tty: serial: altera_uart: Add devicetree support

With the recent switch of the (currently still out-of-tree) Nios2 Linux
port to devicetree we want to be able to retrieve the resources and
properties from dts.

The old method to retrieve resources and properties from platform data
is still supported.

Signed-off-by: Tobias Klauser <[e-mail]>
Acked-by: Greg Kroah-Hartman <[e-mail]>
Signed-off-by: Grant Likely <[e-mail]>

Documentation/devicetree/bindings/serial/altera_uart.txt

···
+Altera UART
+
+Required properties:
+- compatible : should be "ALTR,uart-1.0"
+
+Optional properties:
+- clock-frequency : frequency of the clock input to the UART

drivers/tty/serial/altera_uart.c

···
 #include <linux/serial.h>
 #include <linux/serial_core.h>
 #include <linux/platform_device.h>
+#include <linux/of.h>
 #include <linux/io.h>
 #include <linux/altera_uart.h>
 
···
 	.cons		= ALTERA_UART_CONSOLE,
 };
 
+#ifdef CONFIG_OF
+static int altera_uart_get_of_uartclk(struct platform_device *pdev,
+				      struct uart_port *port)
+{
+	int len;
+	const __be32 *clk;
+
+	clk = of_get_property(pdev->dev.of_node, "clock-frequency", &len);
+	if (!clk || len < sizeof(__be32))
+		return -ENODEV;
+
+	port->uartclk = be32_to_cpup(clk);
+
+	return 0;
+}
+#else
+static int altera_uart_get_of_uartclk(struct platform_device *pdev,
+				      struct uart_port *port)
+{
+	return -ENODEV;
+}
+#endif /* CONFIG_OF */
+
 static int __devinit altera_uart_probe(struct platform_device *pdev)
 {
 	struct altera_uart_platform_uart *platp = pdev->dev.platform_data;
···
 	struct resource *res_mem;
 	struct resource *res_irq;
 	int i = pdev->id;
+	int ret;
 
 	/* -1 emphasizes that the platform must have one port, no .N suffix */
 	if (i == -1)
···
 	else if (platp->irq)
 		port->irq = platp->irq;
 
+	/* Check platform data first so we can override device node data */
+	if (platp)
+		port->uartclk = platp->uartclk;
+	else {
+		ret = altera_uart_get_of_uartclk(pdev, port);
+		if (ret)
+			return ret;
+	}
+
 	port->membase = ioremap(port->mapbase, ALTERA_UART_SIZE);
 	if (!port->membase)
 		return -ENOMEM;
···
 	port->line = i;
 	port->type = PORT_ALTERA_UART;
 	port->iotype = SERIAL_IO_MEM;
-	port->uartclk = platp->uartclk;
 	port->ops = &altera_uart_ops;
 	port->flags = UPF_BOOT_AUTOCONF;
 	port->private_data = platp;
···
 	return 0;
 }
 
+#ifdef CONFIG_OF
+static struct of_device_id altera_uart_match[] = {
+	{ .compatible = "ALTR,uart-1.0", },
+	{},
+};
+MODULE_DEVICE_TABLE(of, altera_uart_match);
+#else
+#define altera_uart_match NULL
+#endif /* CONFIG_OF */
+
 static struct platform_driver altera_uart_platform_driver = {
 	.probe	= altera_uart_probe,
 	.remove	= __devexit_p(altera_uart_remove),
 	.driver	= {
-		.name	= DRV_NAME,
-		.owner	= THIS_MODULE,
-		.pm	= NULL,
+		.name		= DRV_NAME,
+		.owner		= THIS_MODULE,
+		.of_match_table	= altera_uart_match,
 	},
 };