In 2013 Rockchip engineers found that the Gregorian calendar contained flaws

@@ -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);

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