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

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Message-ID: <f03d93a5-4393-2405-b597-80b762059f01@kontron.de>
Date:   Thu, 19 Sep 2019 13:15:08 +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 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;

         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
>