rtc: pcf8563: stop caching voltage_low

voltage_low is only updated when reading the time, this means that using
RTC_VL_READ will miss the VL flag if the time has not been read before
using the ioctl. Always read the status from the hardware.

Link: https://lore.kernel.org/r/20191214220259.621996-9-alexandre.belloni@bootlin.comSigned-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>

drivers/rtc/rtc-pcf8563.c

@@ -76,7 +76,6 @@ 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 */
 
 	struct i2c_client *client;
 #ifdef CONFIG_COMMON_CLK
@@ -208,7 +207,6 @@ static int pcf8563_rtc_read_time(struct device *dev, struct rtc_time *tm)
 		return err;
 
 	if (buf[PCF8563_REG_SC] & PCF8563_SC_LV) {
-		pcf8563->voltage_low = 1;
 		dev_err(&client->dev,
 			"low voltage detected, date/time is not reliable.\n");
 		return -EINVAL;
@@ -278,15 +276,19 @@ static int pcf8563_rtc_set_time(struct device *dev, struct rtc_time *tm)
 
 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 i2c_client *client = to_i2c_client(dev);
+	int vl, ret;
 
 	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)))
+		ret = i2c_smbus_read_byte_data(client, PCF8563_REG_SC);
+		if (ret < 0)
+			return ret;
+
+		vl = ret & PCF8563_SC_LV ? 1 : 0;
+
+		if (copy_to_user((void __user *)arg, &vl, sizeof(int)))
 			return -EFAULT;
 		return 0;
 	default: