rtc: sc27xx: Always read normal alarm when registering RTC device

When registering one RTC device, it will check to see if there is an
alarm already set in RTC hardware by reading RTC alarm, at this time
we should always read the normal alarm put in always-on region by
checking the rtc->registered flag.
Signed-off-by: Baolin Wang <baolin.wang@linaro.org>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>

drivers/rtc/rtc-sc27xx.c

@@ -415,10 +415,14 @@ static int sprd_rtc_read_alarm(struct device *dev, struct rtc_wkalrm *alrm)
 	u32 val;
 
 	/*
-	 * If aie_timer is enabled, we should get the normal alarm time.
+	 * Before RTC device is registered, it will check to see if there is an
+	 * alarm already set in RTC hardware, and we always read the normal
+	 * alarm at this time.
+	 *
+	 * Or if aie_timer is enabled, we should get the normal alarm time.
 	 * Otherwise we should get auxiliary alarm time.
 	 */
-	if (rtc->rtc && rtc->rtc->aie_timer.enabled == 0)
+	if (rtc->rtc && rtc->rtc->registered && rtc->rtc->aie_timer.enabled == 0)
 		return sprd_rtc_read_aux_alarm(dev, alrm);
 
 	ret = sprd_rtc_get_secs(rtc, SPRD_RTC_ALARM, &secs);