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

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Message-Id: <5377BB9D-35EB-4531-8E03-A7483D3134E4@gmail.com>
Date:   Tue, 12 May 2020 09:12:10 +0200
From:   Álvaro Fernández Rojas <noltari@...il.com>
To:     Miquel Raynal <miquel.raynal@...tlin.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 Miquel,

I also had a hard time understanding your email.
It was quite misleading.

> El 12 may 2020, a las 9:08, Miquel Raynal <miquel.raynal@...tlin.com> escribió:
> 
> 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.

Do I need to resend this again?
Looks like no matter what I do it’s always wrong...

> 
>> 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?

In this case next will be 6 (which is the first ECC byte).
However, for small page NANDs byte 5 is reserved for BBT, so we want next to be 5 only in this case.

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

Regards,
Álvaro.