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

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Message-ID: <608cf897-55b3-4ccd-b99f-2ebba8bbf17f@lexina.in>
Date:   Fri, 24 Nov 2023 13:14:38 +0300
From:   Viacheslav <adeep@...ina.in>
To:     Miquel Raynal <miquel.raynal@...tlin.com>,
        Arseniy Krasnov <avkrasnov@...utedevices.com>
Cc:     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, Miquel!

24/11/2023 12.06, Miquel Raynal wrote:
> 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.

We discussed this update with Arseniy. My suggestion was based on the 
difference in patch from the algorithms used in amlogic u-boot.  Arseniy 
claims that everything works for them.

Unfortunately, I don't have the devices available to test this.

> 
>>
>> 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

--
Viacheslav Bocharov