From f77e33b00691bc140412b6e9c94f90b185f0f5d7 Mon Sep 17 00:00:00 2001 From: Bhuvanchandra DV Date: Tue, 18 Jul 2017 15:32:28 +0530 Subject: rtc: ds1307: support m41t0 variant The m41t0 variant is very similar to the already supported m41t00 variant, with the notable exception of the oscillator fail bit. The data sheet notes: If the oscillator fail (OF) bit is internally set to a '1,' this indicates that the oscillator has either stopped, or was stopped for some period of time and can be used to judge the validity of the clock and date data. The bit will get cleared with a regular write of the system time, so no changes are needed to clear it. Signed-off-by: Bhuvanchandra DV (backported from commit 8566f70c8a90f3914b06e934852596ba94aaa381) --- Documentation/devicetree/bindings/i2c/trivial-devices.txt | 1 + drivers/rtc/rtc-ds1307.c | 12 ++++++++++++ 2 files changed, 13 insertions(+) diff --git a/Documentation/devicetree/bindings/i2c/trivial-devices.txt b/Documentation/devicetree/bindings/i2c/trivial-devices.txt index ad6a73852f08..7a5c7f4dd83f 100644 --- a/Documentation/devicetree/bindings/i2c/trivial-devices.txt +++ b/Documentation/devicetree/bindings/i2c/trivial-devices.txt @@ -54,6 +54,7 @@ ramtron,24c64 i2c serial eeprom (24cxx) ricoh,rs5c372a I2C bus SERIAL INTERFACE REAL-TIME CLOCK IC samsung,24ad0xd1 S524AD0XF1 (128K/256K-bit Serial EEPROM for Low Power) st-micro,24c256 i2c serial eeprom (24cxx) +st,m41t0 Serial real-time clock (RTC) stm,m41t00 Serial Access TIMEKEEPER stm,m41t62 Serial real-time clock (RTC) with alarm stm,m41t80 M41T80 - SERIAL ACCESS RTC WITH ALARMS diff --git a/drivers/rtc/rtc-ds1307.c b/drivers/rtc/rtc-ds1307.c index b53992ab3090..7a30562e0cc5 100644 --- a/drivers/rtc/rtc-ds1307.c +++ b/drivers/rtc/rtc-ds1307.c @@ -34,6 +34,7 @@ enum ds_type { ds_1340, ds_1388, ds_3231, + m41t0, m41t00, mcp7941x, rx_8025, @@ -48,6 +49,7 @@ enum ds_type { # define DS1340_BIT_nEOSC 0x80 # define MCP7941X_BIT_ST 0x80 #define DS1307_REG_MIN 0x01 /* 00-59 */ +#define M41T0_BIT_OF 0x80 #define DS1307_REG_HOUR 0x02 /* 00-23, or 1-12{am,pm} */ # define DS1307_BIT_12HR 0x40 /* in REG_HOUR */ # define DS1307_BIT_PM 0x20 /* in REG_HOUR */ @@ -168,6 +170,7 @@ static const struct i2c_device_id ds1307_id[] = { { "ds1388", ds_1388 }, { "ds1340", ds_1340 }, { "ds3231", ds_3231 }, + { "m41t0", m41t0 }, { "m41t00", m41t00 }, { "mcp7941x", mcp7941x }, { "pt7c4338", ds_1307 }, @@ -376,6 +379,13 @@ static int ds1307_get_time(struct device *dev, struct rtc_time *t) dev_dbg(dev, "%s: %7ph\n", "read", ds1307->regs); + /* if oscillator fail bit is set, no data can be trusted */ + if (ds1307->type == m41t0 && + ds1307->regs[DS1307_REG_MIN] & M41T0_BIT_OF) { + dev_warn(dev, "oscillator failed, set time!\n"); + return -EINVAL; + } + t->tm_sec = bcd2bin(ds1307->regs[DS1307_REG_SECS] & 0x7f); t->tm_min = bcd2bin(ds1307->regs[DS1307_REG_MIN] & 0x7f); tmp = ds1307->regs[DS1307_REG_HOUR] & 0x3f; @@ -837,6 +847,7 @@ read_rtc: tmp = ds1307->regs[DS1307_REG_SECS]; switch (ds1307->type) { case ds_1307: + case m41t0: case m41t00: /* clock halted? turn it on, so clock can tick. */ if (tmp & DS1307_BIT_CH) { @@ -901,6 +912,7 @@ read_rtc: tmp = ds1307->regs[DS1307_REG_HOUR]; switch (ds1307->type) { case ds_1340: + case m41t0: case m41t00: /* * NOTE: ignores century bits; fix before deploying -- cgit v1.2.3