1 files changed, 44 insertions, 4 deletions

diff --git a/drivers/rtc/rtc-rk808.c b/drivers/rtc/rtc-rk808.c
index 91ca0bc1b484..35c9aada07c8 100644
--- a/drivers/rtc/rtc-rk808.c
+++ b/drivers/rtc/rtc-rk808.c
@@ -56,6 +56,42 @@ struct rk808_rtc {
         int irq;
 };
 
+/*
+ * The Rockchip calendar used by the RK808 counts November with 31 days. We use
+ * these translation functions to convert its dates to/from the Gregorian
+ * calendar used by the rest of the world. We arbitrarily define Jan 1st, 2016
+ * as the day when both calendars were in sync, and treat all other dates
+ * relative to that.
+ * NOTE: Other system software (e.g. firmware) that reads the same hardware must
+ * implement this exact same conversion algorithm, with the same anchor date.
+ */
+static time64_t nov2dec_transitions(struct rtc_time *tm)
+{
+        return (tm->tm_year + 1900) - 2016 + (tm->tm_mon + 1 > 11 ? 1 : 0);
+}
+
+static void rockchip_to_gregorian(struct rtc_time *tm)
+{
+        /* If it's Nov 31st, rtc_tm_to_time64() will count that like Dec 1st */
+        time64_t time = rtc_tm_to_time64(tm);
+        rtc_time64_to_tm(time + nov2dec_transitions(tm) * 86400, tm);
+}
+
+static void gregorian_to_rockchip(struct rtc_time *tm)
+{
+        time64_t extra_days = nov2dec_transitions(tm);
+        time64_t time = rtc_tm_to_time64(tm);
+        rtc_time64_to_tm(time - extra_days * 86400, tm);
+
+        /* Compensate if we went back over Nov 31st (will work up to 2381) */
+        if (nov2dec_transitions(tm) < extra_days) {
+                if (tm->tm_mon + 1 == 11)
+                        tm->tm_mday++;  /* This may result in 31! */
+                else
+                        rtc_time64_to_tm(time - (extra_days - 1) * 86400, tm);
+        }
+}
+
 /* Read current time and date in RTC */
 static int rk808_rtc_readtime(struct device *dev, struct rtc_time *tm)
 {
@@ -101,9 +137,10 @@ static int rk808_rtc_readtime(struct device *dev, struct rtc_time *tm)
         tm->tm_mon = (bcd2bin(rtc_data[4] & MONTHS_REG_MSK)) - 1;
         tm->tm_year = (bcd2bin(rtc_data[5] & YEARS_REG_MSK)) + 100;
         tm->tm_wday = bcd2bin(rtc_data[6] & WEEKS_REG_MSK);
+        rockchip_to_gregorian(tm);
         dev_dbg(dev, "RTC date/time %4d-%02d-%02d(%d) %02d:%02d:%02d\n",
                 1900 + tm->tm_year, tm->tm_mon + 1, tm->tm_mday,
-                tm->tm_wday, tm->tm_hour , tm->tm_min, tm->tm_sec);
+                tm->tm_wday, tm->tm_hour, tm->tm_min, tm->tm_sec);
 
         return ret;
 }
@@ -116,6 +153,10 @@ static int rk808_rtc_set_time(struct device *dev, struct rtc_time *tm)
         u8 rtc_data[NUM_TIME_REGS];
         int ret;
 
+        dev_dbg(dev, "set RTC date/time %4d-%02d-%02d(%d) %02d:%02d:%02d\n",
+                1900 + tm->tm_year, tm->tm_mon + 1, tm->tm_mday,
+                tm->tm_wday, tm->tm_hour, tm->tm_min, tm->tm_sec);
+        gregorian_to_rockchip(tm);
         rtc_data[0] = bin2bcd(tm->tm_sec);
         rtc_data[1] = bin2bcd(tm->tm_min);
         rtc_data[2] = bin2bcd(tm->tm_hour);
@@ -123,9 +164,6 @@ static int rk808_rtc_set_time(struct device *dev, struct rtc_time *tm)
         rtc_data[4] = bin2bcd(tm->tm_mon + 1);
         rtc_data[5] = bin2bcd(tm->tm_year - 100);
         rtc_data[6] = bin2bcd(tm->tm_wday);
-        dev_dbg(dev, "set RTC date/time %4d-%02d-%02d(%d) %02d:%02d:%02d\n",
-                1900 + tm->tm_year, tm->tm_mon + 1, tm->tm_mday,
-                tm->tm_wday, tm->tm_hour , tm->tm_min, tm->tm_sec);
 
         /* Stop RTC while updating the RTC registers */
         ret = regmap_update_bits(rk808->regmap, RK808_RTC_CTRL_REG,
@@ -170,6 +208,7 @@ static int rk808_rtc_readalarm(struct device *dev, struct rtc_wkalrm *alrm)
         alrm->time.tm_mday = bcd2bin(alrm_data[3] & DAYS_REG_MSK);
         alrm->time.tm_mon = (bcd2bin(alrm_data[4] & MONTHS_REG_MSK)) - 1;
         alrm->time.tm_year = (bcd2bin(alrm_data[5] & YEARS_REG_MSK)) + 100;
+        rockchip_to_gregorian(&alrm->time);
 
         ret = regmap_read(rk808->regmap, RK808_RTC_INT_REG, &int_reg);
         if (ret) {
@@ -227,6 +266,7 @@ static int rk808_rtc_setalarm(struct device *dev, struct rtc_wkalrm *alrm)
                 alrm->time.tm_mday, alrm->time.tm_wday, alrm->time.tm_hour,
                 alrm->time.tm_min, alrm->time.tm_sec);
 
+        gregorian_to_rockchip(&alrm->time);
         alrm_data[0] = bin2bcd(alrm->time.tm_sec);
         alrm_data[1] = bin2bcd(alrm->time.tm_min);
         alrm_data[2] = bin2bcd(alrm->time.tm_hour);