From 50d6c0ea8111100a102c03b4410ba1e45fa8b771 Mon Sep 17 00:00:00 2001 From: Alexandre Belloni Date: Wed, 13 Jul 2016 02:26:08 +0200 Subject: [PATCH] rtc: ds1307: fix century bit support Add an option to properly support the century bit of ds1337 and compatibles and ds1340. Because the driver had a bug until now, it is not possible to switch users to the fixed code directly as RTCs in the field will wrongly have the century bit set. Acked-by: Arnaud Ebalard Signed-off-by: Alexandre Belloni --- drivers/rtc/Kconfig | 14 ++++++++++++ drivers/rtc/rtc-ds1307.c | 48 +++++++++++++++++++++++++++++++++++----- 2 files changed, 57 insertions(+), 5 deletions(-) diff --git a/drivers/rtc/Kconfig b/drivers/rtc/Kconfig index 7fc11cdfd27e..6ce3dad73253 100644 --- a/drivers/rtc/Kconfig +++ b/drivers/rtc/Kconfig @@ -234,6 +234,20 @@ config RTC_DRV_DS1307_HWMON Say Y here if you want to expose temperature sensor data on rtc-ds1307 (only DS3231) +config RTC_DRV_DS1307_CENTURY + bool "Century bit support for rtc-ds1307" + depends on RTC_DRV_DS1307 + default n + help + The DS1307 driver suffered from a bug where it was enabling the + century bit inconditionnally but never used it when reading the time. + It made the driver unable to support dates beyond 2099. + Setting this option will add proper support for the century bit but if + the time was previously set using a kernel predating this option, + reading the date will return a date in the next century. + To solve that, you could boot a kernel without this option set, set + the RTC date and then boot a kernel with this option set. + config RTC_DRV_DS1374 tristate "Dallas/Maxim DS1374" help diff --git a/drivers/rtc/rtc-ds1307.c b/drivers/rtc/rtc-ds1307.c index 8e1c5cb6ece6..712e221d2415 100644 --- a/drivers/rtc/rtc-ds1307.c +++ b/drivers/rtc/rtc-ds1307.c @@ -382,10 +382,25 @@ static int ds1307_get_time(struct device *dev, struct rtc_time *t) t->tm_mday = bcd2bin(ds1307->regs[DS1307_REG_MDAY] & 0x3f); tmp = ds1307->regs[DS1307_REG_MONTH] & 0x1f; t->tm_mon = bcd2bin(tmp) - 1; - - /* assume 20YY not 19YY, and ignore DS1337_BIT_CENTURY */ t->tm_year = bcd2bin(ds1307->regs[DS1307_REG_YEAR]) + 100; +#ifdef CONFIG_RTC_DRV_DS1307_CENTURY + switch (ds1307->type) { + case ds_1337: + case ds_1339: + case ds_3231: + if (ds1307->regs[DS1307_REG_MONTH] & DS1337_BIT_CENTURY) + t->tm_year += 100; + break; + case ds_1340: + if (ds1307->regs[DS1307_REG_HOUR] & DS1340_BIT_CENTURY) + t->tm_year += 100; + break; + default: + break; + } +#endif + dev_dbg(dev, "%s secs=%d, mins=%d, " "hours=%d, mday=%d, mon=%d, year=%d, wday=%d\n", "read", t->tm_sec, t->tm_min, @@ -409,6 +424,27 @@ static int ds1307_set_time(struct device *dev, struct rtc_time *t) t->tm_hour, t->tm_mday, t->tm_mon, t->tm_year, t->tm_wday); +#ifdef CONFIG_RTC_DRV_DS1307_CENTURY + if (t->tm_year < 100) + return -EINVAL; + + switch (ds1307->type) { + case ds_1337: + case ds_1339: + case ds_3231: + case ds_1340: + if (t->tm_year > 299) + return -EINVAL; + default: + if (t->tm_year > 199) + return -EINVAL; + break; + } +#else + if (t->tm_year < 100 || t->tm_year > 199) + return -EINVAL; +#endif + buf[DS1307_REG_SECS] = bin2bcd(t->tm_sec); buf[DS1307_REG_MIN] = bin2bcd(t->tm_min); buf[DS1307_REG_HOUR] = bin2bcd(t->tm_hour); @@ -424,11 +460,13 @@ static int ds1307_set_time(struct device *dev, struct rtc_time *t) case ds_1337: case ds_1339: case ds_3231: - buf[DS1307_REG_MONTH] |= DS1337_BIT_CENTURY; + if (t->tm_year > 199) + buf[DS1307_REG_MONTH] |= DS1337_BIT_CENTURY; break; case ds_1340: - buf[DS1307_REG_HOUR] |= DS1340_BIT_CENTURY_EN - | DS1340_BIT_CENTURY; + buf[DS1307_REG_HOUR] |= DS1340_BIT_CENTURY_EN; + if (t->tm_year > 199) + buf[DS1307_REG_HOUR] |= DS1340_BIT_CENTURY; break; case mcp794xx: /*