Re: [PATCH] mtd: rawnand: nand_bbt: Skip bad blocks when searching for the BBT in NAND

[Stefan Riedmüller]

Hi Alexander,

On Wed, 2021-07-07 at 11:18 +0200, Alexander Dahl wrote:
> Hei hei,
> 
> Am Dienstag, 6. Juli 2021, 18:13:08 CEST schrieb Miquel Raynal:
> > Hi Stefan,
> > 
> > Stefan Riedmueller <s.riedmueller@xxxxxxxxx> wrote on Fri, 25 Jun 2021
> > 
> > 14:38:21 +0200:
> > > The blocks containing the bad block table can become bad as well. So
> > > make sure to skip any blocks that are marked bad when searching for the
> > > bad block table.
> > > 
> > > Otherwise in very rare cases where two BBT blocks wear out it might
> > > happen that an obsolete BBT is used instead of a newer available
> > > version.
> > > 
> > > This only applies to drivers which make use of a bad block marker in
> > > flash.
> > > Other drivers won't be able to identify bad BBT blocks and thus can't
> > > skip
> > > these.
> > > 
> > > Signed-off-by: Stefan Riedmueller <s.riedmueller@xxxxxxxxx>
> > 
> > Besides the alignment of the helper parameters (nitpick) the patch
> > looks good to me. If we can get someone to test it before the merge
> > window closes it's perfect. Otherwise I'll apply it and we'll let robots
> > do the job.
> 
> Added the patch on top of v5.10.21 and booted a SAMA5D27 based board, from
> the 
> boot log:
> 
> nand: device found, Manufacturer ID: 0x01, Chip ID: 0xda
> nand: AMD/Spansion S34ML02G1
> nand: 256 MiB, SLC, erase size: 128 KiB, page size: 2048, OOB size: 64
> Bad block table found at page 131008, version 0xFF
> Bad block table found at page 130944, version 0xFF
> 6 cmdlinepart partitions found on MTD device atmel_nand
> Creating 6 MTD partitions on "atmel_nand":
> 0x000000000000-0x000000040000 : "bootstrap"
> 0x000000040000-0x000000100000 : "uboot"
> 0x000000100000-0x000000140000 : "env1"
> 0x000000140000-0x000000180000 : "env2"
> 0x000000180000-0x000000200000 : "reserved"
> 0x000000200000-0x000010000000 : "UBI"
> NET: Registered protocol family 17
> ubi0: attaching mtd5
> random: fast init done
> ubi0: scanning is finished
> ubi0: attached mtd5 (name "UBI", size 254 MiB)
> ubi0: PEB size: 131072 bytes (128 KiB), LEB size: 126976 bytes
> ubi0: min./max. I/O unit sizes: 2048/2048, sub-page size 2048
> ubi0: VID header offset: 2048 (aligned 2048), data offset: 4096
> ubi0: good PEBs: 2028, bad PEBs: 4, corrupted PEBs: 0
> ubi0: user volume: 4, internal volumes: 1, max. volumes count: 128
> ubi0: max/mean erase counter: 4/1, WL threshold: 4096, image sequence
> number: 
> 1600812189
> ubi0: available PEBs: 0, total reserved PEBs: 2028, PEBs reserved for bad
> PEB 
> handling: 36
> ubi0: background thread "ubi_bgt0d" started, PID 85
> 
> No suspicious other messages. 
> 
> Not sure if that device would be affected anyways. No bad blocks are known
> on 
> this flash, device behaves as usual.

Thanks for testing! :)

