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

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Date:   Tue, 12 May 2020 09:19:58 +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
09:12:10 +0200:

> 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...

Please don't give up! It is normal to work back and forth with the
community. I need the patch to be clear and bug-free so I ask you to
make changes and ask questions, that's how it works. But all your
patches are enhancing this driver so please keep posting!

> 
> >   
> >> 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.

That's clear, please add a comment there then.

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



Thanks,
Miquèl