linux-kernel - Re: [PATCH 3/4] mtd: nand: mxc

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Date: Mon, 6 May 2024 16:05:08 +0200
From: Miquel Raynal <miquel.raynal@...tlin.com>
To: Sascha Hauer <s.hauer@...gutronix.de>
Cc: Richard Weinberger <richard@....at>, Vignesh Raghavendra
 <vigneshr@...com>, linux-mtd@...ts.infradead.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/4] mtd: nand: mxc_nand: support software ECC

Hi Sascha,

s.hauer@...gutronix.de wrote on Wed, 17 Apr 2024 09:13:30 +0200:

> To support software ECC we still need the driver provided read_oob,
> read_page_raw and write_page_raw ops, so set them unconditionally
> no matter which engine_type we use. The OOB layout on the other hand
> represents the layout the i.MX ECC hardware uses, so set this only
> when NAND_ECC_ENGINE_TYPE_ON_HOST is in use.
> 
> With these changes the driver can be used with software BCH ECC which
> is useful for NAND chips that require a stronger ECC than the i.MX
> hardware supports.
> 
> Signed-off-by: Sascha Hauer <s.hauer@...gutronix.de>
> ---
>  drivers/mtd/nand/raw/mxc_nand.c | 9 +++++----
>  1 file changed, 5 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/mtd/nand/raw/mxc_nand.c b/drivers/mtd/nand/raw/mxc_nand.c
> index fc70c65dea268..f44c130dca18d 100644
> --- a/drivers/mtd/nand/raw/mxc_nand.c
> +++ b/drivers/mtd/nand/raw/mxc_nand.c
> @@ -1394,15 +1394,16 @@ static int mxcnd_attach_chip(struct nand_chip *chip)
>  	chip->ecc.bytes = host->devtype_data->eccbytes;
>  	host->eccsize = host->devtype_data->eccsize;
>  	chip->ecc.size = 512;
> -	mtd_set_ooblayout(mtd, host->devtype_data->ooblayout);
> +
> +	chip->ecc.read_oob = mxc_nand_read_oob;
> +	chip->ecc.read_page_raw = mxc_nand_read_page_raw;
> +	chip->ecc.write_page_raw = mxc_nand_write_page_raw;
>  
>  	switch (chip->ecc.engine_type) {
>  	case NAND_ECC_ENGINE_TYPE_ON_HOST:
> +		mtd_set_ooblayout(mtd, host->devtype_data->ooblayout);
>  		chip->ecc.read_page = mxc_nand_read_page;
> -		chip->ecc.read_page_raw = mxc_nand_read_page_raw;
> -		chip->ecc.read_oob = mxc_nand_read_oob;
>  		chip->ecc.write_page = mxc_nand_write_page_ecc;
> -		chip->ecc.write_page_raw = mxc_nand_write_page_raw;
>  		chip->ecc.write_oob = mxc_nand_write_oob;
>  		break;

You also need to disable the ECC engine by default (and then you're
free to use the raw page helpers).

I thought patch 4 was needed for this patch to work, do you confirm?
Otherwise with the little change requested I might also merge this one.

Thanks, Miquèl