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Date:   Fri, 15 Oct 2021 09:38:31 +0100
From:   Paul Cercueil <paul@...pouillou.net>
To:     Miquel Raynal <miquel.raynal@...tlin.com>
Cc:     Richard Weinberger <richard@....at>,
        Vignesh Raghavendra <vigneshr@...com>,
        Harvey Hunt <harveyhuntnexus@...il.com>, list@...ndingux.net,
        linux-mtd@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-mips@...r.kernel.org, stable@...r.kernel.org
Subject: Re: [PATCH 2/3] mtd: rawnand: Export nand_read_page_hwecc_oob_first()

Hi Miquel,

Le ven., oct. 15 2021 at 08:13:13 +0200, Miquel Raynal 
<miquel.raynal@...tlin.com> a écrit :
> Hi Paul,
> 
> paul@...pouillou.net wrote on Sat,  9 Oct 2021 20:49:51 +0200:
> 
>>  Move the function nand_read_page_hwecc_oob_first() (previously
>>  nand_davinci_read_page_hwecc_oob_first()) to nand_base.c, and 
>> export it
>>  as a GPL symbol, so that it can be used by more modules.
>> 
>>  Cc: <stable@...r.kernel.org> # v5.2
>>  Fixes: a0ac778eb82c ("mtd: rawnand: ingenic: Add support for the 
>> JZ4740")
>>  Signed-off-by: Paul Cercueil <paul@...pouillou.net>
>>  ---
>>   drivers/mtd/nand/raw/davinci_nand.c | 70 
>> +----------------------------
>>   drivers/mtd/nand/raw/nand_base.c    | 69 
>> ++++++++++++++++++++++++++++
>>   include/linux/mtd/rawnand.h         |  2 +
>>   3 files changed, 72 insertions(+), 69 deletions(-)
>> 
>>  diff --git a/drivers/mtd/nand/raw/davinci_nand.c 
>> b/drivers/mtd/nand/raw/davinci_nand.c
>>  index 89de24d3bb7a..45fec8c192ab 100644
>>  --- a/drivers/mtd/nand/raw/davinci_nand.c
>>  +++ b/drivers/mtd/nand/raw/davinci_nand.c
>>  @@ -371,74 +371,6 @@ static int nand_davinci_correct_4bit(struct 
>> nand_chip *chip, u_char *data,
>>   	return corrected;
>>   }
>> 
>>  -/**
>>  - * nand_read_page_hwecc_oob_first - hw ecc, read oob first
>>  - * @chip: nand chip info structure
>>  - * @buf: buffer to store read data
>>  - * @oob_required: caller requires OOB data read to chip->oob_poi
>>  - * @page: page number to read
>>  - *
>>  - * Hardware ECC for large page chips, require OOB to be read 
>> first. For this
>>  - * ECC mode, the write_page method is re-used from ECC_HW. These 
>> methods
>>  - * read/write ECC from the OOB area, unlike the ECC_HW_SYNDROME 
>> support with
>>  - * multiple ECC steps, follows the "infix ECC" scheme and 
>> reads/writes ECC from
>>  - * the data area, by overwriting the NAND manufacturer bad block 
>> markings.
>>  - */
>>  -static int nand_davinci_read_page_hwecc_oob_first(struct nand_chip 
>> *chip,
>>  -						  uint8_t *buf,
>>  -						  int oob_required, int page)
>>  -{
>>  -	struct mtd_info *mtd = nand_to_mtd(chip);
>>  -	int i, eccsize = chip->ecc.size, ret;
>>  -	int eccbytes = chip->ecc.bytes;
>>  -	int eccsteps = chip->ecc.steps;
>>  -	uint8_t *p = buf;
>>  -	uint8_t *ecc_code = chip->ecc.code_buf;
>>  -	unsigned int max_bitflips = 0;
>>  -
>>  -	/* Read the OOB area first */
>>  -	ret = nand_read_oob_op(chip, page, 0, chip->oob_poi, 
>> mtd->oobsize);
>>  -	if (ret)
>>  -		return ret;
>>  -
>>  -	ret = nand_read_page_op(chip, page, 0, NULL, 0);
>>  -	if (ret)
>>  -		return ret;
>>  -
>>  -	ret = mtd_ooblayout_get_eccbytes(mtd, ecc_code, chip->oob_poi, 0,
