[PATCH 2/2] mtd: rawnand: Bypass a couple of sanity checks during NAND identification

[Sascha Hauer]

Hi Miquel,

On Tue, May 07, 2024 at 06:05:46PM +0200, Miquel Raynal wrote:
> Early during NAND identification, mtd_info fields have not yet been
> initialized (namely, writesize and oobsize) and thus cannot be used for
> sanity checks yet. Of course if there is a misuse of
> nand_change_read_column_op() so early we won't be warned, but there is
> anyway no actual check to perform at this stage as we do not yet know
> the NAND geometry.
> 
> So, if the fields are empty, especially mtd->writesize which is *always*
> set quite rapidly after identification, let's skip the sanity checks.
> 
> nand_change_read_column_op() is subject to be used early for ONFI/JEDEC
> identification in the very unlikely case of:
> - bitflips appearing in the parameter page,
> - the controller driver not supporting simple DATA_IN cycles.
> 
> Fixes: c27842e7e11f ("mtd: rawnand: onfi: Adapt the parameter page read to constraint controllers")
> Fixes: daca31765e8b ("mtd: rawnand: jedec: Adapt the parameter page read to constraint controllers")
> Cc: stable at vger.kernel.org
> Reported-by: Alexander Dahl <ada at thorsis.com>
> Closes: https://lore.kernel.org/linux-mtd/20240306-shaky-bunion-d28b65ea97d7@thorsis.com/
> Reported-by: Steven Seeger <steven.seeger at flightsystems.net>
> Closes: https://lore.kernel.org/linux-mtd/DM6PR05MB4506554457CF95191A670BDEF7062@DM6PR05MB4506.namprd05.prod.outlook.com/
> Signed-off-by: Miquel Raynal <miquel.raynal at bootlin.com>
> ---
>  drivers/mtd/nand/raw/nand_base.c | 12 +++++++-----
>  1 file changed, 7 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/mtd/nand/raw/nand_base.c b/drivers/mtd/nand/raw/nand_base.c
> index 248e654ecefd..a66e73cd68cb 100644
> --- a/drivers/mtd/nand/raw/nand_base.c
> +++ b/drivers/mtd/nand/raw/nand_base.c
> @@ -1440,12 +1440,14 @@ int nand_change_read_column_op(struct nand_chip *chip,
>  	if (len && !buf)
>  		return -EINVAL;
>  
> -	if (offset_in_page + len > mtd->writesize + mtd->oobsize)
> -		return -EINVAL;
> +	if (mtd->writesize) {
> +		if ((offset_in_page + len > mtd->writesize + mtd->oobsize))
> +			return -EINVAL;
>  
> -	/* Small page NANDs do not support column change. */
> -	if (mtd->writesize <= 512)
> -		return -ENOTSUPP;
> +		/* Small page NANDs do not support column change. */
> +		if (mtd->writesize <= 512)
> +			return -ENOTSUPP;
> +	}

This is not enough. A few lines further down nand_fill_column_cycles()
is called which also uses mtd->writesize. This function also needs to
know if we have a large page or small page NAND, so bypassing the checks
won't be enough there.

Sascha

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