Re: Issue in oamp nand driver with 32-bit reads in prefetch mode

[Artem Bityutskiy <dedekind1@gmail.com>]

On Thu, 2009-12-31 at 17:50 +0530, Vimal Singh wrote:
> There is a bug in nand prefetch read routine, which comes into effect
> only if nand device is a 16-bit device (as we have in zoom boards).
> This bug is effective only with below combination of conditions:
> 1. nand deivce, in use, is a 16 bit device
> 2. nand driver supports 'subpage' read
> 3. SW ECC is in use
> 
> This was not seen old  kernel (ex: .23), because when, in early days,
> we tested this (nand prefetch read in LDP boards) there was no
> 'subpage read' support.
> Later when we had subpage read in (.27) kernel, we had hw ecc enabled
> always in our internal tree. So, we missed this bug.
> 
> Here is a patch to fix this issue:
> 
> diff --git a/drivers/mtd/nand/omap2.c b/drivers/mtd/nand/omap2.c
> index 1bb799f..75004fe 100644
> --- a/drivers/mtd/nand/omap2.c
> +++ b/drivers/mtd/nand/omap2.c
> @@ -295,11 +295,14 @@ static void omap_read_buf_pref(struct
>  	u32 *p = (u32 *)buf;
> 
>  	/* take care of subpage reads */
> -	for (; len % 4 != 0; ) {
> -		*buf++ = __raw_readb(info->nand.IO_ADDR_R);
> -		len--;
> +	if (len % 4) {
> +		if (info->nand.options & NAND_BUSWIDTH_16)
> +			omap_read_buf16(mtd, buf, len % 4);
> +		else
> +			omap_read_buf8(mtd, buf, len % 4);
> +		p = (u32 *) (buf + len % 4);
> +		len -= len % 4;
>  	}
> -	p = (u32 *) buf;
> 
>  	/* configure and start prefetch transfer */
>  	ret = gpmc_prefetch_enable(info->gpmc_cs, 0x0, len, 0x0);

Pushed this patch to my l2-mtd-2.6.git/dunno.

-- 
Best Regards,
Artem Bityutskiy (Артём Битюцкий)

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