Regards,
Stefan

> 
> HTH & Greets
> Alex
> 
> > > ---
> > > 
> > > Hi,
> > > 
> > > this is the second approach of this patch. The first one [1]
> > > unfortunately
> > > lead to boot failures on i.MX 27 boards [2] since the i.MX 27 driver
> > > uses
> > > the bad block marker position for the bad block table marker which lead
> > > to falsely identifying all BBT blocks as bad.
> > > 
> > > This new patch now skips the check for bad BBT blocks if the BBT marker
> > > position in OOB overlaps with the bad block marker position or if a
> > > driver
> > > can't use bad block markers in flash at all (NAND_BBT_NO_OOB_BBM or
> > > NAND_NO_BBM_QUIRK are set). This hopefully makes sure we don't break
> > > drivers which cannot check for bad BBT blocks due to the limitations
> > > mentioned before.
> > > 
> > > I was only able to test this patch on a phyCORE-i.MX 6 and a phyCARD-
> > > i.MX
> > > 27. Therfore would really appreciate more people testing this to make
> > > sure I have not missed another use case where the bad block marker
> > > position in OOB is used in a different way than for the BBM.
> > > 
> > > Regards,
> > > Stefan
> > > 
> > > [1]
> > > https://lore.kernel.org/linux-mtd/20210325102337.481172-1-s.riedmueller@p
> > > hytec.de/ [2]
> > > https://lore.kernel.org/linux-mtd/CAOMZO5DufVR=+EzCa1-MPUc+ZefZVTXb5Kgu3W
> > > xms7cxw9GmGg@xxxxxxxxxxxxxx/> 
> > >  drivers/mtd/nand/raw/nand_bbt.c | 34 +++++++++++++++++++++++++++++++++
> > >  1 file changed, 34 insertions(+)
> > > 
> > > diff --git a/drivers/mtd/nand/raw/nand_bbt.c
> > > b/drivers/mtd/nand/raw/nand_bbt.c index dced32a126d9..2a30714350ee
> > > 100644
> > > --- a/drivers/mtd/nand/raw/nand_bbt.c
> > > +++ b/drivers/mtd/nand/raw/nand_bbt.c
> > > @@ -447,6 +447,36 @@ static int scan_block_fast(struct nand_chip *this,
> > > struct nand_bbt_descr *bd,> 
> > >  	return 0;
> > >  
> > >  }
> > > 
> > > +/* Check if a potential BBT block is marked as bad */
> > > +static int bbt_block_checkbad(struct nand_chip *this,
> > > +				      struct nand_bbt_descr *td,
> > > +				      loff_t offs, uint8_t *buf)
> > > +{
> > > +	struct nand_bbt_descr *bd = this->badblock_pattern;
> > > +
> > > +	/*
> > > +	 * No need to check for a bad BBT block if the BBM area overlaps with
> > > +	 * the bad block table marker area in OOB since writing a BBM here
> > > +	 * invalidates the bad block table marker anyway.
> > > +	 */
> > > +	if (!(td->options & NAND_BBT_NO_OOB) &&
> > > +	    td->offs >= bd->offs && td->offs < bd->offs + bd->len)
> > > +		return 0;
> > > +
> > > +	/*
> > > +	 * There is no point in checking for a bad block marker if writing
> > > +	 * such marker is not supported
> > > +	 */
> > > +	if (this->bbt_options & NAND_BBT_NO_OOB_BBM ||
> > > +	    this->options & NAND_NO_BBM_QUIRK)
> > > +		return 0;
> > > +
> > > +	if (scan_block_fast(this, bd, offs, buf) > 0)
> > > +		return 1;
> > > +
> > > +	return 0;
> > > +}
> > > +
> > > 
> > >  /**
> > >  
> > >   * create_bbt - [GENERIC] Create a bad block table by scanning the
> > > device
> > >   * @this: NAND chip object
> > > 
> > > @@ -560,6 +590,10 @@ static int search_bbt(struct nand_chip *this,
> > > uint8_t
> > > *buf,> 
> > >  			int actblock = startblock + dir * block;
> > >  			loff_t offs = (loff_t)actblock << this-
> > > >bbt_erase_shift;
> > > 
> > > +			/* Check if block is marked bad */
> > > +			if (bbt_block_checkbad(this, td, offs, buf))
> > > +				continue;
> > > +
> > > 
> > >  			/* Read first page */
> > >  			scan_read(this, buf, offs, mtd->writesize, td);
> > >  			if (!check_pattern(buf, scanlen, mtd->writesize, td))
> > > {
> > 
> > Thanks,
> > Miquèl
> > 
> > ______________________________________________________
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> > http://lists.infradead.org/mailman/listinfo/linux-mtd/
> 
> 
>