linux-kernel - Re: [PATCH v3 2/2] mtd: rawnand: fsl_ifc: use bit-wise majority to recover the contents of ONFI parameter

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Message-ID: <20180508110858.7b1432f5@bbrezillon>
Date:   Tue, 8 May 2018 11:08:58 +0200
From:   Boris Brezillon <boris.brezillon@...tlin.com>
To:     Jane Wan <Jane.Wan@...ia.com>
Cc:     miquel.raynal@...tlin.com, dwmw2@...radead.org,
        computersforpeace@...il.com, richard@....at, marek.vasut@...il.com,
        yamada.masahiro@...ionext.com, prabhakar.kushwaha@....com,
        shawnguo@...nel.org, jagdish.gediya@....com,
        shreeya.patel23498@...il.com, linux-mtd@...ts.infradead.org,
        linux-kernel@...r.kernel.org, ties.bos@...ia.com
Subject: Re: [PATCH v3 2/2] mtd: rawnand: fsl_ifc: use bit-wise majority to
 recover the contents of ONFI parameter

On Mon,  7 May 2018 09:34:15 -0700
Jane Wan <Jane.Wan@...ia.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@...ia.com>

I never received patch 1 of this series. When you fix something in a
commit, please resend the whole patchset, even if other patches haven't
changed.

> ---
>  drivers/mtd/nand/raw/nand_base.c |   41 ++++++++++++++++++++++++++++++--------
>  1 file changed, 33 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/mtd/nand/raw/nand_base.c b/drivers/mtd/nand/raw/nand_base.c
> index 72f3a89..48f2dec 100644
> --- a/drivers/mtd/nand/raw/nand_base.c
> +++ b/drivers/mtd/nand/raw/nand_base.c
> @@ -5086,15 +5086,18 @@ static int nand_flash_detect_ext_param_page(struct nand_chip *chip,
>  	return ret;
>  }
>  
> +#define GET_BIT(bit, val)   (((val) >> (bit)) & 0x01)
> +
>  /*
>   * Check if the NAND chip is ONFI compliant, returns 1 if it is, 0 otherwise.
>   */
>  static int nand_flash_detect_onfi(struct nand_chip *chip)
>  {
>  	struct mtd_info *mtd = nand_to_mtd(chip);
> -	struct nand_onfi_params *p;
> +	struct nand_onfi_params *p = NULL;
>  	char id[4];
> -	int i, ret, val;
> +	int i, ret, val, pagesize;
> +	u8 *buf = NULL;
>  
>  	/* Try ONFI for unknown chip or LP */
>  	ret = nand_readid_op(chip, 0x20, id, sizeof(id));
> @@ -5102,8 +5105,9 @@ 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);
> -	if (!p)
> +	pagesize = sizeof(*p);
> +	buf = kzalloc((pagesize * 3), GFP_KERNEL);

Not sure why you have to add a new buf variable here, and pagesize is
not needed either, just use sizeof(*p) directly.

> +	if (!buf)
>  		return -ENOMEM;
>  
>  	ret = nand_read_param_page_op(chip, 0, NULL, 0);
> @@ -5113,7 +5117,8 @@ 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);
> +		p = (struct nand_onfi_params *)&buf[i*pagesize];
> +		ret = nand_read_data_op(chip, p, pagesize, true);
>  		if (ret) {
>  			ret = 0;
>  			goto free_onfi_param_page;
> @@ -5126,8 +5131,27 @@ static int nand_flash_detect_onfi(struct nand_chip *chip)
>  	}
>  
>  	if (i == 3) {
> -		pr_err("Could not find valid ONFI parameter page; aborting\n");
> -		goto free_onfi_param_page;
> +		int j, k, l;
> +		u8 v, m;
> +
> +		pr_err("Could not find valid ONFI parameter page\n");
> +		pr_info("Recover ONFI params with bit-wise majority\n");
> +		for (j = 0; j < pagesize; j++) {
> +			v = 0;
> +			for (k = 0; k < 8; k++) {
> +				m = 0;
> +				for (l = 0; l < 3; l++)
> +					m += GET_BIT(k, buf[l*pagesize + j]);
> +				if (m > 1)
> +					v |= BIT(k);
> +			}
> +			((u8 *)p)[j] = v;
> +		}

Can you move the bit-wise majority code in a separate function?

> +		if (onfi_crc16(ONFI_CRC_BASE, (uint8_t *)p, 254) !=
> +				le16_to_cpu(p->crc)) {
> +			pr_err("ONFI parameter recovery failed, aborting\n");
> +			goto free_onfi_param_page;
> +		}
>  	}
>  
>  	/* Check version */
> @@ -5220,7 +5244,8 @@ static int nand_flash_detect_onfi(struct nand_chip *chip)
>  	       sizeof(p->vendor));
>  
>  free_onfi_param_page:
> -	kfree(p);
> +	if (buf != NULL)
> +		kfree(buf);

kfree() already handles the buf == NULL case, no need to check it here.

>  	return ret;
>  }
>