mtd: nand-imx: Create BBT automatically when necessary

Due to the differences of the logical page format and the raw page
format on NAND the generic nand support can't read the bad block
marker on the NAND. For this reason we have the imx_nand_bbm command
which knows about these specialities and creates a BBT. The problem
with this command is that one has to call it and experience shows
this is often forgotten. Linux will then create a BBT based on wrong
informations and the real bad blocks may be lost.

With this patch we automatically create a BBT when none is found and
make the command unnecssary.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

1 files changed, 102 insertions, 1 deletions

diff --git a/drivers/mtd/nand/nand_imx.c b/drivers/mtd/nand/nand_imx.c
index 8e1558da6b..cb5b7ee151 100644
--- a/drivers/mtd/nand/nand_imx.c
+++ b/drivers/mtd/nand/nand_imx.c
@@ -1117,6 +1117,102 @@ static int __init mxcnd_probe_dt(struct imx_nand_host *host)
 }
 
 /*
+ * The i.MX NAND controller has the problem that it handles the
+ * data in chunks of 512 bytes. It doesn't treat 2k NAND chips as
+ * 2048 byte data + 64 OOB, but instead:
+ *
+ * 512b data + 16b OOB +
+ * 512b data + 16b OOB +
+ * 512b data + 16b OOB +
+ * 512b data + 16b OOB
+ *
+ * This means that the factory provided bad block marker ends up
+ * in the page data at offset 2000 instead of in the OOB data.
+ *
+ * To preserve the factory bad block information we take the following
+ * strategy:
+ *
+ * - If the NAND driver detects that no flash BBT is present on 2k NAND
+ *   chips it will not create one because it would do so based on the wrong
+ *   BBM position
+ * - This command is used to create a flash BBT then.
+ *
+ * From this point on we can forget about the BBMs and rely completely
+ * on the flash BBT.
+ *
+ */
+static int checkbad(struct mtd_info *mtd, loff_t ofs)
+{
+	int ret;
+	uint8_t buf[mtd->writesize + mtd->oobsize];
+	struct mtd_oob_ops ops;
+
+	ops.mode = MTD_OPS_RAW;
+	ops.ooboffs = 0;
+	ops.datbuf = buf;
+	ops.len = mtd->writesize;
+	ops.oobbuf = buf + mtd->writesize;
+	ops.ooblen = mtd->oobsize;
+
+	ret = mtd_read_oob(mtd, ofs, &ops);
+	if (ret < 0)
+		return ret;
+
+	if (buf[2000] != 0xff)
+		return 1;
+
+	return 0;
+}
+
+static int imxnd_create_bbt(struct mtd_info *mtd)
+{
+	struct nand_chip *chip = mtd_to_nand(mtd);
+	int len, i, numblocks, ret;
+	loff_t from = 0;
+	uint8_t *bbt;
+
+	len = mtd->size >> (chip->bbt_erase_shift + 2);
+
+	/* Allocate memory (2bit per block) and clear the memory bad block table */
+	bbt = kzalloc(len, GFP_KERNEL);
+	if (!bbt)
+		return -ENOMEM;
+
+	numblocks = mtd->size >> (chip->bbt_erase_shift - 1);
+
+	for (i = 0; i < numblocks;) {
+		ret = checkbad(mtd, from);
+		if (ret < 0)
+			goto out;
+
+		if (ret) {
+			bbt[i >> 3] |= 0x03 << (i & 0x6);
+			dev_info(mtd->parent, "Bad eraseblock %d at 0x%08x\n",
+				 i >> 1, (unsigned int)from);
+		}
+
+		i += 2;
+		from += (1 << chip->bbt_erase_shift);
+	}
+
+	chip->bbt_td->options |= NAND_BBT_CREATE;
+	chip->bbt_md->options |= NAND_BBT_CREATE;
+
+	free(chip->bbt);
+	chip->bbt = bbt;
+
+	ret = nand_update_bbt(mtd, 0);
+	if (ret)
+		return ret;
+
+	ret = 0;
+out:
+	free(bbt);
+
+	return ret;
+}
+
+/*
  * This function is called during the driver binding process.
  *
  * @param   pdev  the device structure used to store device specific
@@ -1329,7 +1425,12 @@ static int __init imxnd_probe(struct device_d *dev)
 	}
 
 	if (host->flash_bbt && this->bbt_td->pages[0] == -1 && this->bbt_md->pages[0] == -1) {
-		dev_warn(dev, "no BBT found. create one using the imx_nand_bbm command\n");
+		dev_info(dev, "no BBT found. creating one\n");
+		err = imxnd_create_bbt(mtd);
+		if (err)
+			dev_warn(dev, "Failed to create bbt: %s\n",
+				 strerror(-err));
+		err = 0;
 	}
 
 	add_mtd_nand_device(mtd, "nand");