1 files changed, 43 insertions, 1 deletions

diff --git a/drivers/rtc/rtc-pcf8563.c b/drivers/rtc/rtc-pcf8563.c
index bc0677de1996..97a3284bb7c6 100644
--- a/drivers/rtc/rtc-pcf8563.c
+++ b/drivers/rtc/rtc-pcf8563.c
@@ -64,6 +64,7 @@ struct pcf8563 {
          * 1970...2069.
          */
         int c_polarity; /* 0: MO_C=1 means 19xx, otherwise MO_C=1 means 20xx */
+        int voltage_low; /* incicates if a low_voltage was detected */
 };
 
 /*
@@ -86,9 +87,11 @@ static int pcf8563_get_datetime(struct i2c_client *client, struct rtc_time *tm)
                 return -EIO;
         }
 
-        if (buf[PCF8563_REG_SC] & PCF8563_SC_LV)
+        if (buf[PCF8563_REG_SC] & PCF8563_SC_LV) {
+                pcf8563->voltage_low = 1;
                 dev_info(&client->dev,
                         "low voltage detected, date/time is not reliable.\n");
+        }
 
         dev_dbg(&client->dev,
                 "%s: raw data is st1=%02x, st2=%02x, sec=%02x, min=%02x, hr=%02x, "
@@ -173,6 +176,44 @@ static int pcf8563_set_datetime(struct i2c_client *client, struct rtc_time *tm)
         return 0;
 }
 
+#ifdef CONFIG_RTC_INTF_DEV
+static int pcf8563_rtc_ioctl(struct device *dev, unsigned int cmd, unsigned long arg)
+{
+        struct pcf8563 *pcf8563 = i2c_get_clientdata(to_i2c_client(dev));
+        struct rtc_time tm;
+
+        switch (cmd) {
+        case RTC_VL_READ:
+                if (pcf8563->voltage_low)
+                        dev_info(dev, "low voltage detected, date/time is not reliable.\n");
+
+                if (copy_to_user((void __user *)arg, &pcf8563->voltage_low,
+                                        sizeof(int)))
+                        return -EFAULT;
+                return 0;
+        case RTC_VL_CLR:
+                /*
+                 * Clear the VL bit in the seconds register in case
+                 * the time has not been set already (which would
+                 * have cleared it). This does not really matter
+                 * because of the cached voltage_low value but do it
+                 * anyway for consistency.
+                 */
+                if (pcf8563_get_datetime(to_i2c_client(dev), &tm))
+                        pcf8563_set_datetime(to_i2c_client(dev), &tm);
+
+                /* Clear the cached value. */
+                pcf8563->voltage_low = 0;
+
+                return 0;
+        default:
+                return -ENOIOCTLCMD;
+        }
+}
+#else
+#define pcf8563_rtc_ioctl NULL
+#endif
+
 static int pcf8563_rtc_read_time(struct device *dev, struct rtc_time *tm)
 {
         return pcf8563_get_datetime(to_i2c_client(dev), tm);
@@ -184,6 +225,7 @@ static int pcf8563_rtc_set_time(struct device *dev, struct rtc_time *tm)
 }
 
 static const struct rtc_class_ops pcf8563_rtc_ops = {
+        .ioctl          = pcf8563_rtc_ioctl,
         .read_time      = pcf8563_rtc_read_time,
         .set_time       = pcf8563_rtc_set_time,
 };