nand: reinstate lazy bad block scanning

commit 2a8e0fc8b3dc31a3c571e439fbf04b882c8986be ("nand: Merge changes
from Linux nand driver") accidentally reverted commit
13f0fd94e3cae6f8a0d9fba5d367e311edc8ebde ("NAND: Scan bad blocks
lazily.").

Reinstate the change, as amended by commit
ff49ea8977b56916edd5b1766d9939010e30b181 ("NAND: Mark the BBT as scanned
prior to calling scan_bbt.").

Signed-off-by: Scott Wood <scottwood@freescale.com>

drivers/mtd/nand/nand_base.c

@@ -479,6 +479,11 @@ static int nand_block_checkbad(struct mtd_info *mtd, loff_t ofs, int getchip,
 {
 	struct nand_chip *chip = mtd->priv;
 
+	if (!(chip->options & NAND_BBT_SCANNED)) {
+		chip->options |= NAND_BBT_SCANNED;
+		chip->scan_bbt(mtd);
+	}
+
 	if (!chip->bbt)
 		return chip->block_bad(mtd, ofs, getchip);
 
@@ -3166,10 +3171,9 @@ int nand_scan_tail(struct mtd_info *mtd)
 
 	/* Check, if we should skip the bad block table scan */
 	if (chip->options & NAND_SKIP_BBTSCAN)
-		return 0;
+		chip->options |= NAND_BBT_SCANNED;
 
-	/* Build bad block table */
-	return chip->scan_bbt(mtd);
+	return 0;
 }
 
 /**

include/linux/mtd/nand.h

@@ -232,6 +232,8 @@ typedef enum {
 #define NAND_CREATE_EMPTY_BBT		0x01000000
 
 /* Options set by nand scan */
+/* bbt has already been read */
+#define NAND_BBT_SCANNED	0x40000000
 /* Nand scan has allocated controller struct */
 #define NAND_CONTROLLER_ALLOC	0x80000000