[RFC 25/47] mtd: nand: stm_nand_bch: bad block marking helpers

[Lee Jones]

Bad Block Markers (BBMs) keep track of unusable/unsuitable memory
blocks which can prevent unnecessary data loss. These helpers aid in
reading and writing to/from the Bad Block Tables (BBTs) where the BBMs
are stored.

Signed-off-by: Lee Jones <lee.jones at linaro.org>
---
 drivers/mtd/nand/stm_nand_bch.c | 29 +++++++++++++++++++++++++++++
 1 file changed, 29 insertions(+)

diff --git a/drivers/mtd/nand/stm_nand_bch.c b/drivers/mtd/nand/stm_nand_bch.c
index 5bcaabbc..e1c71be 100644
--- a/drivers/mtd/nand/stm_nand_bch.c
+++ b/drivers/mtd/nand/stm_nand_bch.c
@@ -495,6 +495,35 @@ static uint8_t bch_write_page(struct nandi_controller *nandi,
 	return status;
 }
 
+/*
+ * Bad Block Tables/Bad Block Markers
+ */
+#define BBT_MARK_BAD_FACTORY	0x0
+#define BBT_MARK_BAD_WEAR	0x1
+#define BBT_MARK_GOOD		0x3
+
+static void bbt_set_block_mark(uint8_t *bbt, uint32_t block, uint8_t mark)
+{
+	unsigned int byte = block >> 2;
+	unsigned int shift = (block & 0x3) << 1;
+
+	bbt[byte] &= ~(0x3 << shift);
+	bbt[byte] |= ((mark & 0x3) << shift);
+}
+
+static uint8_t bbt_get_block_mark(uint8_t *bbt, uint32_t block)
+{
+	unsigned int byte = block >> 2;
+	unsigned int shift = (block & 0x3) << 1;
+
+	return (bbt[byte] >> shift) & 0x3;
+}
+
+static int bbt_is_block_bad(uint8_t *bbt, uint32_t block)
+{
+	return bbt_get_block_mark(bbt, block) == BBT_MARK_GOOD ? 0 : 1;
+}
+
 /* Scan block for IBBT signature */
 static int bch_find_ibbt_sig(struct nandi_controller *nandi,
 			     uint32_t block, int *bak, uint8_t *vers,
-- 
1.8.3.2