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Date:   Wed, 29 Mar 2023 11:00:54 +0200
From:   Miquel Raynal <miquel.raynal@bootlin.com>
To:     Arseniy Krasnov <avkrasnov@sberdevices.ru>
Cc:     Tudor Ambarus <tudor.ambarus@linaro.org>,
        Liang Yang <liang.yang@amlogic.com>,
        Richard Weinberger <richard@nod.at>,
        Vignesh Raghavendra <vigneshr@ti.com>,
        Neil Armstrong <neil.armstrong@linaro.org>,
        Kevin Hilman <khilman@baylibre.com>,
        Jerome Brunet <jbrunet@baylibre.com>,
        Martin Blumenstingl <martin.blumenstingl@googlemail.com>,
        Jianxin Pan <jianxin.pan@amlogic.com>,
        Yixun Lan <yixun.lan@amlogic.com>,
        <linux-mtd@lists.infradead.org>,
        <linux-arm-kernel@lists.infradead.org>,
        <linux-amlogic@lists.infradead.org>,
        <linux-kernel@vger.kernel.org>, <kernel@sberdevices.ru>,
        <oxffffaa@gmail.com>
Subject: Re: [PATCH v2] mtd: rawnand: meson: fix bitmask for length in
 command word
Message-ID: <20230329110054.68455418@xps-13>
In-Reply-To: <c110bd0f-f25a-a74a-07cb-4c3fdb8ef306@sberdevices.ru>
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        <447abc1b-b4a3-5848-c99a-ecbff11486fe@linaro.org>
        <c110bd0f-f25a-a74a-07cb-4c3fdb8ef306@sberdevices.ru>
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Hi Arseniy,

avkrasnov@sberdevices.ru wrote on Wed, 29 Mar 2023 11:33:38 +0300:

> On 29.03.2023 11:09, Tudor Ambarus wrote:
> >=20
> >=20
> > On 3/29/23 08:47, Arseniy Krasnov wrote: =20
> >> Valid mask is 0x3FFF, without this patch the following problems were
> >> found:
> >>
> >> 1) [    0.938914] Could not find a valid ONFI parameter page, trying
> >>                   bit-wise majority to recover it
> >>    [    0.947384] ONFI parameter recovery failed, aborting
> >>
> >> 2) Read with disabled ECC mode was broken.
> >>
> >> Fixes: 8fae856c5350 ("mtd: rawnand: meson: add support for Amlogic NAN=
D flash controller")
> >> Cc: <Stable@vger.kernel.org>
> >> Signed-off-by: Arseniy Krasnov <AVKrasnov@sberdevices.ru>
> >> ---
> >>  drivers/mtd/nand/raw/meson_nand.c | 6 +++---
> >>  1 file changed, 3 insertions(+), 3 deletions(-)
> >>
> >> diff --git a/drivers/mtd/nand/raw/meson_nand.c b/drivers/mtd/nand/raw/=
meson_nand.c
> >> index a28574c00900..074e14225c06 100644
> >> --- a/drivers/mtd/nand/raw/meson_nand.c
> >> +++ b/drivers/mtd/nand/raw/meson_nand.c
> >> @@ -280,7 +280,7 @@ static void meson_nfc_cmd_access(struct nand_chip =
*nand, int raw, bool dir,
> >> =20
> >>  	if (raw) {
> >>  		len =3D mtd->writesize + mtd->oobsize;
> >> -		cmd =3D (len & GENMASK(5, 0)) | scrambler | DMA_DIR(dir);
> >> +		cmd =3D (len & GENMASK(13, 0)) | scrambler | DMA_DIR(dir); =20
> >=20
> > What happens when len > GENMASK(13, 0)? Do you check this somewhere? =20
>=20
> 'len' will be trimmed. I'm not sure that this case is possible here, beca=
use GENMASK(13, 0)
> is hardware limit for this NAND controller, so 'writesize' and 'oobsize' =
will be initialized
> to fit this value. Moreover GENMASK(13, 0) is 16Kb - i think it is big en=
ough for single
> read. Also i'm not sure that it is good approach to check 'len' here - we=
 are in the middle
> of NAND read processing.

No, you should check the page size will not exceed this limit in the
attach hook, likely.

You should also refuse exec_op operations with a data length bigger
than 16k (either with a manual check in your own parser or just by
providing the max size to the parser table, depending on what's used).

>=20
> >=20
> > Please introduce a macro/field for GENMASK(13, 0), having such mask
> > scattered along the code looks hackish and doesn't help readability.
> > You'll get to use FIELD_PREP as well. =20
>=20
> Ack, i'll do it in v3
>=20
> Thanks, Arseniy
>=20
> >  =20
> >>  		writel(cmd, nfc->reg_base + NFC_REG_CMD);
> >>  		return;
> >>  	}
> >> @@ -544,7 +544,7 @@ static int meson_nfc_read_buf(struct nand_chip *na=
nd, u8 *buf, int len)
> >>  	if (ret)
> >>  		goto out;
> >> =20
> >> -	cmd =3D NFC_CMD_N2M | (len & GENMASK(5, 0));
> >> +	cmd =3D NFC_CMD_N2M | (len & GENMASK(13, 0));
> >>  	writel(cmd, nfc->reg_base + NFC_REG_CMD);
> >> =20
> >>  	meson_nfc_drain_cmd(nfc);
> >> @@ -568,7 +568,7 @@ static int meson_nfc_write_buf(struct nand_chip *n=
and, u8 *buf, int len)
> >>  	if (ret)
> >>  		return ret;
> >> =20
> >> -	cmd =3D NFC_CMD_M2N | (len & GENMASK(5, 0));
> >> +	cmd =3D NFC_CMD_M2N | (len & GENMASK(13, 0));
> >>  	writel(cmd, nfc->reg_base + NFC_REG_CMD);
> >> =20
> >>  	meson_nfc_drain_cmd(nfc); =20


Thanks,
Miqu=C3=A8l