RE: [PATCH v5 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 v6 of the patch based on your comments.

Thanks.
Jane

> -----Original Message-----
> From: Boris Brezillon [mailto:boris.brezillon@xxxxxxxxxxx]
> Sent: Thursday, May 10, 2018 5:03 AM
> To: Wan, Jane (Nokia - US/Sunnyvale) <jane.wan@xxxxxxxxx>
> Cc: miquel.raynal@xxxxxxxxxxx; dwmw2@xxxxxxxxxxxxx;
> computersforpeace@xxxxxxxxx; richard@xxxxxx; marek.vasut@xxxxxxxxx;
> yamada.masahiro@xxxxxxxxxxxxx; prabhakar.kushwaha@xxxxxxx;
> shawnguo@xxxxxxxxxx; jagdish.gediya@xxxxxxx;
> shreeya.patel23498@xxxxxxxxx; linux-mtd@xxxxxxxxxxxxxxxxxxx; linux-
> kernel@xxxxxxxxxxxxxxx; Bos, Ties (Nokia - US/Sunnyvale) <ties.bos@xxxxxxxxx>
> Subject: Re: [PATCH v5 2/2] mtd: rawnand: use bit-wise majority to recover the
> contents of ONFI parameter
> 
> Hi Jane,
> 
> Subject prefix should be "[PATCH v5] ...", the 2/2 is no longer valid since you only
> have one patch here.
> 
> On Wed,  9 May 2018 19:46:40 -0700
> Jane Wan <Jane.Wan@xxxxxxxxx> 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@xxxxxxxxx>
> > ---
> 
> There should be a changelog here describing what has changed in each version
> of the patch.

[Jane] Added the changelogs in v6.

> 
> >  drivers/mtd/nand/raw/nand_base.c |   46
> +++++++++++++++++++++++++++++++++-----
> >  1 file changed, 41 insertions(+), 5 deletions(-)
> >
> > diff --git a/drivers/mtd/nand/raw/nand_base.c
> > b/drivers/mtd/nand/raw/nand_base.c
> > index 72f3a89..a7c2507 100644
> > --- a/drivers/mtd/nand/raw/nand_base.c
> > +++ b/drivers/mtd/nand/raw/nand_base.c
> > @@ -5086,6 +5086,34 @@ static int
> nand_flash_detect_ext_param_page(struct nand_chip *chip,
> >  	return ret;
> >  }
> >
> > +#define GET_BIT(bit, val)   (((val) >> (bit)) & 0x01)
> 
> Not sure we need that macro, see below.

[Jane] Removed.

> 
> > +
> > +/*
> > + * Recover data with bit-wise majority  */ static void
> > +nand_bit_wise_majority(const void **srcbufs,
> > +				   void *dstbuf,
> > +				   unsigned int nbufs,
> > +				   unsigned int bufsize)
> 
> I'd prefer to have nbufs just after srcbufs and named nsrcbufs:
> 
> static void nand_bit_wise_majority(const void **srcbufs,
> 				   unsigned int nsrcbufs,
> 				   void *dstbuf,
> 				   unsigned int bufsize)

[Jane] changed as above in v6.

> 
> > +{
> > +	int i, j, k;
> > +	u8 v, m;
> > +	u8 *p;
> > +
> > +	p = *(u8 **)srcbufs;
> 
> Nope, I'd like to support the cases where srcbufs are not contiguous, so that
> does not work.

[Jane] Changed as you suggested to support non-contiguous srcbufs.

> 
> > +	for (i = 0; i < bufsize; i++) {
> > +		v = 0;
> 
> You can declare the v variable here, since its scope is limited to the for loop.
> BTW, v, m, can't we pick better names? I guess v is for val, but I'm not even sure
> what m stands for.

[Jane] changed the variables to cnt and val in v6.  The "m" was for majority, now changed to cnt (counts for 1s).

> 
> > +		for (j = 0; j < 8; j++) {
> > +			m = 0;
> > +			for (k = 0; k < nbufs; k++)
> > +				m += GET_BIT(j, p[k*bufsize + i]);
> 
> 			for (k = 0; k < nbufs; k++) {
> 				const u8 *srcbuf = srcbufs[j];
> 
> 				if (srcbuf[i] & BIT(k))
> 					m++;
> 			}
> 
> > +			if (m > nbufs/2)
> 
> Space between operands and operators please
> 
> 			if (m > nbufs / 2)

[Jane]  Changed as suggested in v6.  Thanks.

> 
> > +				v |= BIT(j);
> > +		}
> > +		((u8 *)dstbuf)[i] = v;
> > +	}
> > +}
> > +
> >  /*
> >   * Check if the NAND chip is ONFI compliant, returns 1 if it is, 0 otherwise.
> >   */
> > @@ -5102,7 +5130,7 @@ 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 +5141,29 @@ 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) {
> 
> 		const void *srcbufs[3] = {p, p + 1, p + 2};
> 
> > -		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");
> > +		nand_bit_wise_majority((const void **)&p, p, 3, sizeof(*p));
> 
> 		nand_bit_wise_majority(srcbufs, ARRAY_SIZE(srcbufs), p,
> 				       sizeof(*p))

[Jane]  Changed in v6.  Thanks.

> 
> > +		if (onfi_crc16(ONFI_CRC_BASE, (u8 *)p, 254) !=
> > +				le16_to_cpu(p->crc)) {
> > +			pr_err("ONFI parameter recovery failed, aborting\n");
> > +			goto free_onfi_param_page;
> > +		}
> >  	}
> >
> >  	/* Check version */
> 
> Thanks,
> 
> Boris