rtc: davinci: let the core handle rtc range

Let the core handle offsetting and windowing the RTC range.

This rtc has hours, minutes, seconds and 16bit days. As the driver has the
RTC epoch set to year 2000, this means that the end of the range is 2^16
days minus one second later. This is Sun Jun  6 23:59:59 UTC 2179. This
is better than the currently set year 2099.

Link: https://lore.kernel.org/r/20200305215022.32533-3-alexandre.belloni@bootlin.comSigned-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>

drivers/rtc/rtc-davinci.c

@@ -258,10 +258,6 @@ static int convert2days(u16 *days, struct rtc_time *tm)
 	int i;
 	*days = 0;
 
-	/* epoch == 1900 */
-	if (tm->tm_year < 100 || tm->tm_year > 199)
-		return -EINVAL;
-
 	for (i = 2000; i < 1900 + tm->tm_year; i++)
 		*days += rtc_year_days(1, 12, i);
 
@@ -313,8 +309,7 @@ static int davinci_rtc_set_time(struct device *dev, struct rtc_time *tm)
 	u8 rtc_cctrl;
 	unsigned long flags;
 
-	if (convert2days(&days, tm) < 0)
-		return -EINVAL;
+	convert2days(&days, tm);
 
 	spin_lock_irqsave(&davinci_rtc_lock, flags);
 
@@ -413,8 +408,7 @@ static int davinci_rtc_set_alarm(struct device *dev, struct rtc_wkalrm *alm)
 	unsigned long flags;
 	u16 days;
 
-	if (convert2days(&days, &alm->time) < 0)
-		return -EINVAL;
+	convert2days(&days, &alm->time);
 
 	spin_lock_irqsave(&davinci_rtc_lock, flags);
 
@@ -469,6 +463,8 @@ static int __init davinci_rtc_probe(struct platform_device *pdev)
 		return PTR_ERR(davinci_rtc->rtc);
 
 	davinci_rtc->rtc->ops = &davinci_rtc_ops;
+	davinci_rtc->rtc->range_min = RTC_TIMESTAMP_BEGIN_2000;
+	davinci_rtc->rtc->range_max = RTC_TIMESTAMP_BEGIN_2000 + (1 << 16) * 86400ULL - 1;
 
 	rtcif_write(davinci_rtc, PRTCIF_INTFLG_RTCSS, PRTCIF_INTFLG);
 	rtcif_write(davinci_rtc, 0, PRTCIF_INTEN);