linux-kernel - Re: [PATCH] - change calculating of position page containing BBM

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Date:   Thu, 19 Sep 2019 13:33:01 +0000
From:   Schrempf Frieder <frieder.schrempf@...tron.de>
To:     Miquel Raynal <miquel.raynal@...tlin.com>,
        Piotr Sroka <piotrs@...ence.com>
CC:     Richard Weinberger <richard@....at>,
        David Woodhouse <dwmw2@...radead.org>,
        Brian Norris <computersforpeace@...il.com>,
        "Marek Vasut" <marek.vasut@...il.com>,
        Vignesh Raghavendra <vigneshr@...com>,
        "Boris Brezillon" <bbrezillon@...nel.org>,
        "linux-mtd@...ts.infradead.org" <linux-mtd@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] - change calculating of position page containing BBM

On 19.09.19 15:18, Miquel Raynal wrote:
> Hello,
> 
> Schrempf Frieder <frieder.schrempf@...tron.de> wrote on Thu, 19 Sep
> 2019 13:15:08 +0000:
> 
>> On 19.09.19 14:58, Miquel Raynal wrote:
>>> Hi Piotr,
>>>
>>> Piotr Sroka <piotrs@...ence.com> wrote on Thu, 19 Sep 2019 13:41:35
>>> +0100:
>>>    
>>>> Change calculating of position page containing BBM
>>>>
>>>> If none of BBM flags is set then function nand_bbm_get_next_page
>>>> reports EINVAL. It causes that BBM is not read at all during scanning
>>>> factory bad blocks. The result is that the BBT table is build without
>>>> checking factory BBM at all. For Micron flash memories none of this
>>>> flag is set if page size is different than 2048 bytes.
>>
>> I wonder if it wouldn't be better to fix the Micron driver instead:
>>
>> --- a/drivers/mtd/nand/raw/nand_micron.c
>> +++ b/drivers/mtd/nand/raw/nand_micron.c
>> @@ -448,6 +448,8 @@ static int micron_nand_init(struct nand_chip *chip)
>>
>>           if (mtd->writesize == 2048)
>>                   chip->options |= NAND_BBM_FIRSTPAGE |
>>                                    NAND_BBM_SECONDPAGE;
>> +       else
>> +               chip->options |= NAND_BBM_FIRSTPAGE;
> 
> That's what I forgot in my last answer to this thread, I think I only
> told Piotr privately: I would like both. I think it is important to fix
> the bbm_get_next_page function but for clarity, setting the FIRSTPAGE
> flag in Micron's driver seems also pertinent.

Indeed, that sounds reasonable. Piotr, can you send another patch with 
the diff above? And by the way: thanks for fixing my code ;)

Reviewed-by: Frieder Schrempf <frieder.schrempf@...tron.de>

> 
>>
>>           ondie = micron_supports_on_die_ecc(chip);
>>
>>
>>>
>>> "none of these flags are set"
>>>    
>>>>
>>>> This patch changes the nand_bbm_get_next_page function.
>>>
>>> "Address this regression by changing the
>>> nand_bbm_get_next_page_function."
>>>    
>>>> It will return 0 if none of BBM flag is set and page parameter is 0.
>>>
>>>                         no BBM flag is set
>>>    
>>>> After that modification way of discovering factory bad blocks will work
>>>> similar as in kernel version 5.1.
>>>>   
>>>
>>> Fixes + stable tags would be great!
>>>    
>>>> Signed-off-by: Piotr Sroka <piotrs@...ence.com>
>>>> ---
>>>>    drivers/mtd/nand/raw/nand_base.c | 8 ++++++--
>>>>    1 file changed, 6 insertions(+), 2 deletions(-)
>>>>
>>>> diff --git a/drivers/mtd/nand/raw/nand_base.c b/drivers/mtd/nand/raw/nand_base.c
>>>> index 5c2c30a7dffa..f64e3b6605c6 100644
>>>> --- a/drivers/mtd/nand/raw/nand_base.c
>>>> +++ b/drivers/mtd/nand/raw/nand_base.c
>>>> @@ -292,12 +292,16 @@ int nand_bbm_get_next_page(struct nand_chip *chip, int page)
>>>>    	struct mtd_info *mtd = nand_to_mtd(chip);
>>>>    	int last_page = ((mtd->erasesize - mtd->writesize) >>
>>>>    			 chip->page_shift) & chip->pagemask;
>>>> +	unsigned int bbm_flags = NAND_BBM_FIRSTPAGE | NAND_BBM_SECONDPAGE
>>>> +		| NAND_BBM_LASTPAGE;
>>>>    
>>>> +	if (page == 0 && !(chip->options & bbm_flags))
>>>> +		return 0;
>>>>    	if (page == 0 && chip->options & NAND_BBM_FIRSTPAGE)
>>>>    		return 0;
>>>> -	else if (page <= 1 && chip->options & NAND_BBM_SECONDPAGE)
>>>> +	if (page <= 1 && chip->options & NAND_BBM_SECONDPAGE)
>>>>    		return 1;
>>>> -	else if (page <= last_page && chip->options & NAND_BBM_LASTPAGE)
>>>> +	if (page <= last_page && chip->options & NAND_BBM_LASTPAGE)
>>>>    		return last_page;
>>>>    
>>>>    	return -EINVAL;
>>>
>>> Lookgs good otherwise.
>>>
>>> Thanks,
>>> Miquèl
>>>   
> 
> Thanks,
> Miquèl
>