Re: [PATCH v4 1/2] mtd: nand: fix generating over-boundary ECC data when writing

[Boris Brezillon <boris.brezillon@free-electrons.com>]

On Tue, 30 Aug 2016 20:35:47 +0800
RogerCC Lin <rogercc.lin@mediatek.com> wrote:

> From: RogerCC Lin <rogercc.lin@mediatek.com>
> 
> When mtk_ecc_encode() is writing the ECC parity data to the OOB
> region,because each register is 4 bytes in length,but the len's unit is
> in bytes,the operation in the for loop will cross the ECC's boundary.
> 
> Signed-off-by: RogerCC Lin <rogercc.lin@mediatek.com>
> ---
>  drivers/mtd/nand/mtk_ecc.c |   12 ++++++++----
>  1 files changed, 8 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/mtd/nand/mtk_ecc.c b/drivers/mtd/nand/mtk_ecc.c
> index 25a4fbd..495538e 100644
> --- a/drivers/mtd/nand/mtk_ecc.c
> +++ b/drivers/mtd/nand/mtk_ecc.c
> @@ -366,7 +366,8 @@ int mtk_ecc_encode(struct mtk_ecc *ecc, struct mtk_ecc_config *config,
>  		   u8 *data, u32 bytes)
>  {
>  	dma_addr_t addr;
> -	u32 *p, len, i;
> +	u8 *p;
> +	u32 len, i, val;
>  	int ret = 0;
>  
>  	addr = dma_map_single(ecc->dev, data, bytes, DMA_TO_DEVICE);
> @@ -392,11 +393,14 @@ int mtk_ecc_encode(struct mtk_ecc *ecc, struct mtk_ecc_config *config,
>  
>  	/* Program ECC bytes to OOB: per sector oob = FDM + ECC + SPARE */
>  	len = (config->strength * ECC_PARITY_BITS + 7) >> 3;
> -	p = (u32 *)(data + bytes);
> +	p = data + bytes;
>  
>  	/* write the parity bytes generated by the ECC back to the OOB region */
> -	for (i = 0; i < len; i++)
> -		p[i] = readl(ecc->regs + ECC_ENCPAR(i));
> +	for (i = 0; i < len; i++) {
> +		if ((i % 4) == 0)
> +			val = readl(ecc->regs + ECC_ENCPAR(i >> 2));

I'm nitpicking, but I'd prefer to have 'i / 4' instead of 'i >> 2' to
be consistent with the 'i % 4' operation, and I also find it clearer.

If you agree, I can do this change while applying the patch, no need to
resend.

> +		p[i] = (val >> ((i % 4) * 8)) & 0xff;
> +	}
>  timeout:
>  
>  	dma_unmap_single(ecc->dev, addr, bytes, DMA_TO_DEVICE);