linux-kernel - Re: mtd: spinand: add spi nand mtd resume handler

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Message-ID: <3baf8f02-f290-91d1-af56-62181651c61a@foss.st.com>
Date:   Thu, 27 May 2021 15:50:23 +0200
From:   Patrice CHOTARD <patrice.chotard@...s.st.com>
To:     Pratyush Yadav <p.yadav@...com>
CC:     Mark Brown <broonie@...nel.org>,
        Miquel Raynal <miquel.raynal@...tlin.com>,
        Vignesh Raghavendra <vigneshr@...com>,
        Boris Brezillon <boris.brezillon@...labora.com>,
        <linux-mtd@...ts.infradead.org>,
        Alexandre Torgue <alexandre.torgue@...s.st.com>,
        <linux-spi@...r.kernel.org>,
        <linux-stm32@...md-mailman.stormreply.com>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>, <christophe.kerello@...s.st.com>
Subject: Re: mtd: spinand: add spi nand mtd resume handler

Hi Pratyush

On 5/27/21 12:00 PM, Pratyush Yadav wrote:
> On 26/05/21 05:30PM, patrice.chotard@...s.st.com wrote:
>> From: Christophe Kerello <christophe.kerello@...s.st.com>
>>
>> After power up, all SPI NAND's blocks are locked. Only read operations
>> are allowed, write and erase operations are forbidden.
>> The SPI NAND framework unlocks all the blocks during its initialization.
>>
>> During a standby low power, the memory is powered down, losing its
>> configuration.
>> During the resume, the QSPI driver state is restored but the SPI NAND
>> framework does not reconfigured the memory.
>>
>> This patch adds spi nand mtd PM handlers for resume ops.
>> SPI NAND resume op re-initializes SPI NAND flash to its probed state.
>>
>> Signed-off-by: Christophe Kerello <christophe.kerello@...s.st.com>
>> Signed-off-by: Patrice Chotard <patrice.chotard@...s.st.com>
>> ---
>>  drivers/mtd/nand/spi/core.c | 56 +++++++++++++++++++++++++++++++++++++
>>  1 file changed, 56 insertions(+)
>>
>> diff --git a/drivers/mtd/nand/spi/core.c b/drivers/mtd/nand/spi/core.c
>> index 17f63f95f4a2..6abaf874eb3f 100644
>> --- a/drivers/mtd/nand/spi/core.c
>> +++ b/drivers/mtd/nand/spi/core.c
>> @@ -1074,6 +1074,61 @@ static int spinand_detect(struct spinand_device *spinand)
>>  	return 0;
>>  }
>>  
>> +static void spinand_mtd_resume(struct mtd_info *mtd)
>> +{
>> +	struct spinand_device *spinand = mtd_to_spinand(mtd);
>> +	struct nand_device *nand = mtd_to_nanddev(mtd);
>> +	struct device *dev = &spinand->spimem->spi->dev;
>> +	int ret, i;
>> +
>> +	ret = spinand_reset_op(spinand);
>> +	if (ret)
>> +		return;
>> +
>> +	ret = spinand_init_quad_enable(spinand);
>> +	if (ret) {
>> +		dev_err(dev,
>> +			"Failed to initialize the quad part (err = %d)\n",
>> +			ret);
>> +		return;
>> +	}
>> +
>> +	ret = spinand_upd_cfg(spinand, CFG_OTP_ENABLE, 0);
>> +	if (ret) {
>> +		dev_err(dev,
>> +			"Failed to updtae the OTP (err = %d)\n",
>> +			ret);
>> +		return;
>> +	}
> 
> Since you have reset the flash, this cache is invalid. You should reset 
> the cache and re-populate it before using it in any way.

I got your point, i will take it in account in v3 (v2 has already been send but need rework)

> 
>> +
>> +	ret = spinand_manufacturer_init(spinand);
>> +	if (ret) {
>> +		dev_err(dev,
>> +			"Failed to initialize the SPI NAND chip (err = %d)\n",
>> +			ret);
>> +		return;
>> +	}
>> +
>> +	/* After power up, all blocks are locked, so unlock them here. */
>> +	for (i = 0; i < nand->memorg.ntargets; i++) {
>> +		ret = spinand_select_target(spinand, i);
>> +		if (ret) {
>> +			dev_err(dev,
>> +				"Failed to select the target (err = %d)\n",
>> +				ret);
>> +			return;
>> +		}
>> +
>> +		ret = spinand_lock_block(spinand, BL_ALL_UNLOCKED);
>> +		if (ret) {
>> +			dev_err(dev,
>> +				"Failed to unlock block (err = %d)\n",
>> +				ret);
>> +			return;
>> +		}
>> +	}
>> +}
>> +
> 
> Most of these seem to be copied from spinand_init(). I think it is 
> better to create a common function that can be called from both 
> spinand_init() and spinand_mtd_resume(). This way when someone adds 
> something new to the init procedure, like support for some other modes, 
> they won't have to remember to update it in two places.

Agree, it was already part of the v2

> 
>>  static int spinand_init(struct spinand_device *spinand)
>>  {
>>  	struct device *dev = &spinand->spimem->spi->dev;
>> @@ -1167,6 +1222,7 @@ static int spinand_init(struct spinand_device *spinand)
>>  	mtd->_block_isreserved = spinand_mtd_block_isreserved;
>>  	mtd->_erase = spinand_mtd_erase;
>>  	mtd->_max_bad_blocks = nanddev_mtd_max_bad_blocks;
>> +	mtd->_resume = spinand_mtd_resume;
> 
> Is it possible that the userspace can use this mtd device before the 
> resume is finished? Is there a way to temporarily "pause" or unregister 
> an mtd device?

Honestly, i don't know.

Thanks
Patrice

> 
>>  
>>  	if (nand->ecc.engine) {
>>  		ret = mtd_ooblayout_count_freebytes(mtd);
>