>>  -					 chip->ecc.total);
>>  -	if (ret)
>>  -		return ret;
>>  -
>>  -	for (i = 0; eccsteps; eccsteps--, i += eccbytes, p += eccsize) {
>>  -		int stat;
>>  -
>>  -		chip->ecc.hwctl(chip, NAND_ECC_READ);
>>  -
>>  -		ret = nand_read_data_op(chip, p, eccsize, false, false);
>>  -		if (ret)
>>  -			return ret;
>>  -
>>  -		stat = chip->ecc.correct(chip, p, &ecc_code[i], NULL);
>>  -		if (stat == -EBADMSG &&
>>  -		    (chip->ecc.options & NAND_ECC_GENERIC_ERASED_CHECK)) {
>>  -			/* check for empty pages with bitflips */
>>  -			stat = nand_check_erased_ecc_chunk(p, eccsize,
>>  -							   &ecc_code[i],
>>  -							   eccbytes, NULL, 0,
>>  -							   chip->ecc.strength);
>>  -		}
>>  -
>>  -		if (stat < 0) {
>>  -			mtd->ecc_stats.failed++;
>>  -		} else {
>>  -			mtd->ecc_stats.corrected += stat;
>>  -			max_bitflips = max_t(unsigned int, max_bitflips, stat);
>>  -		}
>>  -	}
>>  -	return max_bitflips;
>>  -}
>>  -
>>   
>> /*----------------------------------------------------------------------*/
>> 
>>   /* An ECC layout for using 4-bit ECC with small-page flash, storing
>>  @@ -648,7 +580,7 @@ static int davinci_nand_attach_chip(struct 
>> nand_chip *chip)
>>   			} else if (chunks == 4 || chunks == 8) {
>>   				mtd_set_ooblayout(mtd,
>>   						  nand_get_large_page_ooblayout());
>>  -				chip->ecc.read_page = nand_davinci_read_page_hwecc_oob_first;
>>  +				chip->ecc.read_page = nand_read_page_hwecc_oob_first;
>>   			} else {
>>   				return -EIO;
>>   			}
>>  diff --git a/drivers/mtd/nand/raw/nand_base.c 
>> b/drivers/mtd/nand/raw/nand_base.c
>>  index 3d6c6e880520..cb5f343b9fa2 100644
>>  --- a/drivers/mtd/nand/raw/nand_base.c
>>  +++ b/drivers/mtd/nand/raw/nand_base.c
>>  @@ -3160,6 +3160,75 @@ static int nand_read_page_hwecc(struct 
>> nand_chip *chip, uint8_t *buf,
>>   	return max_bitflips;
>>   }
>> 
>>  +/**
>>  + * nand_read_page_hwecc_oob_first - Hardware ECC page read with ECC
>>  + *                                  data read from OOB area
>>  + * @chip: nand chip info structure
>>  + * @buf: buffer to store read data
>>  + * @oob_required: caller requires OOB data read to chip->oob_poi
>>  + * @page: page number to read
>>  + *
>>  + * Hardware ECC for large page chips, require OOB to be read 
>> first. For this
> 
> requires
> 
> With this ECC configuration?
> 
>>  + * ECC mode, the write_page method is re-used from ECC_HW. These 
>> methods
> 
> I do not understand this sentence nor the next one about syndrome. I
> believe it is related to your engine and should not leak into the 
> core.
> 
>>  + * read/write ECC from the OOB area, unlike the ECC_HW_SYNDROME 
>> support with
>>  + * multiple ECC steps, follows the "infix ECC" scheme and 
>> reads/writes ECC from
>>  + * the data area, by overwriting the NAND manufacturer bad block 
>> markings.
> 
> That's a sentence I don't like. What do you mean exactly?
> 
> What "Infix ECC" scheme is?
> 
> Do you mean that unlike the syndrome  mode it *does not* overwrite the
> BBM ?

I don't mean anything. I did not write that comment. I just moved the 
function verbatim with no changes. If something needs to be fixed, then 
it needs to be fixed before/after this patch.

