[PATCH v4 2/2] mtd: rawnand: use bit-wise majority to recover the contents of ONFI parameter

[Wan, Jane (Nokia - US/Sunnyvale)]

Hi Boris,

I've sent v5 of the patch based on your comment.

Thanks.
Jane

> -----Original Message-----
> From: Boris Brezillon [mailto:boris.brezillon at bootlin.com]
> Sent: Wednesday, May 09, 2018 7:19 AM
> To: Wan, Jane (Nokia - US/Sunnyvale) <jane.wan at nokia.com>
> Cc: miquel.raynal at bootlin.com; dwmw2 at infradead.org;
> computersforpeace at gmail.com; richard at nod.at; marek.vasut at gmail.com;
> yamada.masahiro at socionext.com; prabhakar.kushwaha at nxp.com;
> shawnguo at kernel.org; jagdish.gediya at nxp.com;
> shreeya.patel23498 at gmail.com; linux-mtd at lists.infradead.org; linux-
> kernel at vger.kernel.org; Bos, Ties (Nokia - US/Sunnyvale) <ties.bos at nokia.com>
> Subject: Re: [PATCH v4 2/2] mtd: rawnand: use bit-wise majority to recover the
> contents of ONFI parameter
> 
> On Tue,  8 May 2018 14:19:54 -0700
> Jane Wan <Jane.Wan at nokia.com> wrote:
> 
> > Per ONFI specification (Rev. 4.0), if all parameter pages have invalid
> > CRC values, the bit-wise majority may be used to recover the contents
> > of the parameter pages from the parameter page copies present.
> >
> > Signed-off-by: Jane Wan <Jane.Wan at nokia.com>
> > ---
> >  drivers/mtd/nand/raw/nand_base.c |   49
> ++++++++++++++++++++++++++++++++++----
> >  1 file changed, 44 insertions(+), 5 deletions(-)
> >
> > diff --git a/drivers/mtd/nand/raw/nand_base.c
> > b/drivers/mtd/nand/raw/nand_base.c
> > index 72f3a89..dfc341c 100644
> > --- a/drivers/mtd/nand/raw/nand_base.c
> > +++ b/drivers/mtd/nand/raw/nand_base.c
> > @@ -5086,6 +5086,38 @@ static int
> nand_flash_detect_ext_param_page(struct nand_chip *chip,
> >  	return ret;
> >  }
> >
> > +#define GET_BIT(bit, val)   (((val) >> (bit)) & 0x01)
> > +
> > +/*
> > + * Recover NAND parameter page with bit-wise majority  */ static int
> > +onfi_recover_param(struct nand_onfi_params *p, int pages)
> 
> I had something more generic in mind:
> 
> static void nand_bit_wise_majority(const void **srcbufs,
> 				   void *dstbuf,
> 				   unsigned int nbufs,
> 				   unsigned int bufsize)
> {
> 	...
> }
> 
> And then you do the crc check in nand_flash_detect_onfi().
> 
> The reason I'm asking that is because I'm almost sure we'll re-use this functions
> for extended param pages, and also for vendor specific data (we already have a
> byte-wise majority check in the hynix driver, so I wouldn't be surprised if other
> vendors decided to use a bit-wise approach for some of their OTP area).

[Jane] Modified the function as suggested in v5.

> 
> > +{
> > +	int i, j, k;
> > +	u8 v, m;
> > +	u8 *buf;
> > +
> > +	buf = (u8 *)p;
> > +	for (i = 0; i < sizeof(*p); i++) {
> > +		v = 0;
> > +		for (j = 0; j < 8; j++) {
> > +			m = 0;
> > +			for (k = 0; k < pages; k++)
> > +				m += GET_BIT(j, buf[k*sizeof(*p) + i]);
> > +			if (m > pages/2)
> > +				v |= BIT(j);
> > +		}
> > +		((u8 *)p)[i] = v;
> > +	}
> > +
> > +	if (onfi_crc16(ONFI_CRC_BASE, (u8 *)p, 254) ==
> > +			le16_to_cpu(p->crc)) {
> > +		return 1;
> > +	}
> > +
> > +	return 0;
> > +}
> > +
> >  /*
> >   * Check if the NAND chip is ONFI compliant, returns 1 if it is, 0 otherwise.
> >   */
> > @@ -5102,7 +5134,7 @@ static int nand_flash_detect_onfi(struct nand_chip
> *chip)
> >  		return 0;
> >
> >  	/* ONFI chip: allocate a buffer to hold its parameter page */
> > -	p = kzalloc(sizeof(*p), GFP_KERNEL);
> > +	p = kzalloc((sizeof(*p) * 3), GFP_KERNEL);
> >  	if (!p)
> >  		return -ENOMEM;
> >
> > @@ -5113,21 +5145,28 @@ static int nand_flash_detect_onfi(struct
> nand_chip *chip)
> >  	}
> >
> >  	for (i = 0; i < 3; i++) {
> > -		ret = nand_read_data_op(chip, p, sizeof(*p), true);
> > +		ret = nand_read_data_op(chip, &p[i], sizeof(*p), true);
> >  		if (ret) {
> >  			ret = 0;
> >  			goto free_onfi_param_page;
> >  		}
> >
> > -		if (onfi_crc16(ONFI_CRC_BASE, (uint8_t *)p, 254) ==
> > +		if (onfi_crc16(ONFI_CRC_BASE, (u8 *)&p[i], 254) ==
> >  				le16_to_cpu(p->crc)) {
> > +			if (i)
> > +				memcpy(p, &p[i], sizeof(*p));
> >  			break;
> >  		}
> >  	}
> >
> >  	if (i == 3) {
> > -		pr_err("Could not find valid ONFI parameter page; aborting\n");
> > -		goto free_onfi_param_page;
> > +		pr_err("Could not find valid ONFI parameter page\n");
> > +		pr_info("Recover ONFI params with bit-wise majority\n");
> > +		ret = onfi_recover_param(p, 3);
> > +		if (ret == 0) {
> > +			pr_err("ONFI parameter recovery failed, aborting\n");
> > +			goto free_onfi_param_page;
> > +		}
> >  	}
> >
> >  	/* Check version */