linux-kernel - Re: [PATCH 3/3] mtd: spinand: Wait for the erase op to finish before writing a bad block marker

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Date:   Mon, 17 Feb 2020 11:29:50 +0000
From:   Schrempf Frieder <frieder.schrempf@...tron.de>
To:     Boris Brezillon <boris.brezillon@...labora.com>,
        Miquel Raynal <miquel.raynal@...tlin.com>
CC:     Boris Brezillon <bbrezillon@...nel.org>,
        Jeff Kletsky <git-commits@...ycomm.com>,
        liaoweixiong <liaoweixiong@...winnertech.com>,
        "stable@...r.kernel.org" <stable@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-mtd@...ts.infradead.org" <linux-mtd@...ts.infradead.org>,
        "Richard Weinberger" <richard@....at>
Subject: Re: [PATCH 3/3] mtd: spinand: Wait for the erase op to finish before
 writing a bad block marker

Hi Boris,

On 17.02.20 12:14, Boris Brezillon wrote:
> On Mon, 17 Feb 2020 11:39:19 +0100
> Miquel Raynal <miquel.raynal@...tlin.com> wrote:
> 
>> Hi Frieder,
>>
>> Schrempf Frieder <frieder.schrempf@...tron.de> wrote on Tue, 11 Feb
>> 2020 16:35:53 +0000:
>>
>>> From: Frieder Schrempf <frieder.schrempf@...tron.de>
>>>
>>> Currently when marking a block, we use spinand_erase_op() to erase
>>> the block before writing the marker to the OOB area without waiting
>>> for the operation to succeed. This can lead to the marking failing
>>> silently and no bad block marker being written to the flash.
>>>
>>> To fix this we reuse the spinand_erase() function, that already does
>>> everything we need to do before actually writing the marker.
>>>    
>>
>> Thanks a lot for this series!
>>
>> Yet I don't really understand the point of waiting for the erasure if
>> it failed: we don't really care as programming (1 -> 0) cells is always
>> possible. Are you sure this lead to an error?
> 
> Actually, I think I already pointed out that we should probably write
> the BBM without erasing the block. IIRC, this logic has been copied
> from rawnand where some controllers don't disable the ECC engine when
> doing raw accesses, leading to ECC errors if the block is not erased
> before BBMs are programmed. Assuming we don't let such drivers being
> merged in spinand, this erase operation can be dropped.

You're probably right, we could also just write the BBM without erasing 
the block. I will try if this works in my setup and update the patch.

> 
>>
>> Also, why just not calling spinand_erase() instead of
>> spinand_erase_op() from spinand_markbad()?
>>
>>> Fixes: 7529df465248 ("mtd: nand: Add core infrastructure to support SPI NANDs")
>>> Cc: stable@...r.kernel.org
>>> Signed-off-by: Frieder Schrempf <frieder.schrempf@...tron.de>
>>> ---
>>>   drivers/mtd/nand/spi/core.c | 56 ++++++++++++++++++-------------------
>>>   1 file changed, 28 insertions(+), 28 deletions(-)
>>>
>>> diff --git a/drivers/mtd/nand/spi/core.c b/drivers/mtd/nand/spi/core.c
>>> index 925db6269861..8a69d13639e2 100644
>>> --- a/drivers/mtd/nand/spi/core.c
>>> +++ b/drivers/mtd/nand/spi/core.c
>>> @@ -600,6 +600,32 @@ static int spinand_mtd_block_isbad(struct mtd_info *mtd, loff_t offs)
>>>   	return ret;
>>>   }
>>>   
>>> +static int __spinand_erase(struct nand_device *nand, const struct nand_pos *pos,
>>> +			   bool hard_fail)
> 
> I hate those __ prefix. Please find a more descriptive name
> (spinand_erase_block() or spinand_erase_and_wait()?)

Actually I was expecting this comment ;)
And I totally agree. I was just lazy to come up with a name.
If we follow the approach without erase, I can get rid of this anyway.

Thanks,
Frieder

> 
>>> +{
>>> +	struct spinand_device *spinand = nand_to_spinand(nand);
>>> +	u8 status;
>>> +	int ret;
>>> +
>>> +	ret = spinand_select_target(spinand, pos->target);
>>> +	if (ret)
>>> +		return ret;
>>> +
>>> +	ret = spinand_write_enable_op(spinand);
>>> +	if (ret)
>>> +		return ret;
>>> +
>>> +	ret = spinand_erase_op(spinand, pos);
>>> +	if (ret && hard_fail)
>>> +		return ret;
>>> +
>>> +	ret = spinand_wait(spinand, &status);
>>> +	if (!ret && (status & STATUS_ERASE_FAILED))
>>> +		ret = -EIO;
>>> +
>>> +	return ret;
>>> +}
>>> +
>>>   static int spinand_markbad(struct nand_device *nand, const struct nand_pos *pos)
>>>   {
>>>   	struct spinand_device *spinand = nand_to_spinand(nand);
>>> @@ -614,16 +640,10 @@ static int spinand_markbad(struct nand_device *nand, const struct nand_pos *pos)
>>>   	int ret;
>>>   
>>>   	/* Erase block before marking it bad. */
>>> -	ret = spinand_select_target(spinand, pos->target);
>>> -	if (ret)
>>> -		return ret;
>>> -
>>> -	ret = spinand_write_enable_op(spinand);
>>> +	ret = __spinand_erase(nand, pos, false);
>>>   	if (ret)
>>>   		return ret;
>>>   
>>> -	spinand_erase_op(spinand, pos);
>>> -
>>>   	return spinand_write_page(spinand, &req);
>>>   }
>>>   
>>> @@ -644,27 +664,7 @@ static int spinand_mtd_block_markbad(struct mtd_info *mtd, loff_t offs)
>>>   
>>>   static int spinand_erase(struct nand_device *nand, const struct nand_pos *pos)
>>>   {
>>> -	struct spinand_device *spinand = nand_to_spinand(nand);
>>> -	u8 status;
>>> -	int ret;
>>> -
>>> -	ret = spinand_select_target(spinand, pos->target);
>>> -	if (ret)
>>> -		return ret;
>>> -
>>> -	ret = spinand_write_enable_op(spinand);
>>> -	if (ret)
>>> -		return ret;
>>> -
>>> -	ret = spinand_erase_op(spinand, pos);
>>> -	if (ret)
>>> -		return ret;
>>> -
>>> -	ret = spinand_wait(spinand, &status);
>>> -	if (!ret && (status & STATUS_ERASE_FAILED))
>>> -		ret = -EIO;
>>> -
>>> -	return ret;
>>> +	return __spinand_erase(nand, pos, true);
>>>   }
>>>   
>>>   static int spinand_mtd_erase(struct mtd_info *mtd,
>>
>> Thanks,
>> Miquèl
>