ARM: davinci: serial: provide API to initialze UART clocks

Provide an API to initialize a UART clock. Refactor existing
davinci_serial_init() to separate out the part which enables
the clock.

This will later be used to help DA850 DT boot support.
Signed-off-by: Sekhar Nori <nsekhar@ti.com>

arch/arm/mach-davinci/include/mach/serial.h

@@ -43,6 +43,7 @@ struct davinci_uart_config {
 };
 
 extern int davinci_serial_init(struct davinci_uart_config *);
+extern int davinci_serial_setup_clk(unsigned instance, unsigned int *rate);
 #endif
 
 #endif /* __ASM_ARCH_SERIAL_H */

arch/arm/mach-davinci/serial.c

@@ -70,11 +70,33 @@ static void __init davinci_serial_reset(struct plat_serial8250_port *p)
 				 UART_DM646X_SCR_TX_WATERMARK);
 }
 
-int __init davinci_serial_init(struct davinci_uart_config *info)
+/* Enable UART clock and obtain its rate */
+int __init davinci_serial_setup_clk(unsigned instance, unsigned int *rate)
 {
-	int i;
 	char name[16];
-	struct clk *uart_clk;
+	struct clk *clk;
+	struct davinci_soc_info *soc_info = &davinci_soc_info;
+	struct device *dev = &soc_info->serial_dev->dev;
+
+	sprintf(name, "uart%d", instance);
+	clk = clk_get(dev, name);
+	if (IS_ERR(clk)) {
+		pr_err("%s:%d: failed to get UART%d clock\n",
+					__func__, __LINE__, instance);
+		return PTR_ERR(clk);
+	}
+
+	clk_prepare_enable(clk);
+
+	if (rate)
+		*rate = clk_get_rate(clk);
+
+	return 0;
+}
+
+int __init davinci_serial_init(struct davinci_uart_config *info)
+{
+	int i, ret;
 	struct davinci_soc_info *soc_info = &davinci_soc_info;
 	struct device *dev = &soc_info->serial_dev->dev;
 	struct plat_serial8250_port *p = dev->platform_data;
@@ -87,16 +109,9 @@ int __init davinci_serial_init(struct davinci_uart_config *info)
 		if (!(info->enabled_uarts & (1 << i)))
 			continue;
 
-		sprintf(name, "uart%d", i);
-		uart_clk = clk_get(dev, name);
-		if (IS_ERR(uart_clk)) {
-			printk(KERN_ERR "%s:%d: failed to get UART%d clock\n",
-					__func__, __LINE__, i);
+		ret = davinci_serial_setup_clk(i, &p->uartclk);
+		if (ret)
 			continue;
-		}
-
-		clk_prepare_enable(uart_clk);
-		p->uartclk = clk_get_rate(uart_clk);
 
 		if (!p->membase && p->mapbase) {
 			p->membase = ioremap(p->mapbase, SZ_4K);