rtc: rv8803: initialize registers on post-probe voltage loss

The driver probe currently initializes some registers to non-POR
values. These values are not reinstated if the RTC experiences voltage
loss later on. Fix this.
Signed-off-by: Ahmad Fatoum <a.fatoum@pengutronix.de>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Link: https://lore.kernel.org/r/20220426071056.1187235-3-s.hauer@pengutronix.de

drivers/rtc/rtc-rv8803.c

@@ -137,6 +137,13 @@ static int rv8803_write_regs(const struct i2c_client *client,
 	return ret;
 }
 
+static int rv8803_regs_configure(struct rv8803_data *rv8803);
+
+static int rv8803_regs_reset(struct rv8803_data *rv8803)
+{
+	return rv8803_regs_configure(rv8803);
+}
+
 static irqreturn_t rv8803_handle_irq(int irq, void *dev_id)
 {
 	struct i2c_client *client = dev_id;
@@ -270,6 +277,12 @@ static int rv8803_set_time(struct device *dev, struct rtc_time *tm)
 		return flags;
 	}
 
+	if (flags & RV8803_FLAG_V2F) {
+		ret = rv8803_regs_reset(rv8803);
+		if (ret)
+			return ret;
+	}
+
 	ret = rv8803_write_reg(rv8803->client, RV8803_FLAG,
 			       flags & ~(RV8803_FLAG_V1F | RV8803_FLAG_V2F));