mtd: nand: extend NAND flash detection to new MLC chips

Some of the newer MLC devices have a 6-byte ID sequence in which
several field definitions differ from older chips in a manner that is
not backward compatible.  For instance:

Samsung K9GAG08U0M (5-byte sequence): ec d5 14 b6 74
4th byte, bits 1:0 encode the page size: 0=1KiB, 1=2KiB, 2=4KiB, 3=8KiB
4th byte, bits 5:4 encode the block size: 0=64KiB, 1=128KiB, ...
4th byte, bit 6 encodes the OOB size: 0=8B/512B, 1=16B/512B

Samsung K9GAG08U0D (6-byte sequence): ec d5 94 29 34 41
4th byte, bits 1:0 encode the page size: 0=2KiB, 1=4KiB, 3=8KiB, 4=rsvd
4th byte, bits 7;5:4 encode the block size: 0=128KiB, 1=256KiB, ...
4th byte, bits 6;3:2 encode the OOB size: 1=128B/page, 2=218B/page

This patch uses the new 6-byte scheme if the following conditions are
all true:

1) The ID code wraps around after exactly 6 bytes

2) Manufacturer is Samsung

3) 6th byte is zero

The patch also extends the maximum OOB size from 128B to 256B.
Signed-off-by: Kevin Cernekee <cernekee@gmail.com>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>

drivers/mtd/nand/nand_base.c

@@ -2774,8 +2774,8 @@ static struct nand_flash_dev *nand_get_flash_type(struct mtd_info *mtd,
 						  int busw, int *maf_id,
 						  struct nand_flash_dev *type)
 {
-	int dev_id, maf_idx;
-	int tmp_id, tmp_manf;
+	int i, dev_id, maf_idx;
+	u8 id_data[8];
 
 	/* Select the device */
 	chip->select_chip(mtd, 0);
@@ -2801,15 +2801,15 @@ static struct nand_flash_dev *nand_get_flash_type(struct mtd_info *mtd,
 
 	chip->cmdfunc(mtd, NAND_CMD_READID, 0x00, -1);
 
-	/* Read manufacturer and device IDs */
+	/* Read entire ID string */
 
-	tmp_manf = chip->read_byte(mtd);
-	tmp_id = chip->read_byte(mtd);
+	for (i = 0; i < 8; i++)
+		id_data[i] = chip->read_byte(mtd);
 
-	if (tmp_manf != *maf_id || tmp_id != dev_id) {
+	if (id_data[0] != *maf_id || id_data[1] != dev_id) {
 		printk(KERN_INFO "%s: second ID read did not match "
 		       "%02x,%02x against %02x,%02x\n", __func__,
-		       *maf_id, dev_id, tmp_manf, tmp_id);
+		       *maf_id, dev_id, id_data[0], id_data[1]);
 		return ERR_PTR(-ENODEV);
 	}
 
@@ -2832,21 +2832,45 @@ static struct nand_flash_dev *nand_get_flash_type(struct mtd_info *mtd,
 	if (!type->pagesize) {
 		int extid;
 		/* The 3rd id byte holds MLC / multichip data */
-		chip->cellinfo = chip->read_byte(mtd);
+		chip->cellinfo = id_data[2];
 		/* The 4th id byte is the important one */
-		extid = chip->read_byte(mtd);
+		extid = id_data[3];
+
+		/*
+		 * Field definitions are in the following datasheets:
+		 * Old style (4,5 byte ID): Samsung K9GAG08U0M (p.32)
+		 * New style   (6 byte ID): Samsung K9GAG08U0D (p.40)
+		 *
+		 * Check for wraparound + Samsung ID + nonzero 6th byte
+		 * to decide what to do.
+		 */
+		if (id_data[0] == id_data[6] && id_data[1] == id_data[7] &&
+				id_data[0] == NAND_MFR_SAMSUNG &&
+				id_data[5] != 0x00) {
+			/* Calc pagesize */
+			mtd->writesize = 2048 << (extid & 0x03);
+			extid >>= 2;
+			/* Calc oobsize */
+			mtd->oobsize = (extid & 0x03) == 0x01 ? 128 : 218;
+			extid >>= 2;
+			/* Calc blocksize */
+			mtd->erasesize = (128 * 1024) <<
+				(((extid >> 1) & 0x04) | (extid & 0x03));
+			busw = 0;
+		} else {
 			/* Calc pagesize */
-		mtd->writesize = 1024 << (extid & 0x3);
+			mtd->writesize = 1024 << (extid & 0x03);
 			extid >>= 2;
 			/* Calc oobsize */
-		mtd->oobsize = (8 << (extid & 0x01)) * (mtd->writesize >> 9);
+			mtd->oobsize = (8 << (extid & 0x01)) *
+				(mtd->writesize >> 9);
 			extid >>= 2;
 			/* Calc blocksize. Blocksize is multiples of 64KiB */
 			mtd->erasesize = (64 * 1024) << (extid & 0x03);
 			extid >>= 2;
 			/* Get buswidth information */
 			busw = (extid & 0x01) ? NAND_BUSWIDTH_16 : 0;
-
+		}
 	} else {
 		/*
 		 * Old devices have chip data hardcoded in the device id table

include/linux/mtd/nand.h

@@ -53,7 +53,7 @@ extern int nand_unlock(struct mtd_info *mtd, loff_t ofs, uint64_t len);
  * is supported now. If you add a chip with bigger oobsize/page
  * adjust this accordingly.
  */
-#define NAND_MAX_OOBSIZE	128
+#define NAND_MAX_OOBSIZE	256
 #define NAND_MAX_PAGESIZE	4096
 
 /*