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

[RogerCC.Lin <rogercc.lin-NuS5LvNUpcJWk0Htik3J/w@public.gmane.org>]

On Wed, 2016-08-31 at 10:09 +0200, Boris Brezillon wrote:
> On Tue, 30 Aug 2016 20:35:47 +0800
> RogerCC Lin <rogercc.lin-NuS5LvNUpcJWk0Htik3J/w@public.gmane.org> wrote:
> 
> > From: RogerCC Lin <rogercc.lin-NuS5LvNUpcJWk0Htik3J/w@public.gmane.org>
> > 
> > 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-NuS5LvNUpcJWk0Htik3J/w@public.gmane.org>
> > ---
> >  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.

Of course, please apply the patch with 'i / 4', 
thank you.

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