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

Hi,

Brian Norris wrote:

Hi Lothar,

On Thu, Jun 12, 2014 at 03:20:45PM +0200, Lothar Wa?mann wrote:

quoted

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:

quoted

Signed-off-by: Lothar Wa?mann <redacted>
---
 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.

quoted

+	.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.

quoted

+	.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 Wa?mann
-- 
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