[ARM] CPUFREQ: S3C24XX serial CPU frequency scaling support.

Add support for CPU frequency scalling to the S3C24XX serial
driver.
Signed-off-by: Ben Dooks <ben-linux@fluff.org>

drivers/serial/samsung.c

@@ -42,6 +42,7 @@
 #include <linux/serial.h>
 #include <linux/delay.h>
 #include <linux/clk.h>
+#include <linux/cpufreq.h>
 
 #include <asm/irq.h>
 
@@ -452,6 +453,8 @@ static void s3c24xx_serial_pm(struct uart_port *port, unsigned int level,
 {
 	struct s3c24xx_uart_port *ourport = to_ourport(port);
 
+	ourport->pm_level = level;
+
 	switch (level) {
 	case 3:
 		if (!IS_ERR(ourport->baudclk) && ourport->baudclk != NULL)
@@ -661,6 +664,7 @@ static void s3c24xx_serial_set_termios(struct uart_port *port,
 
 		ourport->clksrc = clksrc;
 		ourport->baudclk = clk;
+		ourport->baudclk_rate = clk ? clk_get_rate(clk) : 0;
 	}
 
 	switch (termios->c_cflag & CSIZE) {
@@ -890,6 +894,93 @@ static inline int s3c24xx_serial_resetport(struct uart_port *port,
 	return (info->reset_port)(port, cfg);
 }
 
+
+#ifdef CONFIG_CPU_FREQ
+
+static int s3c24xx_serial_cpufreq_transition(struct notifier_block *nb,
+					     unsigned long val, void *data)
+{
+	struct s3c24xx_uart_port *port;
+	struct uart_port *uport;
+
+	port = container_of(nb, struct s3c24xx_uart_port, freq_transition);
+	uport = &port->port;
+
+	/* check to see if port is enabled */
+
+	if (port->pm_level != 0)
+		return 0;
+
+	/* try and work out if the baudrate is changing, we can detect
+	 * a change in rate, but we do not have support for detecting
+	 * a disturbance in the clock-rate over the change.
+	 */
+
+	if (IS_ERR(port->clk))
+		goto exit;
+
+	if (port->baudclk_rate == clk_get_rate(port->clk))
+		goto exit;
+
+	if (val == CPUFREQ_PRECHANGE) {
+		/* we should really shut the port down whilst the
+		 * frequency change is in progress. */
+
+	} else if (val == CPUFREQ_POSTCHANGE) {
+		struct ktermios *termios;
+		struct tty_struct *tty;
+
+		if (uport->info == NULL) {
+			printk(KERN_WARNING "%s: info NULL\n", __func__);
+			goto exit;
+		}
+
+		tty = uport->info->port.tty;
+
+		if (tty == NULL) {
+			printk(KERN_WARNING "%s: tty is NULL\n", __func__);
+			goto exit;
+		}
+
+		termios = tty->termios;
+
+		if (termios == NULL) {
+			printk(KERN_WARNING "%s: no termios?\n", __func__);
+			goto exit;
+		}
+
+		s3c24xx_serial_set_termios(uport, termios, NULL);
+	}
+
+ exit:
+	return 0;
+}
+
+static inline int s3c24xx_serial_cpufreq_register(struct s3c24xx_uart_port *port)
+{
+	port->freq_transition.notifier_call = s3c24xx_serial_cpufreq_transition;
+
+	return cpufreq_register_notifier(&port->freq_transition,
+					 CPUFREQ_TRANSITION_NOTIFIER);
+}
+
+static inline void s3c24xx_serial_cpufreq_deregister(struct s3c24xx_uart_port *port)
+{
+	cpufreq_unregister_notifier(&port->freq_transition,
+				    CPUFREQ_TRANSITION_NOTIFIER);
+}
+
+#else
+static inline int s3c24xx_serial_cpufreq_register(struct s3c24xx_uart_port *port)
+{
+	return 0;
+}
+
+static inline void s3c24xx_serial_cpufreq_deregister(struct s3c24xx_uart_port *port)
+{
+}
+#endif
+
 /* s3c24xx_serial_init_port
  *
  * initialise a single serial port from the platform device given
@@ -1002,6 +1093,10 @@ int s3c24xx_serial_probe(struct platform_device *dev,
 	if (ret < 0)
 		printk(KERN_ERR "%s: failed to add clksrc attr.\n", __func__);
 
+	ret = s3c24xx_serial_cpufreq_register(ourport);
+	if (ret < 0)
+		dev_err(&dev->dev, "failed to add cpufreq notifier\n");
+
 	return 0;
 
  probe_err:
@@ -1015,6 +1110,7 @@ int s3c24xx_serial_remove(struct platform_device *dev)
 	struct uart_port *port = s3c24xx_dev_to_port(&dev->dev);
 
 	if (port) {
+		s3c24xx_serial_cpufreq_deregister(to_ourport(port));
 		device_remove_file(&dev->dev, &dev_attr_clock_source);
 		uart_remove_one_port(&s3c24xx_uart_drv, port);
 	}

drivers/serial/samsung.h

@@ -33,12 +33,18 @@ struct s3c24xx_uart_info {
 struct s3c24xx_uart_port {
 	unsigned char			rx_claimed;
 	unsigned char			tx_claimed;
+	unsigned int			pm_level;
+	unsigned long			baudclk_rate;
 
 	struct s3c24xx_uart_info	*info;
 	struct s3c24xx_uart_clksrc	*clksrc;
 	struct clk			*clk;
 	struct clk			*baudclk;
 	struct uart_port		port;
+
+#ifdef CONFIG_CPU_FREQ
+	struct notifier_block		freq_transition;
+#endif
 };
 
 /* conversion functions */