serial: xilinx_uartps: Get clock rate info from dts

Add support for specifying clock information for the uart clk via the
device tree. This eliminates the need to hardcode rates in the device
tree.

Signed-off-by: Josh Cartwright <[e-mail]>
Signed-off-by: Wei Yongjun <[e-mail]>
Acked-by: Michal Simek <[e-mail]>
Acked-by: Arnd Bergmann <[e-mail]>
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

arch/arm/boot/dts/zynq-7000.dtsi

···
 			compatible = "xlnx,xuartps";
 			reg = <0xE0000000 0x1000>;
 			interrupts = <0 27 4>;
-			clock = <50000000>;
+			clocks = <&uart_clk 0>;
 		};
 
 		uart1: uart@e0001000 {
 			compatible = "xlnx,xuartps";
 			reg = <0xE0001000 0x1000>;
 			interrupts = <0 50 4>;
-			clock = <50000000>;
+			clocks = <&uart_clk 1>;
 		};
 
 		slcr: slcr@f8000000 {

drivers/tty/serial/xilinx_uartps.c

···
 #include <linux/tty.h>
 #include <linux/tty_flip.h>
 #include <linux/console.h>
+#include <linux/clk.h>
 #include <linux/irq.h>
 #include <linux/io.h>
 #include <linux/of.h>
···
 	int rc;
 	struct uart_port *port;
 	struct resource *res, *res2;
-	int clk = 0;
+	struct clk *clk;
 
-	const unsigned int *prop;
-
-	prop = of_get_property(pdev->dev.of_node, "clock", NULL);
-	if (prop)
-		clk = be32_to_cpup(prop);
-	if (!clk) {
+	clk = of_clk_get(pdev->dev.of_node, 0);
+	if (IS_ERR(clk)) {
 		dev_err(&pdev->dev, "no clock specified\n");
-		return -ENODEV;
+		return PTR_ERR(clk);
+	}
+
+	rc = clk_prepare_enable(clk);
+	if (rc) {
+		dev_err(&pdev->dev, "could not enable clock\n");
+		return -EBUSY;
 	}
 
 	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
···
 		port->mapbase = res->start;
 		port->irq = res2->start;
 		port->dev = &pdev->dev;
-		port->uartclk = clk;
+		port->uartclk = clk_get_rate(clk);
+		port->private_data = clk;
 		dev_set_drvdata(&pdev->dev, port);
 		rc = uart_add_one_port(&xuartps_uart_driver, port);
 		if (rc) {
···
 static int xuartps_remove(struct platform_device *pdev)
 {
 	struct uart_port *port = dev_get_drvdata(&pdev->dev);
-	int rc = 0;
+	struct clk *clk = port->private_data;
+	int rc;
 
 	/* Remove the xuartps port from the serial core */
-	if (port) {
-		rc = uart_remove_one_port(&xuartps_uart_driver, port);
-		dev_set_drvdata(&pdev->dev, NULL);
-		port->mapbase = 0;
-	}
+	rc = uart_remove_one_port(&xuartps_uart_driver, port);
+	dev_set_drvdata(&pdev->dev, NULL);
+	port->mapbase = 0;
+	clk_disable_unprepare(clk);
 	return rc;
 }