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

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Message-ID: <ab3f6734-357c-9937-2e21-a935850d3af8@salutedevices.com>
Date:   Fri, 24 Nov 2023 10:50:54 +0300
From:   Arseniy Krasnov <avkrasnov@...utedevices.com>
To:     Viacheslav Bocharov <adeep@...ina.in>,
        Miquel Raynal <miquel.raynal@...tlin.com>,
        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>
CC:     <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

Hello all, 2 weeks from 9.11, please ping

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
>>