Re: [PATCH 3/6] mtd: rawnand: sunxi: do not count BBM bytes twice

["Jernej Škrabec" <jernej.skrabec@gmail.com>]

Dne petek, 20. februar 2026 ob 17:10:08 Srednjeevropski standardni čas je Richard Genoud napisal(a):
> BBM is part of USER_DATA section, so we should remove it twice
> 
> This was working ok because we are on the safe size, advertising that
> there was 2 bytes less available than reality.

Missing "in" before "reality".

> 
> But we can't change old platforms, since it may lead to a different ECC
> strength, so, introduce a legacy flag for old platforms, and switch the
> new platforms to the correct count.

There aren't any users of H6/H616 driver, right? If it would be, ECC strength
can't be changed, since it can impact systems, which already use it.

Best regards,
Jernej

> 
> Signed-off-by: Richard Genoud <richard.genoud@bootlin.com>
> ---
>  drivers/mtd/nand/raw/sunxi_nand.c | 23 ++++++++++++++++++++---
>  1 file changed, 20 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/mtd/nand/raw/sunxi_nand.c b/drivers/mtd/nand/raw/sunxi_nand.c
> index 9c6e0625e34f..99d305bbda53 100644
> --- a/drivers/mtd/nand/raw/sunxi_nand.c
> +++ b/drivers/mtd/nand/raw/sunxi_nand.c
> @@ -281,6 +281,8 @@ static inline struct sunxi_nand_chip *to_sunxi_nand(struct nand_chip *nand)
>   * @has_ecc_block_512:	If the ECC can handle 512B or only 1024B chuncks
>   * @has_ecc_clk:	If the controller needs an ECC clock.
>   * @has_mbus_clk:	If the controller needs a mbus clock.
> + * @legacy_max_strength:If the maximize strength function was off by 2 bytes
> + *			NB: this should not be used in new controllers
>   * @reg_io_data:	I/O data register
>   * @reg_ecc_err_cnt:	ECC error counter register
>   * @reg_user_data:	User data register
> @@ -310,6 +312,7 @@ struct sunxi_nfc_caps {
>  	bool has_ecc_block_512;
>  	bool has_ecc_clk;
>  	bool has_mbus_clk;
> +	bool legacy_max_strength;
>  	unsigned int reg_io_data;
>  	unsigned int reg_ecc_err_cnt;
>  	unsigned int reg_user_data;
> @@ -1811,10 +1814,22 @@ static int sunxi_nand_hw_ecc_ctrl_init(struct nand_chip *nand,
>  		ecc->size = 1024;
>  		nsectors = mtd->writesize / ecc->size;
>  
> -		/* Reserve 2 bytes for the BBM */
> -		bytes = (mtd->oobsize - 2) / nsectors;
> +		/*
> +		 * The 2 BBM bytes should not be removed from the grand total,
> +		 * because they are part of the USER_DATA_SZ.
> +		 * But we can't modify that for older platform since it may
> +		 * result in a stronger ECC at the end, and break the
> +		 * compatibility.
> +		 */
> +		if (nfc->caps->legacy_max_strength)
> +			bytes = (mtd->oobsize - 2) / nsectors;
> +		else
> +			bytes = mtd->oobsize / nsectors;
>  
> -		/* 4 non-ECC bytes are added before each ECC bytes section */
> +		/*
> +		 * USER_DATA_SZ non-ECC bytes are added before each ECC bytes
> +		 * section, they contain the 2 BBM bytes
> +		 */
>  		bytes -= USER_DATA_SZ;
>  
>  		/* and bytes has to be even. */
> @@ -2379,6 +2394,7 @@ static const u8 sunxi_user_data_len_h6[] = {
>  
>  static const struct sunxi_nfc_caps sunxi_nfc_a10_caps = {
>  	.has_ecc_block_512 = true,
> +	.legacy_max_strength = true,
>  	.reg_io_data = NFC_REG_A10_IO_DATA,
>  	.reg_ecc_err_cnt = NFC_REG_A10_ECC_ERR_CNT,
>  	.reg_user_data = NFC_REG_A10_USER_DATA,
> @@ -2400,6 +2416,7 @@ static const struct sunxi_nfc_caps sunxi_nfc_a10_caps = {
>  static const struct sunxi_nfc_caps sunxi_nfc_a23_caps = {
>  	.has_mdma = true,
>  	.has_ecc_block_512 = true,
> +	.legacy_max_strength = true,
>  	.reg_io_data = NFC_REG_A23_IO_DATA,
>  	.reg_ecc_err_cnt = NFC_REG_A10_ECC_ERR_CNT,
>  	.reg_user_data = NFC_REG_A10_USER_DATA,
>