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Date:   Fri, 12 Jun 2020 14:47:37 -0400
From:   Kamal Dasu <kdasu.kdev@...il.com>
To:     Álvaro Fernández Rojas <noltari@...il.com>
Cc:     Brian Norris <computersforpeace@...il.com>,
        Miquel Raynal <miquel.raynal@...tlin.com>,
        Richard Weinberger <richard@....at>,
        "R, Vignesh" <vigneshr@...com>,
        Sumit Semwal <sumit.semwal@...aro.org>,
        MTD Maling List <linux-mtd@...ts.infradead.org>,
        bcm-kernel-feedback-list <bcm-kernel-feedback-list@...adcom.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-media@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        linaro-mm-sig@...ts.linaro.org
Subject: Re: [PATCH] mtd: rawnand: brcmnand: force raw OOB writes

On Fri, Jun 5, 2020 at 1:07 PM Álvaro Fernández Rojas <noltari@...il.com> wrote:
>
> MTD_OPS_AUTO_OOB is writting OOB with ECC enabled, which changes all ECC bytes
> from an erased page to 0x00 when JFFS2 cleanmarkers are added with mtd-utils.
>          | BBI |   JFFS2   |   ECC   |   JFFS2   | Spare  |
> 00000800  ff ff 19 85 20 03 00 00  00 00 00 00 08 ff ff ff
>
> However, if OOB is written with ECC disabled, the JFFS2 cleanmarkers are
> correctly written without changing the ECC bytes:
>          | BBI |   JFFS2   |   ECC   |   JFFS2   | Spare  |
> 00000800  ff ff 19 85 20 03 ff ff  ff 00 00 00 08 ff ff ff

Both brcmand_write_oob_raw() and brcmnand_write_oob() use
brcmnand_write() that uses PROGRAM_PAGE cmd, means also programs data
areas and ECC when enabled  is always calculated on DATA+OOB.  since
in both cases we only want to modify OOB, data is always assumed to be
0xffs (means erased state). So as far as this api always is used on
the erased page it should be good. Are the sub-pages/oob areas read by
jffs2  also read without ecc enabled?. Just want to be sure that it
does not break any other utilities like nandwrite.

>
> Signed-off-by: Álvaro Fernández Rojas <noltari@...il.com>
> ---
>  drivers/mtd/nand/raw/brcmnand/brcmnand.c | 9 +--------
>  1 file changed, 1 insertion(+), 8 deletions(-)
>
> diff --git a/drivers/mtd/nand/raw/brcmnand/brcmnand.c b/drivers/mtd/nand/raw/brcmnand/brcmnand.c
> index 8f9ffb46a09f..566281770841 100644
> --- a/drivers/mtd/nand/raw/brcmnand/brcmnand.c
> +++ b/drivers/mtd/nand/raw/brcmnand/brcmnand.c
> @@ -2279,13 +2279,6 @@ static int brcmnand_write_page_raw(struct nand_chip *chip, const uint8_t *buf,
>         return nand_prog_page_end_op(chip);
>  }
>
> -static int brcmnand_write_oob(struct nand_chip *chip, int page)
> -{
> -       return brcmnand_write(nand_to_mtd(chip), chip,
> -                             (u64)page << chip->page_shift, NULL,
> -                             chip->oob_poi);
> -}
> -
>  static int brcmnand_write_oob_raw(struct nand_chip *chip, int page)
>  {
>         struct mtd_info *mtd = nand_to_mtd(chip);
> @@ -2642,7 +2635,7 @@ static int brcmnand_init_cs(struct brcmnand_host *host, struct device_node *dn)
>         chip->ecc.write_oob_raw = brcmnand_write_oob_raw;
>         chip->ecc.read_oob_raw = brcmnand_read_oob_raw;
>         chip->ecc.read_oob = brcmnand_read_oob;
> -       chip->ecc.write_oob = brcmnand_write_oob;
> +       chip->ecc.write_oob = brcmnand_write_oob_raw;
>
>         chip->controller = &ctrl->controller;
>
> --
> 2.26.2
>

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