linux-kernel - Re: [PATCH v3 2/2] mtd: rawnand: brcmnand: improve hamming oob layout

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Date:   Tue, 12 May 2020 09:08:44 +0200
From:   Miquel Raynal <miquel.raynal@...tlin.com>
To:     Álvaro Fernández Rojas <noltari@...il.com>
Cc:     computersforpeace@...il.com, kdasu.kdev@...il.com, richard@....at,
        vigneshr@...com, sumit.semwal@...aro.org,
        linux-mtd@...ts.infradead.org,
        bcm-kernel-feedback-list@...adcom.com,
        linux-kernel@...r.kernel.org, linux-media@...r.kernel.org,
        dri-devel@...ts.freedesktop.org, linaro-mm-sig@...ts.linaro.org
Subject: Re: [PATCH v3 2/2] mtd: rawnand: brcmnand: improve hamming oob
 layout

Hi Álvaro,

Álvaro Fernández Rojas <noltari@...il.com> wrote on Tue, 12 May 2020
08:00:23 +0200:

> The current code generates 8 oob sections:
> S1	1-5
> ECC	6-8
> S2	9-15
> S3	16-21
> ECC	22-24
> S4	25-31
> S5	32-37
> ECC	38-40
> S6	41-47
> S7	48-53
> ECC	54-56
> S8	57-63
> 
> Change it by merging continuous sections:
> S1	1-5
> ECC	6-8
> S2	9-21
> ECC	22-24
> S3	25-37
> ECC	38-40
> S4	41-53
> ECC	54-56
> S5	57-63
> 
> Fixes: ef5eeea6e911 ("mtd: nand: brcm: switch to mtd_ooblayout_ops")

Sorry for leading you the wrong way, actually this patch does not
deserve a Fixes tag.

> Signed-off-by: Álvaro Fernández Rojas <noltari@...il.com>
> ---
>  v3: invert patch order
>  v2: keep original comment and fix correctly skip byte 6 for small-page nand
> 
>  drivers/mtd/nand/raw/brcmnand/brcmnand.c | 37 ++++++++++++------------
>  1 file changed, 18 insertions(+), 19 deletions(-)
> 
> diff --git a/drivers/mtd/nand/raw/brcmnand/brcmnand.c b/drivers/mtd/nand/raw/brcmnand/brcmnand.c
> index 1c1070111ebc..0a1d76fde37b 100644
> --- a/drivers/mtd/nand/raw/brcmnand/brcmnand.c
> +++ b/drivers/mtd/nand/raw/brcmnand/brcmnand.c
> @@ -1100,33 +1100,32 @@ static int brcmnand_hamming_ooblayout_free(struct mtd_info *mtd, int section,
>  	struct brcmnand_cfg *cfg = &host->hwcfg;
>  	int sas = cfg->spare_area_size << cfg->sector_size_1k;
>  	int sectors = cfg->page_size / (512 << cfg->sector_size_1k);
> +	u32 next;
>  
> -	if (section >= sectors * 2)
> +	if (section > sectors)
>  		return -ERANGE;
>  
> -	oobregion->offset = (section / 2) * sas;
> +	next = (section * sas);
> +	if (section < sectors)
> +		next += 6;
>  
> -	if (section & 1) {
> -		oobregion->offset += 9;
> -		oobregion->length = 7;
> +	if (section) {
> +		oobregion->offset = ((section - 1) * sas) + 9;
>  	} else {
> -		oobregion->length = 6;
> -
> -		/* First sector of each page may have BBI */
> -		if (!section) {
> -			/*
> -			 * Small-page NAND use byte 6 for BBI while large-page
> -			 * NAND use bytes 0 and 1.
> -			 */
> -			if (cfg->page_size > 512) {
> -				oobregion->offset += 2;
> -				oobregion->length -= 2;
> -			} else {
> -				oobregion->length--;
> -			}
> +		/*
> +		 * Small-page NAND use byte 6 for BBI while large-page
> +		 * NAND use bytes 0 and 1.
> +		 */
> +		if (cfg->page_size > 512) {
> +			oobregion->offset = 2;
> +		} else {
> +			oobregion->offset = 0;
> +			next--;

This next-- seems very strange, can you explain?

>  		}
>  	}
>  
> +	oobregion->length = next - oobregion->offset;
> +
>  	return 0;
>  }
>  


Thanks,
Miquèl