nand: davinci: add support for 4K page size nand devices

It is needed for k2l keystone2 EVM which uses NAND flash with 4K page
size, hence add support for 4K page size nand devices.

[Brian: similar work submitted by Murali Karicheri <m-karicheri2@ti.com>
and Hao Zhang <hzhang@ti.com>]

Signed-off-by: Sandeep Paulraj <s-paulraj@ti.com>
Signed-off-by: Ivan Khoronzhuk <ivan.khoronzhuk@ti.com>
Signed-off-by: Brian Norris <computersforpeace@gmail.com>

drivers/mtd/nand/davinci_nand.c

@@ -520,6 +520,32 @@ static struct nand_ecclayout hwecc4_2048 = {
 	},
 };
 
+/*
+ * An ECC layout for using 4-bit ECC with large-page (4096bytes) flash,
+ * storing ten ECC bytes plus the manufacturer's bad block marker byte,
+ * and not overlapping the default BBT markers.
+ */
+static struct nand_ecclayout hwecc4_4096 = {
+	.eccbytes = 80,
+	.eccpos = {
+		/* at the end of spare sector */
+		48, 49, 50, 51, 52, 53, 54, 55, 56, 57,
+		58, 59, 60, 61, 62, 63, 64, 65, 66, 67,
+		68, 69, 70, 71, 72, 73, 74, 75, 76, 77,
+		78, 79, 80, 81, 82, 83, 84, 85, 86, 87,
+		88, 89, 90, 91, 92, 93, 94, 95, 96, 97,
+		98, 99, 100, 101, 102, 103, 104, 105, 106, 107,
+		108, 109, 110, 111, 112, 113, 114, 115, 116, 117,
+		118, 119, 120, 121, 122, 123, 124, 125, 126, 127,
+	},
+	.oobfree = {
+		/* 2 bytes at offset 0 hold manufacturer badblock markers */
+		{.offset = 2, .length = 46, },
+		/* 5 bytes at offset 8 hold BBT markers */
+		/* 8 bytes at offset 16 hold JFFS2 clean markers */
+	},
+};
+
 #if defined(CONFIG_OF)
 static const struct of_device_id davinci_nand_of_match[] = {
 	{.compatible = "ti,davinci-nand", },
@@ -796,18 +822,12 @@ static int nand_davinci_probe(struct platform_device *pdev)
 			info->chip.ecc.mode = NAND_ECC_HW_OOB_FIRST;
 			goto syndrome_done;
 		}
+		if (chunks == 8) {
+			info->ecclayout = hwecc4_4096;
+			info->chip.ecc.mode = NAND_ECC_HW_OOB_FIRST;
+			goto syndrome_done;
+		}
 
-		/* 4KiB page chips are not yet supported. The eccpos from
-		 * nand_ecclayout cannot hold 80 bytes and change to eccpos[]
-		 * breaks userspace ioctl interface with mtd-utils. Once we
-		 * resolve this issue, NAND_ECC_HW_OOB_FIRST mode can be used
-		 * for the 4KiB page chips.
-		 *
-		 * TODO: Note that nand_ecclayout has now been expanded and can
-		 *  hold plenty of OOB entries.
-		 */
-		dev_warn(&pdev->dev, "no 4-bit ECC support yet "
-				"for 4KiB-page NAND\n");
 		ret = -EIO;
 		goto err;