mtd: nand: fix SCAN2NDPAGE check for BBM

nand_block_bad() doesn't check the correct pages when
NAND_BBT_SCAN2NDPAGE is enabled. It should scan both the OOB region of
both the 1st and 2nd page of each block.
Signed-off-by: Brian Norris <computersforpeace@gmail.com>
Signed-off-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>

drivers/mtd/nand/nand_base.c

@@ -338,7 +338,7 @@ static int nand_verify_buf16(struct mtd_info *mtd, const uint8_t *buf, int len)
  */
 static int nand_block_bad(struct mtd_info *mtd, loff_t ofs, int getchip)
 {
-	int page, chipnr, res = 0;
+	int page, chipnr, res = 0, i = 0;
 	struct nand_chip *chip = mtd->priv;
 	u16 bad;
 
@@ -356,23 +356,29 @@ static int nand_block_bad(struct mtd_info *mtd, loff_t ofs, int getchip)
 		chip->select_chip(mtd, chipnr);
 	}
 
-	if (chip->options & NAND_BUSWIDTH_16) {
-		chip->cmdfunc(mtd, NAND_CMD_READOOB, chip->badblockpos & 0xFE,
-			      page);
-		bad = cpu_to_le16(chip->read_word(mtd));
-		if (chip->badblockpos & 0x1)
-			bad >>= 8;
-		else
-			bad &= 0xFF;
-	} else {
-		chip->cmdfunc(mtd, NAND_CMD_READOOB, chip->badblockpos, page);
-		bad = chip->read_byte(mtd);
-	}
+	do {
+		if (chip->options & NAND_BUSWIDTH_16) {
+			chip->cmdfunc(mtd, NAND_CMD_READOOB,
+					chip->badblockpos & 0xFE, page);
+			bad = cpu_to_le16(chip->read_word(mtd));
+			if (chip->badblockpos & 0x1)
+				bad >>= 8;
+			else
+				bad &= 0xFF;
+		} else {
+			chip->cmdfunc(mtd, NAND_CMD_READOOB, chip->badblockpos,
+					page);
+			bad = chip->read_byte(mtd);
+		}
 
-	if (likely(chip->badblockbits == 8))
-		res = bad != 0xFF;
-	else
-		res = hweight8(bad) < chip->badblockbits;
+		if (likely(chip->badblockbits == 8))
+			res = bad != 0xFF;
+		else
+			res = hweight8(bad) < chip->badblockbits;
+		ofs += mtd->writesize;
+		page = (int)(ofs >> chip->page_shift) & chip->pagemask;
+		i++;
+	} while (!res && i < 2 && (chip->bbt_options & NAND_BBT_SCAN2NDPAGE));
 
 	if (getchip)
 		nand_release_device(mtd);