[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>

2 files changed, 102 insertions, 0 deletions

diff --git a/drivers/serial/samsung.c b/drivers/serial/samsung.c
index 1e219d3d0352..ebeda832c8a3 100644
--- a/drivers/serial/samsung.c
+++ b/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);
         }
diff --git a/drivers/serial/samsung.h b/drivers/serial/samsung.h
index 5c92ebbe7d9e..be263423205d 100644
--- a/drivers/serial/samsung.h
+++ b/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 */