Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
Date:   Mon, 2 Jan 2023 10:11:32 +0100
From:   Miquel Raynal <miquel.raynal@bootlin.com>
To:     Samuel Holland <samuel@sholland.org>
Cc:     Richard Weinberger <richard@nod.at>,
        Vignesh Raghavendra <vigneshr@ti.com>,
        Chen-Yu Tsai <wens@csie.org>,
        Jernej Skrabec <jernej.skrabec@gmail.com>,
        Boris Brezillon <bbrezillon@kernel.org>,
        Brian Norris <computersforpeace@gmail.com>,
        linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org,
        linux-mtd@lists.infradead.org, linux-sunxi@lists.linux.dev
Subject: Re: [PATCH 4/7] mtd: rawnand: sunxi: Fix ECC strength maximization
Message-ID: <20230102101132.66aa1a1d@xps-13>
In-Reply-To: <20221229181526.53766-5-samuel@sholland.org>
References: <20221229181526.53766-1-samuel@sholland.org>
        <20221229181526.53766-5-samuel@sholland.org>
Organization: Bootlin
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: quoted-printable
Precedence: bulk

Hi Samuel,

samuel@sholland.org wrote on Thu, 29 Dec 2022 12:15:23 -0600:

> This is already accounted for in the subtraction for OOB, since the BBM
> overlaps the first OOB dword. With this change, the driver picks the
> same ECC strength as the vendor driver.
>=20
> Fixes: 4796d8655915 ("mtd: nand: sunxi: Support ECC maximization")
> Signed-off-by: Samuel Holland <samuel@sholland.org>
> ---
>=20
>  drivers/mtd/nand/raw/sunxi_nand.c | 3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
>=20
> diff --git a/drivers/mtd/nand/raw/sunxi_nand.c b/drivers/mtd/nand/raw/sun=
xi_nand.c
> index 1bddeb1be66f..1ecf2cee343b 100644
> --- a/drivers/mtd/nand/raw/sunxi_nand.c
> +++ b/drivers/mtd/nand/raw/sunxi_nand.c
> @@ -1643,8 +1643,7 @@ static int sunxi_nand_hw_ecc_ctrl_init(struct nand_=
chip *nand,
>  		ecc->size =3D 1024;
>  		nsectors =3D mtd->writesize / ecc->size;
> =20
> -		/* Reserve 2 bytes for the BBM */
> -		bytes =3D (mtd->oobsize - 2) / nsectors;
> +		bytes =3D mtd->oobsize / nsectors;

I'm sorry but I don't think we can make this work. This change would
break all existing users...

> =20
>  		/* 4 non-ECC bytes are added before each ECC bytes section */
>  		bytes -=3D 4;


Thanks,
Miqu=C3=A8l