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

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Message-ID: <20230412094651.39f4dbf6@xps-13>
Date:   Wed, 12 Apr 2023 09:47:02 +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 again,

miquel.raynal@...tlin.com wrote on Wed, 12 Apr 2023 09:44:00 +0200:

> 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);  

Should use 0xff instead of 0x00, that's the default state of a NAND
cell.

And also this memset should be conditioned to 'oob_required' I
guess?

> 
> 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


Thanks,
Miquèl