32_toio(&s[i * t], &d[i * j], mtd->oobsize - i * j);
> +		memcpy32_toio(&s[oob_chunk_size * sparebuf_size],
> +			      &d[i * oob_chunk_size],
> +			      mtd->oobsize - i * oob_chunk_size);
>  	}
>  }

-- 
     http://baruch.siach.name/blog/                  ~. .~   Tk Open Systems
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   - baruch@tkos.co.il - tel: +972.2.679.5364, http://www.tkos.co.il -