linux-kernel - Re: [PATCH v1 4/5] mtd: rawnand: meson: clear OOB buffer before read

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Message-ID: <20230412094400.3c82f631@xps-13>
Date:   Wed, 12 Apr 2023 09:44:00 +0200
From:   Miquel Raynal <miquel.raynal@...tlin.com>
To:     Arseniy Krasnov <AVKrasnov@...rdevices.ru>
Cc:     Liang Yang <liang.yang@...ogic.com>,
        Richard Weinberger <richard@....at>,
        Vignesh Raghavendra <vigneshr@...com>,
        Neil Armstrong <neil.armstrong@...aro.org>,
        Kevin Hilman <khilman@...libre.com>,
        Jerome Brunet <jbrunet@...libre.com>,
        Martin Blumenstingl <martin.blumenstingl@...glemail.com>,
        Jianxin Pan <jianxin.pan@...ogic.com>,
        Yixun Lan <yixun.lan@...ogic.com>, <oxffffaa@...il.com>,
        <kernel@...rdevices.ru>, <linux-mtd@...ts.infradead.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-amlogic@...ts.infradead.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v1 4/5] mtd: rawnand: meson: clear OOB buffer before
 read

Hi Arseniy,

AVKrasnov@...rdevices.ru wrote on Wed, 12 Apr 2023 09:16:58 +0300:

> This NAND reads only few user's bytes in ECC mode (not full OOB), so

"This NAND reads" does not look right, do you mean "Subpage reads do
not retrieve all the OOB bytes,"?

> fill OOB buffer with zeroes to not return garbage from previous reads
> to user.
> Otherwise 'nanddump' utility prints something like this for just erased
> page:
> 
> ...
> 0x000007f0: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>   OOB Data: ff ff ff ff 00 00 ff ff 80 cf 22 99 cb ad d3 be
>   OOB Data: 63 27 ae 06 16 0a 2f eb bb dd 46 74 41 8e 88 6e
>   OOB Data: 38 a1 2d e6 77 d4 05 06 f2 a5 7e 25 eb 34 7c ff
>   OOB Data: 38 ea de 14 10 de 9b 40 33 16 6a cc 9d aa 2f 5e
> 
> Signed-off-by: Arseniy Krasnov <AVKrasnov@...rdevices.ru>
> ---
>  drivers/mtd/nand/raw/meson_nand.c | 5 +++++
>  1 file changed, 5 insertions(+)
> 
> diff --git a/drivers/mtd/nand/raw/meson_nand.c b/drivers/mtd/nand/raw/meson_nand.c
> index f84a10238e4d..f2f2472cb511 100644
> --- a/drivers/mtd/nand/raw/meson_nand.c
> +++ b/drivers/mtd/nand/raw/meson_nand.c
> @@ -858,9 +858,12 @@ static int meson_nfc_read_page_sub(struct nand_chip *nand,
>  static int meson_nfc_read_page_raw(struct nand_chip *nand, u8 *buf,
>  				   int oob_required, int page)
>  {
> +	struct mtd_info *mtd = nand_to_mtd(nand);
>  	u8 *oob_buf = nand->oob_poi;
>  	int ret;
>  
> +	memset(oob_buf, 0, mtd->oobsize);

I'm surprised raw reads do not read the entire OOB?

> +
>  	ret = meson_nfc_read_page_sub(nand, page, 1);
>  	if (ret)
>  		return ret;
> @@ -881,6 +884,8 @@ static int meson_nfc_read_page_hwecc(struct nand_chip *nand, u8 *buf,
>  	u8 *oob_buf = nand->oob_poi;
>  	int ret, i;
>  
> +	memset(oob_buf, 0, mtd->oobsize);
> +
>  	ret = meson_nfc_read_page_sub(nand, page, 0);
>  	if (ret)
>  		return ret;


Thanks,
Miquèl