[PATCH v2 1/3] mtd: nand: omap: fix ecclayout->oobfree->offset

[Pekon Gupta]

1) In current implementation, ecclayout->oobfree->offset is calculated with
 respect to ecclayout->eccpos[0] which is incorrect because ECC bytes may not
 be stored contiguously in OOB.
 So, this patch calculates ecclayout->oobfree->offset with respect to last
 ECC byte-position 'eccpos[ecclayout->eccbytes-1]'.

2) ECC layout of some ecc-schemes expects reserved-markers at specific eccpos[]
 which should not be over-written by any file-system metadata.
 So this patch aligns oobfree->offset taking into account of such markers.

Tested-by: Enric Balletbo i Serra <eballetbo at gmail.com>
Tested-by: Stefan Roese <sr at denx.de>
Signed-off-by: Pekon Gupta <pekon at ti.com>
---
 drivers/mtd/nand/omap2.c | 25 +++++++++++++++----------
 1 file changed, 15 insertions(+), 10 deletions(-)

diff --git a/drivers/mtd/nand/omap2.c b/drivers/mtd/nand/omap2.c
index ef4190a..874fd9d 100644
--- a/drivers/mtd/nand/omap2.c
+++ b/drivers/mtd/nand/omap2.c
@@ -1829,8 +1829,9 @@ static int omap_nand_probe(struct platform_device *pdev)
 			ecclayout->eccpos[0]	= BADBLOCK_MARKER_LENGTH;
 		else
 			ecclayout->eccpos[0]	= 1;
-		ecclayout->oobfree->offset	= ecclayout->eccpos[0] +
-							ecclayout->eccbytes;
+		/* no reserved-marker in ecclayout for this ecc-scheme */
+		ecclayout->oobfree->offset	=
+				ecclayout->eccpos[ecclayout->eccbytes - 1] + 1;
 		break;
 
 	case OMAP_ECC_BCH4_CODE_HW_DETECTION_SW:
@@ -1848,8 +1849,9 @@ static int omap_nand_probe(struct platform_device *pdev)
 							(mtd->writesize /
 							nand_chip->ecc.size);
 		ecclayout->eccpos[0]		= BADBLOCK_MARKER_LENGTH;
-		ecclayout->oobfree->offset	= ecclayout->eccpos[0] +
-							ecclayout->eccbytes;
+		/* include reserved-marker in ecclayout->oobfree calculation */
+		ecclayout->oobfree->offset	= 1 +
+				ecclayout->eccpos[ecclayout->eccbytes - 1] + 1;
 		/* software bch library is used for locating errors */
 		nand_chip->ecc.priv		= nand_bch_init(mtd,
 							nand_chip->ecc.size,
@@ -1884,8 +1886,9 @@ static int omap_nand_probe(struct platform_device *pdev)
 							(mtd->writesize /
 							nand_chip->ecc.size);
 		ecclayout->eccpos[0]		= BADBLOCK_MARKER_LENGTH;
-		ecclayout->oobfree->offset	= ecclayout->eccpos[0] +
-							ecclayout->eccbytes;
+		/* reserved marker already included in ecclayout->eccbytes */
+		ecclayout->oobfree->offset	=
+				ecclayout->eccpos[ecclayout->eccbytes - 1] + 1;
 		/* This ECC scheme requires ELM H/W block */
 		if (is_elm_present(info, pdata->elm_of_node, BCH4_ECC) < 0) {
 			pr_err("nand: error: could not initialize ELM\n");
@@ -1914,8 +1917,9 @@ static int omap_nand_probe(struct platform_device *pdev)
 							(mtd->writesize /
 							nand_chip->ecc.size);
 		ecclayout->eccpos[0]		= BADBLOCK_MARKER_LENGTH;
-		ecclayout->oobfree->offset	= ecclayout->eccpos[0] +
-							ecclayout->eccbytes;
+		/* include reserved-marker in ecclayout->oobfree calculation */
+		ecclayout->oobfree->offset	= 1 +
+				ecclayout->eccpos[ecclayout->eccbytes - 1] + 1;
 		/* software bch library is used for locating errors */
 		nand_chip->ecc.priv		= nand_bch_init(mtd,
 							nand_chip->ecc.size,
@@ -1957,8 +1961,9 @@ static int omap_nand_probe(struct platform_device *pdev)
 							(mtd->writesize /
 							nand_chip->ecc.size);
 		ecclayout->eccpos[0]		= BADBLOCK_MARKER_LENGTH;
-		ecclayout->oobfree->offset	= ecclayout->eccpos[0] +
-							ecclayout->eccbytes;
+		/* reserved marker already included in ecclayout->eccbytes */
+		ecclayout->oobfree->offset	=
+				ecclayout->eccpos[ecclayout->eccbytes - 1] + 1;
 		break;
 #else
 		pr_err("nand: error: CONFIG_MTD_NAND_OMAP_BCH not enabled\n");
-- 
1.8.5.1.163.gd7aced9