linux-kernel - Re: [PATCH 2/2] Use bit-wise majority to recover the contents of ONFI parameter

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Date:   Wed, 2 May 2018 12:31:37 +0200
From:   Boris Brezillon <boris.brezillon@...tlin.com>
To:     Jane Wan <Jane.Wan@...ia.com>
Cc:     dwmw2@...radead.org, computersforpeace@...il.com,
        ties.bos@...ia.com, linux-mtd@...ts.infradead.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] Use bit-wise majority to recover the contents of
 ONFI parameter

On Wed, 2 May 2018 12:25:45 +0200
Boris Brezillon <boris.brezillon@...tlin.com> wrote:

> Hi Jane,
> 
> On Thu, 26 Apr 2018 17:19:56 -0700
> Jane Wan <Jane.Wan@...ia.com> wrote:
> 
> > Signed-off-by: Jane Wan <Jane.Wan@...ia.com>
> > ---
> >  drivers/mtd/nand/nand_base.c |   35 +++++++++++++++++++++++++++++++----
> >  1 file changed, 31 insertions(+), 4 deletions(-)
> > 
> > diff --git a/drivers/mtd/nand/nand_base.c b/drivers/mtd/nand/nand_base.c
> > index c2e1232..161b523 100644
> > --- a/drivers/mtd/nand/nand_base.c
> > +++ b/drivers/mtd/nand/nand_base.c
> > @@ -3153,8 +3153,10 @@ static int nand_flash_detect_onfi(struct mtd_info *mtd, struct nand_chip *chip,
> >  					int *busw)
> >  {
> >  	struct nand_onfi_params *p = &chip->onfi_params;
> > -	int i, j;
> > -	int val;
> > +	int i, j, k, len, val;
> > +	uint8_t copy[3][256], v8;
> > +
> > +	len = (sizeof(*p) > 256) ? 256 : sizeof(*p);
> >  
> >  	/* Try ONFI for unknown chip or LP */
> >  	chip->cmdfunc(mtd, NAND_CMD_READID, 0x20, -1);
> > @@ -3170,11 +3172,36 @@ static int nand_flash_detect_onfi(struct mtd_info *mtd, struct nand_chip *chip,
> >  				le16_to_cpu(p->crc)) {
> >  			break;
> >  		}
> > +		pr_err("CRC of parameter page %d is not valid\n", i);
> > +		for (j = 0; j < len; j++)
> > +			copy[i][j] = ((uint8_t *)p)[j];
> >  	}
> >  
> >  	if (i == 3) {
> > -		pr_err("Could not find valid ONFI parameter page; aborting\n");
> > -		return 0;
> > +		pr_err("Could not find valid ONFI parameter page\n");
> > +		pr_info("Recover ONFI parameters with bit-wise majority\n");
> > +		for (j = 0; j < len; j++) {
> > +			if (copy[0][j] == copy[1][j] ||
> > +			    copy[0][j] == copy[2][j]) {
> > +				((uint8_t *)p)[j] = copy[0][j];
> > +			} else if (copy[1][j] == copy[2][j]) {
> > +				((uint8_t *)p)[j] = copy[1][j];
> > +			} else {
> > +				((uint8_t *)p)[j] = 0;
> > +				for (k = 0; k < 8; k++) {
> > +					v8 = (copy[0][j] >> k) & 0x1;
> > +					v8 += (copy[1][j] >> k) & 0x1;
> > +					v8 += (copy[2][j] >> k) & 0x1;
> > +					if (v8 > 1)
> > +						((uint8_t *)p)[j] |= (1 << k);
> > +				}
> > +			}
> > +		}  
> 
> I'd like this bit-wise majority algorithm to be generic and moved to
> nand_base.c, because we might want to do the same in the core and make
> it work for any number of repetitions of the PARAM page.

Never mind, I thought you were implementing that in the FSL IFC driver,
but you're actually modifying the core.