linux-kernel - Re: [PATCH v4 3/5] mtd: rawnand: meson: always read whole OOB bytes

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Message-ID: <84a2e0c4-cc6f-1743-ee93-c13bc8bf09f1@sberdevices.ru>
Date:   Tue, 23 May 2023 20:27:35 +0300
From:   Arseniy Krasnov <avkrasnov@...rdevices.ru>
To:     Miquel Raynal <miquel.raynal@...tlin.com>
CC:     Liang Yang <liang.yang@...ogic.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>,
        Jianxin Pan <jianxin.pan@...ogic.com>,
        Yixun Lan <yixun.lan@...ogic.com>, <oxffffaa@...il.com>,
        <kernel@...rdevices.ru>, <linux-mtd@...ts.infradead.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-amlogic@...ts.infradead.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v4 3/5] mtd: rawnand: meson: always read whole OOB bytes



On 22.05.2023 18:38, Miquel Raynal wrote:
> Hi Arseniy,
> 
> AVKrasnov@...rdevices.ru wrote on Mon, 15 May 2023 12:44:37 +0300:
> 
>> This changes size of read access to OOB area by reading all bytes of
>> OOB (free bytes + ECC engine bytes).
> 
> This is normally up to the user (user in your case == jffs2). The
> controller driver should expose a number of user accessible bytes and
> then when users want the OOB area, they should access it entirely. On
> top of that read, they can extract (or "write only") the user bytes.

Sorry, I didn't get it. If driver exposes N bytes of user accessible bytes,
I must always return whole OOB yes? E.g. N + rest of OOB

> 
>> Signed-off-by: Arseniy Krasnov <AVKrasnov@...rdevices.ru>
>> ---
>>  drivers/mtd/nand/raw/meson_nand.c | 24 ++++++++++++++++++++++++
>>  1 file changed, 24 insertions(+)
>>
>> diff --git a/drivers/mtd/nand/raw/meson_nand.c b/drivers/mtd/nand/raw/meson_nand.c
>> index 8526a6b87720..a31106c943d7 100644
>> --- a/drivers/mtd/nand/raw/meson_nand.c
>> +++ b/drivers/mtd/nand/raw/meson_nand.c
>> @@ -755,6 +755,30 @@ static int __meson_nfc_read_oob(struct nand_chip *nand, int page,
>>  	u32 oob_bytes;
>>  	u32 page_size;
>>  	int ret;
>> +	int i;
>> +
>> +	/* Read ECC codes and user bytes. */
>> +	for (i = 0; i < nand->ecc.steps; i++) {
>> +		u32 ecc_offs = nand->ecc.size * (i + 1) +
>> +			       NFC_OOB_PER_ECC(nand) * i;
>> +
>> +		ret = nand_read_page_op(nand, page, 0, NULL, 0);
>> +		if (ret)
>> +			return ret;
>> +
>> +		/* Use temporary buffer, because 'nand_change_read_column_op()'
>> +		 * seems work with some alignment, so we can't read data to
>> +		 * 'oob_buf' directly.
> 
> DMA?

Yes I guess, this address passed to exec_op code and used as DMA.

> 
>> +		 */
>> +		ret = nand_change_read_column_op(nand, ecc_offs, meson_chip->oob_buf,
>> +						 NFC_OOB_PER_ECC(nand), false);
>> +		if (ret)
>> +			return ret;
>> +
>> +		memcpy(oob_buf + i * NFC_OOB_PER_ECC(nand),
>> +		       meson_chip->oob_buf,
>> +		       NFC_OOB_PER_ECC(nand));
>> +	}
>>  
>>  	oob_bytes = meson_nfc_get_oob_bytes(nand);
>>  
> 
> 
> Thanks,
> Miquèl

Thanks, Arseniy