[PATCH v1] mtd: spinand: micron: correct parameters

[Martin Kurbanov]

This patch includes following fixes:
  1. Correct bitmask for ecc status. Valid bitmask is 0x70 in the
      status register.
  2. Fix oob layout:
        - The first 4 bytes are reserved for bad block data.
        - Use only non-protected ECC bytes for free data:
          OOB ECC protected Area is not used due to partial
          programming from some filesystems (like JFFS2 with
          cleanmarkers).

Signed-off-by: Martin Kurbanov <mmkurbanov at sberdevices.ru>
---
 drivers/mtd/nand/spi/micron.c | 28 ++++++++++++++++++++++++----
 1 file changed, 24 insertions(+), 4 deletions(-)

diff --git a/drivers/mtd/nand/spi/micron.c b/drivers/mtd/nand/spi/micron.c
index 50b7295bc922..897e70913ed0 100644
--- a/drivers/mtd/nand/spi/micron.c
+++ b/drivers/mtd/nand/spi/micron.c
@@ -12,7 +12,7 @@
 
 #define SPINAND_MFR_MICRON		0x2c
 
-#define MICRON_STATUS_ECC_MASK		GENMASK(7, 4)
+#define MICRON_STATUS_ECC_MASK		GENMASK(6, 4)
 #define MICRON_STATUS_ECC_NO_BITFLIPS	(0 << 4)
 #define MICRON_STATUS_ECC_1TO3_BITFLIPS	(1 << 4)
 #define MICRON_STATUS_ECC_4TO6_BITFLIPS	(3 << 4)
@@ -57,6 +57,20 @@ static SPINAND_OP_VARIANTS(x1_write_cache_variants,
 static SPINAND_OP_VARIANTS(x1_update_cache_variants,
 			   SPINAND_PROG_LOAD(false, 0, NULL, 0));
 
+/*
+ * OOB spare area map (128 and 256 bytes)
+ *
+ *           +-----+-----------------+-------------------+---------------------+
+ *           | BBM |     Non ECC     |   ECC protected   |      ECC Area       |
+ *           |     | protected Area  |       Area        |                     |
+ * ----------+-----+-----------------+-------------------+---------------------+
+ *  oobsize  | 0:3 | 4:31 (28 bytes) | 32:63 (32 bytes)  | 64:127 (64 bytes)   |
+ * 128 bytes |     |                 |                   |                     |
+ * ----------+-----+-----------------+-------------------+---------------------+
+ *  oobsize  | 0:3 | 4:63 (60 bytes) | 64:127 (64 bytes) | 127:255 (128 bytes) |
+ * 256 bytes |     |                 |                   |                     |
+ * ----------+-----+-----------------+-------------------+---------------------+
+ */
 static int micron_8_ooblayout_ecc(struct mtd_info *mtd, int section,
 				  struct mtd_oob_region *region)
 {
@@ -75,9 +89,15 @@ static int micron_8_ooblayout_free(struct mtd_info *mtd, int section,
 	if (section)
 		return -ERANGE;
 
-	/* Reserve 2 bytes for the BBM. */
-	region->offset = 2;
-	region->length = (mtd->oobsize / 2) - 2;
+	/* Reserve 4 bytes for the BBM. */
+	region->offset = 4;
+
+	/* The OOB Free (User) area is divided into two equal parts:
+	 *   the first part is not protected by ECC;
+	 *   the second part is protected by ECC.
+	 * Use only non-protected ECC bytes.
+	 */
+	region->length = (mtd->oobsize / 2) / 2 - 4;
 
 	return 0;
 }
-- 
2.40.0