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

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Message-ID: <20190919151820.2bb8313d@xps13>
Date:   Thu, 19 Sep 2019 15:18:20 +0200
From:   Miquel Raynal <miquel.raynal@...tlin.com>
To:     Schrempf Frieder <frieder.schrempf@...tron.de>
Cc:     Piotr Sroka <piotrs@...ence.com>,
        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

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.

> 
>          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