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-rw-r--r--Documentation/devicetree/bindings/i2c/trivial-devices.txt1
-rw-r--r--drivers/rtc/rtc-ds1307.c12
2 files changed, 13 insertions, 0 deletions
diff --git a/Documentation/devicetree/bindings/i2c/trivial-devices.txt b/Documentation/devicetree/bindings/i2c/trivial-devices.txt
index c50cf13c852e..aee63eb6a3b6 100644
--- a/Documentation/devicetree/bindings/i2c/trivial-devices.txt
+++ b/Documentation/devicetree/bindings/i2c/trivial-devices.txt
@@ -92,6 +92,7 @@ sgx,vz89x SGX Sensortech VZ89X Sensors
sii,s35390a 2-wire CMOS real-time clock
skyworks,sky81452 Skyworks SKY81452: Six-Channel White LED Driver with Touch Panel Bias Supply
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 aa705bb4748c..097ca2a8565f 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,
mcp794xx,
rx_8025,
@@ -48,6 +49,7 @@ enum ds_type {
# define DS1340_BIT_nEOSC 0x80
# define MCP794XX_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 */
@@ -174,6 +176,7 @@ static const struct i2c_device_id ds1307_id[] = {
{ "ds1388", ds_1388 },
{ "ds1340", ds_1340 },
{ "ds3231", ds_3231 },
+ { "m41t0", m41t0 },
{ "m41t00", m41t00 },
{ "mcp7940x", mcp794xx },
{ "mcp7941x", mcp794xx },
@@ -363,6 +366,13 @@ 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_once(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;
@@ -1044,6 +1054,7 @@ 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) {
@@ -1108,6 +1119,7 @@ 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