rtc: pm8xxx: Read ALARM_EN and update to alarm enabled status

ALARM_EN status is retained in PMIC register after device shutdown
if poweron_alarm is enabled. Read it to make sure the driver has
consistent value with the register status.
Signed-off-by: Guixiong Wei <guixiong@codeaurora.org>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Link: https://lore.kernel.org/r/1608809337-18852-1-git-send-email-guixiong@codeaurora.org

drivers/rtc/rtc-pm8xxx.c

@@ -20,6 +20,7 @@
 /* RTC_CTRL register bit fields */
 #define PM8xxx_RTC_ENABLE		BIT(7)
 #define PM8xxx_RTC_ALARM_CLEAR		BIT(0)
+#define PM8xxx_RTC_ALARM_ENABLE		BIT(7)
 
 #define NUM_8_BIT_RTC_REGS		0x4
 
@@ -265,6 +266,7 @@ static int pm8xxx_rtc_set_alarm(struct device *dev, struct rtc_wkalrm *alarm)
 static int pm8xxx_rtc_read_alarm(struct device *dev, struct rtc_wkalrm *alarm)
 {
 	int rc;
+	unsigned int ctrl_reg;
 	u8 value[NUM_8_BIT_RTC_REGS];
 	unsigned long secs;
 	struct pm8xxx_rtc *rtc_dd = dev_get_drvdata(dev);
@@ -282,6 +284,13 @@ static int pm8xxx_rtc_read_alarm(struct device *dev, struct rtc_wkalrm *alarm)
 
 	rtc_time64_to_tm(secs, &alarm->time);
 
+	rc = regmap_read(rtc_dd->regmap, regs->alarm_ctrl, &ctrl_reg);
+	if (rc) {
+		dev_err(dev, "Read from RTC alarm control register failed\n");
+		return rc;
+	}
+	alarm->enabled = !!(ctrl_reg & PM8xxx_RTC_ALARM_ENABLE);
+
 	dev_dbg(dev, "Alarm set for - h:m:s=%ptRt, y-m-d=%ptRdr\n",
 		&alarm->time, &alarm->time);