>>  + */
>>  +int nand_read_page_hwecc_oob_first(struct nand_chip *chip, uint8_t 
>> *buf,
>>  +				   int oob_required, int page)
>>  +{
>>  +	struct mtd_info *mtd = nand_to_mtd(chip);
>>  +	int i, eccsize = chip->ecc.size, ret;
>>  +	int eccbytes = chip->ecc.bytes;
>>  +	int eccsteps = chip->ecc.steps;
>>  +	uint8_t *p = buf;
>>  +	uint8_t *ecc_code = chip->ecc.code_buf;
>>  +	unsigned int max_bitflips = 0;
>>  +
>>  +	/* Read the OOB area first */
>>  +	ret = nand_read_oob_op(chip, page, 0, chip->oob_poi, 
>> mtd->oobsize);
>>  +	if (ret)
>>  +		return ret;
>>  +
>>  +	ret = nand_read_page_op(chip, page, 0, NULL, 0);
> 
> Definitely not, your are requesting the chip to do the read_page
> operation twice. You only need a nand_change_read_column I believe.

Again, this code is just being moved around - don't shoot the messenger 
:)

>>  +	if (ret)
>>  +		return ret;
>>  +
>>  +	ret = mtd_ooblayout_get_eccbytes(mtd, ecc_code, chip->oob_poi, 0,
>>  +					 chip->ecc.total);
>>  +	if (ret)
>>  +		return ret;
>>  +
>>  +	for (i = 0; eccsteps; eccsteps--, i += eccbytes, p += eccsize) {
>>  +		int stat;
>>  +
>>  +		chip->ecc.hwctl(chip, NAND_ECC_READ);
>>  +
>>  +		ret = nand_read_data_op(chip, p, eccsize, false, false);
>>  +		if (ret)
>>  +			return ret;
>>  +
>>  +		stat = chip->ecc.correct(chip, p, &ecc_code[i], NULL);
>>  +		if (stat == -EBADMSG &&
>>  +		    (chip->ecc.options & NAND_ECC_GENERIC_ERASED_CHECK)) {
>>  +			/* check for empty pages with bitflips */
>>  +			stat = nand_check_erased_ecc_chunk(p, eccsize,
>>  +							   &ecc_code[i],
>>  +							   eccbytes, NULL, 0,
>>  +							   chip->ecc.strength);
>>  +		}
>>  +
>>  +		if (stat < 0) {
>>  +			mtd->ecc_stats.failed++;
>>  +		} else {
>>  +			mtd->ecc_stats.corrected += stat;
>>  +			max_bitflips = max_t(unsigned int, max_bitflips, stat);
>>  +		}
>>  +	}
>>  +	return max_bitflips;
>>  +}
>>  +EXPORT_SYMBOL_GPL(nand_read_page_hwecc_oob_first);
>>  +
>>   /**
>>    * nand_read_page_syndrome - [REPLACEABLE] hardware ECC syndrome 
>> based page read
>>    * @chip: nand chip info structure
>>  diff --git a/include/linux/mtd/rawnand.h 
>> b/include/linux/mtd/rawnand.h
>>  index b2f9dd3cbd69..5b88cd51fadb 100644
>>  --- a/include/linux/mtd/rawnand.h
>>  +++ b/include/linux/mtd/rawnand.h
>>  @@ -1539,6 +1539,8 @@ int nand_read_data_op(struct nand_chip *chip, 
>> void *buf, unsigned int len,
>>   		      bool force_8bit, bool check_only);
>>   int nand_write_data_op(struct nand_chip *chip, const void *buf,
>>   		       unsigned int len, bool force_8bit);
>>  +int nand_read_page_hwecc_oob_first(struct nand_chip *chip, uint8_t 
>> *buf,
>>  +				   int oob_required, int page);
> 
> You certainly want to add this symbol closer to the other read/write
> page helpers?

Where would that be? The other read/write page helpers are all "static" 
so they don't appear in any header.

Cheers,
-Paul

>> 
>>   /* Scan and identify a NAND device */
>>   int nand_scan_with_ids(struct nand_chip *chip, unsigned int 
>> max_chips,
> 
> 
> Thanks,
> Miquèl


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