mtd: nand: kill the the NAND_MAX_PAGESIZE/NAND_MAX_OOBSIZE for nand_buffers{}

The patch converts the arrays to buffer pointers for nand_buffers{}.

The cafe_nand.c is the only NAND_OWN_BUFFERS user which allocates
nand_buffers{} itself.

This patch disables the DMA for nand_scan_ident, and restores the DMA
status after we finish the nand_scan_ident. This way, we can get page
size and OOB size and use them to allocate cafe->dmabuf.

Since the cafe_nand.c uses the NAND_ECC_HW_SYNDROME ECC mode, we do not
allocate the buffers for @ecccalc and @ecccode.

Signed-off-by: Huang Shijie <b32955@freescale.com>
Signed-off-by: Brian Norris <computersforpeace@gmail.com>
diff --git a/drivers/mtd/nand/nand_base.c b/drivers/mtd/nand/nand_base.c
index 9715a7b..deeaa1c 100644
--- a/drivers/mtd/nand/nand_base.c
+++ b/drivers/mtd/nand/nand_base.c
@@ -3696,15 +3696,26 @@
 	int i;
 	struct nand_chip *chip = mtd->priv;
 	struct nand_ecc_ctrl *ecc = &chip->ecc;
+	struct nand_buffers *nbuf;
 
 	/* New bad blocks should be marked in OOB, flash-based BBT, or both */
 	BUG_ON((chip->bbt_options & NAND_BBT_NO_OOB_BBM) &&
 			!(chip->bbt_options & NAND_BBT_USE_FLASH));
 
-	if (!(chip->options & NAND_OWN_BUFFERS))
-		chip->buffers = kmalloc(sizeof(*chip->buffers), GFP_KERNEL);
-	if (!chip->buffers)
-		return -ENOMEM;
+	if (!(chip->options & NAND_OWN_BUFFERS)) {
+		nbuf = kzalloc(sizeof(*nbuf) + mtd->writesize
+				+ mtd->oobsize * 3, GFP_KERNEL);
+		if (!nbuf)
+			return -ENOMEM;
+		nbuf->ecccalc = (uint8_t *)(nbuf + 1);
+		nbuf->ecccode = nbuf->ecccalc + mtd->oobsize;
+		nbuf->databuf = nbuf->ecccode + mtd->oobsize;
+
+		chip->buffers = nbuf;
+	} else {
+		if (!chip->buffers)
+			return -ENOMEM;
+	}
 
 	/* Set the internal oob buffer location, just after the page data */
 	chip->oob_poi = chip->buffers->databuf + mtd->writesize;