[PATCH v2 2/3] mtd: nand: implement 'max_bad_blocks' mtd function

[Zach Brown]

From: Jeff Westfahl <jeff.westfahl@xxxxxx>

Implement the new mtd function 'max_bad_blocks'. Use the ONFI parameter
page to find the maximum bad blocks to reserve for an MTD, taking into
account how many LUNs the MTD spans.

Signed-off-by: Jeff Westfahl <jeff.westfahl@xxxxxx>
Signed-off-by: Zach Brown <zach.brown@xxxxxx>
---
 drivers/mtd/nand/nand_base.c | 34 ++++++++++++++++++++++++++++++++++
 1 file changed, 34 insertions(+)

diff --git a/drivers/mtd/nand/nand_base.c b/drivers/mtd/nand/nand_base.c
index e5718e5..ac08224 100644
--- a/drivers/mtd/nand/nand_base.c
+++ b/drivers/mtd/nand/nand_base.c
@@ -3226,6 +3226,39 @@ static int nand_block_markbad(struct mtd_info *mtd, loff_t ofs)
 }
 
 /**
+ * nand_max_bad_blocks - [MTD Interface] Max number of bad blocks for an mtd
+ * @mtd: MTD device structure
+ * @ofs: offset relative to mtd start
+ * @len: length of mtd
+ */
+static int nand_max_bad_blocks(struct mtd_info *mtd, loff_t ofs, size_t len)
+{
+	struct nand_chip *chip = mtd_to_nand(mtd);
+	uint32_t part_start_block;
+	uint32_t part_end_block;
+	uint32_t part_start_lun;
+	uint32_t part_end_lun;
+
+	/* ONFI is used to determine the maximum bad block count. */
+	if (!chip->onfi_version)
+		return -ENOTSUPP;
+
+	/* Get the start and end of the partition in erase blocks. */
+	part_start_block = mtd_div_by_eb(ofs, mtd);
+	part_end_block = mtd_div_by_eb(len, mtd) + part_start_block - 1;
+
+	/* Get the start and end LUNs of the partition. */
+	part_start_lun = part_start_block / chip->onfi_params.blocks_per_lun;
+	part_end_lun = part_end_block / chip->onfi_params.blocks_per_lun;
+
+	/* Look up the bad blocks per unit and multiply by the number of units
+	 * that the partition spans.
+	 */
+	return chip->onfi_params.bb_per_lun *
+		(part_end_lun - part_start_lun + 1);
+}
+
+/**
  * nand_onfi_set_features- [REPLACEABLE] set features for ONFI nand
  * @mtd: MTD device structure
  * @chip: nand chip info structure
@@ -4743,6 +4776,7 @@ int nand_scan_tail(struct mtd_info *mtd)
 	mtd->_block_isreserved = nand_block_isreserved;
 	mtd->_block_isbad = nand_block_isbad;
 	mtd->_block_markbad = nand_block_markbad;
+	mtd->_max_bad_blocks = nand_max_bad_blocks;
 	mtd->writebufsize = mtd->writesize;
 
 	/*
-- 
2.7.4