[RFC PATCH] mtd: mxc_nand: fix OOB corruption when page size > 2k

[Baruch Siach]

When page size is 4k, ecc.total is set to 8*9, and this causes
nand_write_page_hwecc() to read past the initialized part of the eccpos array,
which corrupts chip->oob_poi with bogus values from ecc_calc.

Fix this by creating a proper nand_ecclayout for 4k flashes.

Signed-off-by: Baruch Siach <baruch at tkos.co.il>
---

I'm not sure if this is the right fix. The proposed nandv2_hw_eccoob_4k is just 
a natural extension of nandv2_hw_eccoob_largepage. However, I'm not convinced 
that this actually matches the hardware behaviour. Anyway, this fixed a real 
OOB corruption in BBT, which is the only place I know of where the OOB area is 
actually used.

Comments are welcome.

 drivers/mtd/nand/mxc_nand.c |   27 +++++++++++++++++++++++++++
 1 files changed, 27 insertions(+), 0 deletions(-)

diff --git a/drivers/mtd/nand/mxc_nand.c b/drivers/mtd/nand/mxc_nand.c
index ef932ba..0fc80db 100644
--- a/drivers/mtd/nand/mxc_nand.c
+++ b/drivers/mtd/nand/mxc_nand.c
@@ -211,6 +211,31 @@ static struct nand_ecclayout nandv2_hw_eccoob_largepage = {
 	}
 };
 
+/* OOB description for 4096 byte pages with 128 byte OOB */
+static struct nand_ecclayout nandv2_hw_eccoob_4k = {
+	.eccbytes = 8 * 9,
+	.eccpos = {
+		7,  8,  9, 10, 11, 12, 13, 14, 15,
+		23, 24, 25, 26, 27, 28, 29, 30, 31,
+		39, 40, 41, 42, 43, 44, 45, 46, 47,
+		55, 56, 57, 58, 59, 60, 61, 62, 63,
+		71, 72, 73, 74, 75, 76, 77, 78, 79,
+		87, 88, 89, 90, 91, 92, 93, 94, 95,
+		103, 104, 105, 106, 107, 108, 109, 110, 111,
+		119, 120, 121, 122, 123, 124, 125, 126, 127,
+	},
+	.oobfree = {
+		{.offset = 2, .length = 4},
+		{.offset = 16, .length = 7},
+		{.offset = 32, .length = 7},
+		{.offset = 48, .length = 7},
+		{.offset = 64, .length = 7},
+		{.offset = 80, .length = 7},
+		{.offset = 96, .length = 7},
+		{.offset = 112, .length = 7},
+	}
+};
+
 #ifdef CONFIG_MTD_PARTITIONS
 static const char *part_probes[] = { "RedBoot", "cmdlinepart", NULL };
 #endif
@@ -1186,6 +1211,8 @@ static int __init mxcnd_probe(struct platform_device *pdev)
 
 	if (mtd->writesize == 2048)
 		this->ecc.layout = oob_largepage;
+	if (nfc_is_v21() && mtd->writesize == 4096)
+		this->ecc.layout = &nandv2_hw_eccoob_4k;
 
 	/* second phase scan */
 	if (nand_scan_tail(mtd)) {
-- 
1.7.2.3