ARM: OMAP2+: Allow NAND transfer mode to be specified in DT

OMAP devices support various NAND transfer modes.

Currently all device-tree definitions will use the default "prefetch
polled" mode, so this patch enables the transfer mode to be specified
in the device-tree.
Signed-off-by: Mark Jackson <mpfj@newflow.co.uk>
Acked-by: Pekon Gupta <pekon@ti.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>

Documentation/devicetree/bindings/mtd/gpmc-nand.txt

@@ -29,6 +29,13 @@ Optional properties:
 		"bch4"		4-bit BCH ecc code
 		"bch8"		8-bit BCH ecc code
 
+ - ti,nand-xfer-type:		A string setting the data transfer type. One of:
+
+		"prefetch-polled"	Prefetch polled mode (default)
+		"polled"		Polled mode, without prefetch
+		"prefetch-dma"		Prefetch enabled sDMA mode
+		"prefetch-irq"		Prefetch enabled irq mode
+
  - elm_id:	Specifies elm device node. This is required to support BCH
  		error correction using ELM module.
 
@@ -55,6 +62,7 @@ Example for an AM33xx board:
 			reg = <0 0 0>; /* CS0, offset 0 */
 			nand-bus-width = <16>;
 			ti,nand-ecc-opt = "bch8";
+			ti,nand-xfer-type = "polled";
 
 			gpmc,sync-clk-ps = <0>;
 			gpmc,cs-on-ns = <0>;

arch/arm/mach-omap2/gpmc.c

@@ -1345,6 +1345,13 @@ static const char * const nand_ecc_opts[] = {
 	[OMAP_ECC_BCH8_CODE_HW]			= "bch8",
 };
 
+static const char * const nand_xfer_types[] = {
+	[NAND_OMAP_PREFETCH_POLLED]		= "prefetch-polled",
+	[NAND_OMAP_POLLED]			= "polled",
+	[NAND_OMAP_PREFETCH_DMA]		= "prefetch-dma",
+	[NAND_OMAP_PREFETCH_IRQ]		= "prefetch-irq",
+};
+
 static int gpmc_probe_nand_child(struct platform_device *pdev,
 				 struct device_node *child)
 {
@@ -1374,6 +1381,13 @@ static int gpmc_probe_nand_child(struct platform_device *pdev,
 				break;
 			}
 
+	if (!of_property_read_string(child, "ti,nand-xfer-type", &s))
+		for (val = 0; val < ARRAY_SIZE(nand_xfer_types); val++)
+			if (!strcasecmp(s, nand_xfer_types[val])) {
+				gpmc_nand_data->xfer_type = val;
+				break;
+			}
+
 	val = of_get_nand_bus_width(child);
 	if (val == 16)
 		gpmc_nand_data->devsize = NAND_BUSWIDTH_16;