Re: [PATCH] mtd: nand: tango: Update ecc_stats.corrected

[Boris Brezillon <boris.brezillon@free-electrons.com>]

On Fri, 12 May 2017 17:34:01 +0200
Marc Gonzalez <marc_gonzalez@sigmadesigns.com> wrote:

> According to Boris, some user-space tools expect MTD drivers to
> update ecc_stats.corrected, and it's better to provide a lower
> bound than to provide no information at all.
> 
> Reported-by: Pavel Machek <pavel@ucw.cz>
> Signed-off-by: Marc Gonzalez <marc_gonzalez@sigmadesigns.com>

Applied to nand/fixes after changing decode_error_report() prototype
and adding Fixes+Cc-stable tags (as discussed on IRC).

Thanks,

Boris

> ---
> NB: this patch is based on 4.9; if it looks good, I'll rebase
> it on v4.12-rc1 next week.
> ---
>  drivers/mtd/nand/tango_nand.c | 21 ++++++++++++++-------
>  1 file changed, 14 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/mtd/nand/tango_nand.c b/drivers/mtd/nand/tango_nand.c
> index 4a5e948c62df..471348462e42 100644
> --- a/drivers/mtd/nand/tango_nand.c
> +++ b/drivers/mtd/nand/tango_nand.c
> @@ -55,10 +55,10 @@
>   * byte 1 for other packets in the page (PKT_N, for N > 0)
>   * ERR_COUNT_PKT_N is the max error count over all but the first packet.
>   */
> -#define DECODE_OK_PKT_0(v)	((v) & BIT(7))
> -#define DECODE_OK_PKT_N(v)	((v) & BIT(15))
>  #define ERR_COUNT_PKT_0(v)	(((v) >> 0) & 0x3f)
>  #define ERR_COUNT_PKT_N(v)	(((v) >> 8) & 0x3f)
> +#define DECODE_FAIL_PKT_0(v)	(((v) & BIT(7)) == 0)
> +#define DECODE_FAIL_PKT_N(v)	(((v) & BIT(15)) == 0)
>  
>  /* Offsets relative to pbus_base */
>  #define PBUS_CS_CTRL	0x83c
> @@ -193,6 +193,8 @@ static int check_erased_page(struct nand_chip *chip, u8 *buf)
>  						  chip->ecc.strength);
>  		if (res < 0)
>  			mtd->ecc_stats.failed++;
> +		else
> +			mtd->ecc_stats.corrected += res;
>  
>  		bitflips = max(res, bitflips);
>  		buf += pkt_size;
> @@ -202,9 +204,10 @@ static int check_erased_page(struct nand_chip *chip, u8 *buf)
>  	return bitflips;
>  }
>  
> -static int decode_error_report(struct tango_nfc *nfc)
> +static int decode_error_report(struct nand_chip *chip, struct tango_nfc *nfc)
>  {
>  	u32 status, res;
> +	struct mtd_info *mtd = nand_to_mtd(chip);
>  
>  	status = readl_relaxed(nfc->reg_base + NFC_XFER_STATUS);
>  	if (status & PAGE_IS_EMPTY)
> @@ -212,10 +215,14 @@ static int decode_error_report(struct tango_nfc *nfc)
>  
>  	res = readl_relaxed(nfc->mem_base + ERROR_REPORT);
>  
> -	if (DECODE_OK_PKT_0(res) && DECODE_OK_PKT_N(res))
> -		return max(ERR_COUNT_PKT_0(res), ERR_COUNT_PKT_N(res));
> +	if (DECODE_FAIL_PKT_0(res) || DECODE_FAIL_PKT_N(res))
> +		return -EBADMSG;
> +
> +	/* ERR_COUNT_PKT_N is max, not sum, but that's all we have */
> +	mtd->ecc_stats.corrected +=
> +		ERR_COUNT_PKT_0(res) + ERR_COUNT_PKT_N(res);
>  
> -	return -EBADMSG;
> +	return max(ERR_COUNT_PKT_0(res), ERR_COUNT_PKT_N(res));
>  }
>  
>  static void tango_dma_callback(void *arg)
> @@ -280,7 +287,7 @@ static int tango_read_page(struct mtd_info *mtd, struct nand_chip *chip,
>  	if (err)
>  		return err;
>  
> -	res = decode_error_report(nfc);
> +	res = decode_error_report(chip, nfc);
>  	if (res < 0) {
>  		chip->ecc.read_oob_raw(mtd, chip, page);
>  		res = check_erased_page(chip, buf);