[POWERPC] Xilinx: of_serial support for Xilinx uart 16550.

The Xilinx 16550 uart core is not a standard 16550 because it uses
word-based addressing rather than byte-based addressing. With
additional properties it is compatible with the open firmware
'ns16550' compatible binding.

This code updates the of_serial driver to handle the reg-offset
and reg-shift properties to enable this core to be used.
Signed-off-by: John Linn <john.linn@xilinx.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Josh Boyer <jwboyer@linux.vnet.ibm.com>

Documentation/powerpc/booting-without-of.txt

@@ -2601,6 +2601,17 @@ platforms are moved over to use the flattened-device-tree model.
                       differ between different families.  May be
                       'virtex2p', 'virtex4', or 'virtex5'.
 
+      vi) Xilinx Uart 16550
+
+      Xilinx UART 16550 devices are very similar to the NS16550 but with
+      different register spacing and an offset from the base address.
+
+      Requred properties:
+       - clock-frequency : Frequency of the clock input
+       - reg-offset : A value of 3 is required
+       - reg-shift : A value of 2 is required
+
+
     p) Freescale Synchronous Serial Interface
 
        The SSI is a serial device that communicates with audio codecs.  It can

drivers/serial/of_serial.c

@@ -31,7 +31,8 @@ static int __devinit of_platform_serial_setup(struct of_device *ofdev,
 	struct resource resource;
 	struct device_node *np = ofdev->node;
 	const unsigned int *clk, *spd;
-	int ret;
+	const u32 *prop;
+	int ret, prop_size;
 
 	memset(port, 0, sizeof *port);
 	spd = of_get_property(np, "current-speed", NULL);
@@ -49,6 +50,17 @@ static int __devinit of_platform_serial_setup(struct of_device *ofdev,
 
 	spin_lock_init(&port->lock);
 	port->mapbase = resource.start;
+
+	/* Check for shifted address mapping */
+	prop = of_get_property(np, "reg-offset", &prop_size);
+	if (prop && (prop_size == sizeof(u32)))
+		port->mapbase += *prop;
+
+	/* Check for registers offset within the devices address range */
+	prop = of_get_property(np, "reg-shift", &prop_size);
+	if (prop && (prop_size == sizeof(u32)))
+		port->regshift = *prop;
+
 	port->irq = irq_of_parse_and_map(np, 0);
 	port->iotype = UPIO_MEM;
 	port->type = type;