linux-kernel - Re: [PATCH 3/4] drivers: mtd: spi-nand: repeat reading in regular mode if continuous reading fails

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Message-ID: <e01d40c2-cf1d-42f3-8589-da998b23901f@iopsys.eu>
Date: Mon, 18 Aug 2025 15:05:11 +0300
From: Mikhail Kshevetskiy <mikhail.kshevetskiy@...sys.eu>
To: Miquel Raynal <miquel.raynal@...tlin.com>
Cc: Richard Weinberger <richard@....at>, Vignesh Raghavendra
 <vigneshr@...com>, Lorenzo Bianconi <lorenzo@...nel.org>,
 Ray Liu <ray.liu@...oha.com>, Mark Brown <broonie@...nel.org>,
 Tudor Ambarus <tudor.ambarus@...aro.org>,
 Martin Kurbanov <mmkurbanov@...utedevices.com>,
 Takahiro Kuwano <Takahiro.Kuwano@...ineon.com>,
 Cheng Ming Lin <chengminglin@...c.com.tw>, linux-mtd@...ts.infradead.org,
 linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
 linux-spi@...r.kernel.org
Subject: Re: [PATCH 3/4] drivers: mtd: spi-nand: repeat reading in regular
 mode if continuous reading fails

Hello Miquèl, is there any comments to my v2 series? Mikhail

On 05.08.2025 18:36, Miquel Raynal wrote:
> On 04/08/2025 at 22:21:31 +03, Mikhail Kshevetskiy <mikhail.kshevetskiy@...sys.eu> wrote:
>
>> Continuous reading may result in multiple flash pages reading in one
>> operation. Unfortunately, not all spi-nand controllers support such
>> large reading. They will read less data. Unfortunately, the operation
>> can't be continued.
>>
>> In this case:
>>  * disable continuous reading on this (not good enough) spi controller
>>  * repeat reading in regular mode.
>>
>> Signed-off-by: Mikhail Kshevetskiy <mikhail.kshevetskiy@...sys.eu>
>> ---
>>  drivers/mtd/nand/spi/core.c | 19 +++++++++++++++----
>>  1 file changed, 15 insertions(+), 4 deletions(-)
>>
>> diff --git a/drivers/mtd/nand/spi/core.c b/drivers/mtd/nand/spi/core.c
>> index ff6a1e2fcfdc..88e4c00cccc4 100644
>> --- a/drivers/mtd/nand/spi/core.c
>> +++ b/drivers/mtd/nand/spi/core.c
>> @@ -431,7 +431,7 @@ static int spinand_read_from_cache_op(struct spinand_device *spinand,
>>  		 * Toggling the CS during a continuous read is forbidden.
>>  		 */
>>  		if (nbytes && req->continuous)
>> -			return -EIO;
>> +			return -E2BIG;
>>  	}
>>  
>>  	if (req->datalen)
>> @@ -893,15 +893,26 @@ static int spinand_mtd_read(struct mtd_info *mtd, loff_t from,
>>  	struct spinand_device *spinand = mtd_to_spinand(mtd);
>>  	struct mtd_ecc_stats old_stats;
>>  	unsigned int max_bitflips = 0;
>> -	int ret;
>> +	int ret = -E2BIG;
>>  
>>  	mutex_lock(&spinand->lock);
>>  
>>  	old_stats = mtd->ecc_stats;
>>  
>> -	if (spinand_use_cont_read(mtd, from, ops))
>> +	if (spinand_use_cont_read(mtd, from, ops)) {
>>  		ret = spinand_mtd_continuous_page_read(mtd, from, ops, &max_bitflips);
>> -	else
>> +		if (ret == -E2BIG) {
>> +			/*
>> +			 * Some spi controllers may not support reading up to
>> +			 * erase block size. They will read less data than
>> +			 * expected. If this happen disable continuous mode
>                                              happens,
>
>> +			 * and repeat reading in normal mode.
>> +			 */
>> +			spinand->cont_read_possible = false;
>> +		}
>> +	}
>> +
>> +	if (ret == -E2BIG)
> While I agree with the overall logic, I find pretty unreadable to
> perform the regular read upon a return value that is an error code set
> in the init sequence. Can you please propose an alternate implementation?
>
>>  		ret = spinand_mtd_regular_page_read(mtd, from, ops, &max_bitflips);
>>  
>>  	if (ops->stats) {
> Thanks!
> Miquèl