linux-kernel - Re: [PATCH 19/39] mtd: nand: denali: perform erased check against raw transferred page

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Date:   Sun, 27 Nov 2016 17:12:13 +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 19/39] mtd: nand: denali: perform erased check against
 raw transferred page

On Sun, 27 Nov 2016 03:06:05 +0900
Masahiro Yamada <yamada.masahiro@...ionext.com> wrote:

> The erased page check must be done against the raw transferred data.
> The current first call of is_erase() is against the data after ECC
> correction.  I saw cases where not all of the data in the page are
> 0xFF after they are manipulated by the ECC correction engine.

Hm, that's surprising. Usually ECC engines leaves data unchanged when
uncorrectable errors are detected. Do you have examples where this
happens? How did you trigger this case?

> 
> Signed-off-by: Masahiro Yamada <yamada.masahiro@...ionext.com>
> ---
> 
>  drivers/mtd/nand/denali.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/mtd/nand/denali.c b/drivers/mtd/nand/denali.c
> index f035dac..ae44c01 100644
> --- a/drivers/mtd/nand/denali.c
> +++ b/drivers/mtd/nand/denali.c
> @@ -1168,6 +1168,7 @@ static int denali_read_page(struct mtd_info *mtd, struct nand_chip *chip,
>  		INTR_STATUS__DMA_CMD_COMP | INTR_STATUS__ECC_UNCOR_ERR :
>  		INTR_STATUS__ECC_TRANSACTION_DONE | INTR_STATUS__ECC_ERR;
>  	bool check_erased_page = false;
> +	int ret;
>  
>  	if (page != denali->page) {
>  		dev_err(denali->dev,
> @@ -1206,7 +1207,9 @@ static int denali_read_page(struct mtd_info *mtd, struct nand_chip *chip,
>  		 * error.
>  		 */
>  
> -		read_oob_data(mtd, chip->oob_poi, denali->page);
> +		ret = denali_read_page_raw(mtd, chip, buf, 1, denali->page);
> +		if (ret < 0)
> +			return ret;
>  
>  		/* check ECC failures that may have occurred on erased pages */
>  		if (!is_erased(buf, mtd->writesize) ||