tty: of_serial: support for 32 bit accesses

Some platforms e.g. TI Davinci require 32-bit accesses to the UARTs.
The of_serial driver currently registers all UARTs as UPIO_MEM.  Add a
new attribute "reg-io-width" to allow the port to be registered with
different IO width requirements.
Acked-by: NAlan Cox <alan@linux.intel.com>
Signed-off-by: NJamie Iles <jamie@jamieiles.com>
Signed-off-by: NGrant Likely <grant.likely@secretlab.ca>

Documentation/devicetree/bindings/tty/serial/of-serial.txt

@@ -19,6 +19,9 @@ Optional properties:
 - current-speed : the current active speed of the UART.
 - reg-offset : offset to apply to the mapbase from the start of the registers.
 - reg-shift : quantity to shift the register offsets by.
+- reg-io-width : the size (in bytes) of the IO accesses that should be
+  performed on the device.  There are some systems that require 32-bit
+  accesses to the UART (e.g. TI davinci).
 - used-by-rtas : set to indicate that the port is in use by the OpenFirmware
   RTAS and should not be registered.
 

drivers/tty/serial/of_serial.c

@@ -65,6 +65,23 @@ static int __devinit of_platform_serial_setup(struct platform_device *ofdev,
 
 	port->irq = irq_of_parse_and_map(np, 0);
 	port->iotype = UPIO_MEM;
+	prop = of_get_property(np, "reg-io-width", &prop_size);
+	if (prop && (prop_size == sizeof(u32))) {
+		switch (be32_to_cpup(prop)) {
+		case 1:
+			port->iotype = UPIO_MEM;
+			break;
+		case 4:
+			port->iotype = UPIO_MEM32;
+			break;
+		default:
+			dev_warn(&ofdev->dev,
+				 "unsupported io width (%d bytes)\n",
+				 be32_to_cpup(prop));
+			return -EINVAL;
+		}
+	}
+
 	port->type = type;
 	port->uartclk = be32_to_cpup(clk);
 	port->flags = UPF_SHARE_IRQ | UPF_BOOT_AUTOCONF | UPF_IOREMAP