linux-kernel - Re: [PATCH v1] mtd: rawnand: meson: handle OOB buffer according OOB layout

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Message-ID: <20231124100657.245d258f@xps-13>
Date:   Fri, 24 Nov 2023 10:06:57 +0100
From:   Miquel Raynal <miquel.raynal@...tlin.com>
To:     Arseniy Krasnov <avkrasnov@...utedevices.com>
Cc:     Viacheslav Bocharov <adeep@...ina.in>,
        Richard Weinberger <richard@....at>,
        Vignesh Raghavendra <vigneshr@...com>,
        Neil Armstrong <neil.armstrong@...aro.org>,
        Kevin Hilman <khilman@...libre.com>,
        Jerome Brunet <jbrunet@...libre.com>,
        Martin Blumenstingl <martin.blumenstingl@...glemail.com>,
        <oxffffaa@...il.com>, <kernel@...rdevices.ru>,
        <linux-mtd@...ts.infradead.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v1] mtd: rawnand: meson: handle OOB buffer according OOB
 layout

Hi Arseniy,

avkrasnov@...utedevices.com wrote on Fri, 24 Nov 2023 10:50:54 +0300:

> Hello all, 2 weeks from 9.11, please ping

I'm waiting for Viacheslav.

> 
> Thanks, Arseniy
> 
> 
> On 09.11.2023 12:09, Arseniy Krasnov wrote:
> > Hello, thanks for review!
> > 
> > On 09.11.2023 11:06, Viacheslav Bocharov wrote:  
> >> Hi!
> >>
> >> On Thu, 2023-11-09 at 08:39 +0300, Arseniy Krasnov wrote:  
> >>> In case of MTD_OPS_AUTO_OOB mode, MTD/NAND layer fills/reads OOB buffer
> >>> according current OOB layout so we need to follow it in the driver.
> >>>
> >>> Signed-off-by: Arseniy Krasnov <avkrasnov@...utedevices.com>
> >>> ---
> >>>  drivers/mtd/nand/raw/meson_nand.c | 4 ++--
> >>>  1 file changed, 2 insertions(+), 2 deletions(-)
> >>>
> >>> diff --git a/drivers/mtd/nand/raw/meson_nand.c b/drivers/mtd/nand/raw/meson_nand.c
> >>> index 561d46d860b7..0d4d358152d7 100644
> >>> --- a/drivers/mtd/nand/raw/meson_nand.c
> >>> +++ b/drivers/mtd/nand/raw/meson_nand.c
> >>> @@ -510,7 +510,7 @@ static void meson_nfc_set_user_byte(struct nand_chip *nand, u8 *oob_buf)
> >>>  	__le64 *info;
> >>>  	int i, count;
> >>>  
> >>> -	for (i = 0, count = 0; i < nand->ecc.steps; i++, count += 2) {
> >>> +	for (i = 0, count = 0; i < nand->ecc.steps; i++, count += (2 + nand->ecc.bytes)) {
> >>>  		info = &meson_chip->info_buf[i];
> >>>  		*info |= oob_buf[count];
> >>>  		*info |= oob_buf[count + 1] << 8;  
> >> Seems something wrong with your logic here.
> >> I think this code should most likely look like this:
> >>
> >> for (i = 0, count = 0; i < nand->ecc.steps; i++, count += nand->ecc.bytes) {
> >>     info = &meson_chip->info_buf[i];
> >>     *info |= oob_buf[count];
> >>     if (nand->ecc.bytes > 1)
> >>       *info |= oob_buf[count + 1] << 8;
> >> }  
> > 
> > For 64 bytes OOB and 512 bytes ECC this driver reports free areas as:
> > 
> > AA AA BB BB BB BB BB BB BB BB BB BB BB BB BB BB
> > AA AA BB BB BB BB BB BB BB BB BB BB BB BB BB BB
> > AA AA BB BB BB BB BB BB BB BB BB BB BB BB BB BB
> > AA AA BB BB BB BB BB BB BB BB BB BB BB BB BB BB
> > 
> > where AA is free byte(user byte), BB - ECC codes. So to access user bytes
> > we need bytes 0,1,16,17,32,33,48,49. nand->ecc.bytes == 14, so 'count' is
> > increased at 16 every iteration, so i guess this is correct.
> > 
> > WDYT?
> > 
> > Thanks, Arseniy
> >   
> >>
> >>  
> >>> @@ -523,7 +523,7 @@ static void meson_nfc_get_user_byte(struct nand_chip *nand, u8 *oob_buf)
> >>>  	__le64 *info;
> >>>  	int i, count;
> >>>  
> >>> -	for (i = 0, count = 0; i < nand->ecc.steps; i++, count += 2) {
> >>> +	for (i = 0, count = 0; i < nand->ecc.steps; i++, count += (2 + nand->ecc.bytes)) {
> >>>  		info = &meson_chip->info_buf[i];
> >>>  		oob_buf[count] = *info;
> >>>  		oob_buf[count + 1] = *info >> 8;  
> >> And there:
> >>
> >> for (i = 0, count = 0; i < nand->ecc.steps; i++, count += nand->ecc.bytes) {
> >>     info = &meson_chip->info_buf[i];
> >>     oob_buf[count] = *info;
> >>     if (nand->ecc.bytes > 1)
> >>         oob_buf[count + 1] = *info >> 8;
> >> }
> >>
> >>
> >> This is more similar to the behavior of similar functions in the proprietary U-Boot.
> >>
> >> --
> >> Viacheslav Bocharov
> >>  


Thanks,
Miquèl