linux-kernel - Re: [PATCH 09/39] mtd: nand: denali: fix erased page check code

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Date:   Sun, 27 Nov 2016 16:21:29 +0100
From:   Boris Brezillon <boris.brezillon@...e-electrons.com>
To:     Masahiro Yamada <yamada.masahiro@...ionext.com>
Cc:     linux-mtd@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Marek Vasut <marek.vasut@...il.com>,
        Brian Norris <computersforpeace@...il.com>,
        Richard Weinberger <richard@....at>,
        David Woodhouse <dwmw2@...radead.org>,
        Cyrille Pitchen <cyrille.pitchen@...el.com>
Subject: Re: [PATCH 09/39] mtd: nand: denali: fix erased page check code

On Sun, 27 Nov 2016 03:05:55 +0900
Masahiro Yamada <yamada.masahiro@...ionext.com> wrote:

> Currently, is_erased() is called against "buf" twice, so the second
> call is meaningless.  The second one should be checked against
> chip->oob_poi.
> 

IMO, patch 9 to 12 should be squashed in a single patch. All you're
doing in these patch is fixing the check_erased_page logic.

You can describe the different broken thing in the commit message, but
splitting things as you do does not help much.

Also, please have at nand_check_erased_ecc_chunk() [1] instead of using
a private method (is_erased()) to check if the page is erased.
With this method you get bitflips in erased pages correction for free.

[1]http://lxr.free-electrons.com/source/drivers/mtd/nand/nand_base.c#L1212

> Signed-off-by: Masahiro Yamada <yamada.masahiro@...ionext.com>
> ---
> 
>  drivers/mtd/nand/denali.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/mtd/nand/denali.c b/drivers/mtd/nand/denali.c
> index cbc7f75..753e9a02 100644
> --- a/drivers/mtd/nand/denali.c
> +++ b/drivers/mtd/nand/denali.c
> @@ -1160,7 +1160,7 @@ static int denali_read_page(struct mtd_info *mtd, struct nand_chip *chip,
>  		if (check_erased_page) {
>  			if (!is_erased(buf, mtd->writesize))
>  				mtd->ecc_stats.failed++;
> -			if (!is_erased(buf, mtd->oobsize))
> +			if (!is_erased(chip->oob_poi, mtd->oobsize))
>  				mtd->ecc_stats.failed++;
>  		}
>  	}