[PATCH] RTC subsystem: DS1672 oscillator handling

* Always enable the oscillator when we set the time
* If the oscillator is disable when we probe the RTC report back a warning
  to the user
* Added sysfs attribute to represent the state of the oscillator

Signed-off-by: Kumar Gala <galak@kernel.crashing.org>
Signed-off-by: Alessandro Zummo <a.zummo@towertech.it>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 58 insertions, 3 deletions

diff --git a/drivers/rtc/rtc-ds1672.c b/drivers/rtc/rtc-ds1672.c
index 358695a416f3..6d2dc7060652 100644
--- a/drivers/rtc/rtc-ds1672.c
+++ b/drivers/rtc/rtc-ds1672.c
@@ -23,6 +23,7 @@ I2C_CLIENT_INSMOD;
 
 #define DS1672_REG_CNT_BASE     0
 #define DS1672_REG_CONTROL      4
+#define DS1672_REG_CONTROL_EOSC 0x80
 #define DS1672_REG_TRICKLE      5
 
 
@@ -72,16 +73,17 @@ static int ds1672_get_datetime(struct i2c_client *client, struct rtc_time *tm)
 static int ds1672_set_mmss(struct i2c_client *client, unsigned long secs)
 {
         int xfer;
-        unsigned char buf[5];
+        unsigned char buf[6];
 
         buf[0] = DS1672_REG_CNT_BASE;
         buf[1] = secs & 0x000000FF;
         buf[2] = (secs & 0x0000FF00) >> 8;
         buf[3] = (secs & 0x00FF0000) >> 16;
         buf[4] = (secs & 0xFF000000) >> 24;
+        buf[5] = 0;     /* set control reg to enable counting */
 
-        xfer = i2c_master_send(client, buf, 5);
-        if (xfer != 5) {
+        xfer = i2c_master_send(client, buf, 6);
+        if (xfer != 6) {
                 dev_err(&client->dev, "%s: send: %d\n", __FUNCTION__, xfer);
                 return -EIO;
         }
@@ -120,6 +122,44 @@ static int ds1672_rtc_set_mmss(struct device *dev, unsigned long secs)
         return ds1672_set_mmss(to_i2c_client(dev), secs);
 }
 
+static int ds1672_get_control(struct i2c_client *client, u8 *status)
+{
+        unsigned char addr = DS1672_REG_CONTROL;
+
+        struct i2c_msg msgs[] = {
+                { client->addr, 0, 1, &addr },          /* setup read ptr */
+                { client->addr, I2C_M_RD, 1, status },  /* read control */
+        };
+
+        /* read control register */
+        if ((i2c_transfer(client->adapter, &msgs[0], 2)) != 2) {
+                dev_err(&client->dev, "%s: read error\n", __FUNCTION__);
+                return -EIO;
+        }
+
+        return 0;
+}
+
+/* following are the sysfs callback functions */
+static ssize_t show_control(struct device *dev, struct device_attribute *attr, char *buf)
+{
+        struct i2c_client *client = to_i2c_client(dev);
+        char *state = "enabled";
+        u8 control;
+        int err;
+
+        err = ds1672_get_control(client, &control);
+        if (err)
+                return err;
+
+        if (control & DS1672_REG_CONTROL_EOSC)
+                state = "disabled";
+
+        return sprintf(buf, "%s\n", state);
+}
+
+static DEVICE_ATTR(control, S_IRUGO, show_control, NULL);
+
 static struct rtc_class_ops ds1672_rtc_ops = {
         .read_time      = ds1672_rtc_read_time,
         .set_time       = ds1672_rtc_set_time,
@@ -162,6 +202,7 @@ static struct i2c_driver ds1672_driver = {
 static int ds1672_probe(struct i2c_adapter *adapter, int address, int kind)
 {
         int err = 0;
+        u8 control;
         struct i2c_client *client;
         struct rtc_device *rtc;
 
@@ -202,6 +243,20 @@ static int ds1672_probe(struct i2c_adapter *adapter, int address, int kind)
 
         i2c_set_clientdata(client, rtc);
 
+        /* read control register */
+        err = ds1672_get_control(client, &control);
+        if (err) {
+                dev_err(&client->dev, "%s: read error\n", __FUNCTION__);
+                goto exit_detach;
+        }
+
+        if (control & DS1672_REG_CONTROL_EOSC)
+                dev_warn(&client->dev, "Oscillator not enabled. "
+                                        "Set time to enable.\n");
+
+        /* Register sysfs hooks */
+        device_create_file(&client->dev, &dev_attr_control);
+
         return 0;
 
 exit_detach: