rtc: pcf8563: let the core handle range offsetting

Set the RTC range properly and use the core windowing and offsetting to
(unfortunately) map back to a 1970-2069 range.

Link: https://lore.kernel.org/r/20190829212547.19185-5-alexandre.belloni@bootlin.comSigned-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>

drivers/rtc/rtc-pcf8563.c

@@ -229,9 +229,7 @@ static int pcf8563_rtc_read_time(struct device *dev, struct rtc_time *tm)
 	tm->tm_mday = bcd2bin(buf[PCF8563_REG_DM] & 0x3F);
 	tm->tm_wday = buf[PCF8563_REG_DW] & 0x07;
 	tm->tm_mon = bcd2bin(buf[PCF8563_REG_MO] & 0x1F) - 1; /* rtc mn 1-12 */
-	tm->tm_year = bcd2bin(buf[PCF8563_REG_YR]);
-	if (tm->tm_year < 70)
-		tm->tm_year += 100;	/* assume we are in 1970...2069 */
+	tm->tm_year = bcd2bin(buf[PCF8563_REG_YR]) + 100;
 	/* detect the polarity heuristically. see note above. */
 	pcf8563->c_polarity = (buf[PCF8563_REG_MO] & PCF8563_MO_C) ?
 		(tm->tm_year >= 100) : (tm->tm_year < 100);
@@ -268,7 +266,7 @@ static int pcf8563_rtc_set_time(struct device *dev, struct rtc_time *tm)
 	buf[PCF8563_REG_MO] = bin2bcd(tm->tm_mon + 1);
 
 	/* year and century */
-	buf[PCF8563_REG_YR] = bin2bcd(tm->tm_year % 100);
+	buf[PCF8563_REG_YR] = bin2bcd(tm->tm_year - 100);
 	if (pcf8563->c_polarity ? (tm->tm_year >= 100) : (tm->tm_year < 100))
 		buf[PCF8563_REG_MO] |= PCF8563_MO_C;
 
@@ -590,6 +588,9 @@ static int pcf8563_probe(struct i2c_client *client,
 	pcf8563->rtc->ops = &pcf8563_rtc_ops;
 	/* the pcf8563 alarm only supports a minute accuracy */
 	pcf8563->rtc->uie_unsupported = 1;
+	pcf8563->rtc->range_min = RTC_TIMESTAMP_BEGIN_2000;
+	pcf8563->rtc->range_max = RTC_TIMESTAMP_END_2099;
+	pcf8563->rtc->set_start_time = true;
 
 	if (client->irq > 0) {
 		err = devm_request_threaded_irq(&client->dev, client->irq,