Re: [PATCHv4 5/5] mtd: gpmi: prevent creating a new BBT when blockmark swapping is disabled

Lothar Waßmann
2014-07-29T06:34:21Z

Hi,

Brian Norris wrote:
> Hi Lothar,
>
> On Thu, Jun 12, 2014 at 03:20:45PM +0200, Lothar Waßmann wrote:
> > Without blockmark swapping, there is no use in creating a BBT from
> > scratch, so use a BBT descriptor with NAND_BBT_CREATE unset in this
> > case.
>
> I'm curious: what is your plan if there is no BBT available on your
> device, or if it ever gets corrupted? IIUC, nand_bbt will just assume
> you have no bad blocks, and it will never write a bad block table to
> flash. This also means no subsequent discoverable bad blocks can be
> recorded across power cycles, I believe.
>
That won't happen (unless it's not possible to create a BBT because all
the possible blocks for the BBT are bad), because the bootloader will
have created one before Linux is started.

> Maybe you don't want to specify your own nand_bbt_descr's at all, but
> you just need to set:
>
> chip->bbt_options |= NAND_BBT_CREATE_EMPTY | NAND_BBT_NO_OOB;
>
> (Note: there's a little bit of fuzziness about NAND_BBT_* flags, where
> some are targeted for the nand_chip::bbt_options field, and others
> belong in struct nand_bbt_descr::options.)
>
> But if for some reason we need to keep this patch, a comment below:
>
> > Signed-off-by: Lothar Waßmann <LW@KARO-electronics.de>
> > ---
> > drivers/mtd/nand/gpmi-nand/gpmi-nand.c | 28 +++++++++++++++++++++++++++-
> > 1 file changed, 27 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/mtd/nand/gpmi-nand/gpmi-nand.c b/drivers/mtd/nand/gpmi-nand/gpmi-nand.c
> > index 37537b4..fc710d7 100644
> > --- a/drivers/mtd/nand/gpmi-nand/gpmi-nand.c
> > +++ b/drivers/mtd/nand/gpmi-nand/gpmi-nand.c
> > @@ -43,6 +43,29 @@ static struct nand_bbt_descr gpmi_bbt_descr = {
> > .pattern = scan_ff_pattern
> > };
> >
> > +static uint8_t bbt_pattern[] = {'B', 'b', 't', '0' };
> > +static uint8_t mirror_pattern[] = {'1', 't', 'b', 'B' };
> > +
> > +static struct nand_bbt_descr bbt_main_no_oob_descr = {
> > + .options = NAND_BBT_LASTBLOCK | NAND_BBT_WRITE |
> > + NAND_BBT_2BIT | NAND_BBT_VERSION | NAND_BBT_PERCHIP |
> > + NAND_BBT_NO_OOB,
>
> Please indent the above two lines a bit, preferably matching the
> indentation of NAND_BBT_LASTBLOCK. It should be clear that this is a
> continuation of the '.options' initialization.
>
OK.

> > + .len = 4,
> > + .veroffs = 4,
> > + .maxblocks = NAND_BBT_SCAN_MAXBLOCKS,
> > + .pattern = bbt_pattern,
> > +};
> > +
> > +static struct nand_bbt_descr bbt_mirror_no_oob_descr = {
> > + .options = NAND_BBT_LASTBLOCK | NAND_BBT_WRITE |
> > + NAND_BBT_2BIT | NAND_BBT_VERSION | NAND_BBT_PERCHIP |
> > + NAND_BBT_NO_OOB,
>
> Same here.
>
> > + .len = 4,
> > + .veroffs = 4,
> > + .maxblocks = NAND_BBT_SCAN_MAXBLOCKS,
> > + .pattern = mirror_pattern,
> > +};
> > +
> > /*
> > * We may change the layout if we can get the ECC info from the datasheet,
> > * else we will use all the (page + OOB).
> > @@ -1728,8 +1751,11 @@ static int gpmi_nand_init(struct gpmi_nand_data *this)
> > chip->bbt_options |= NAND_BBT_NO_OOB_BBM;
> >
> > if (of_property_read_bool(this->dev->of_node,
> > - "fsl,no-blockmark-swap"))
> > + "fsl,no-blockmark-swap")) {
> > this->swap_block_mark = false;
> > + chip->bbt_td = &bbt_main_no_oob_descr;
> > + chip->bbt_md = &bbt_mirror_no_oob_descr;
>
> My initial recommendation for this patch and the previous patch means
> that you could just drop both patches and replace them with the
> following:
>
> /* Comment here to explain why... */
> chip->bbt_options |= NAND_BBT_CREATE_EMPTY |
> NAND_BBT_NO_OOB |
> NAND_BBT_NO_OOB_BBM;
OK.

Lothar Waßmann
--
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