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: Stefan Agner <ste...@agner.ch>
---
Documentation/devicetree/bindings/i2c/trivial-devices.txt | 1 +
drivers/rtc/rtc-ds1307.c | 13 +++++++++++++
2 files changed, 14 insertions(+)
diff --git a/Documentation/devicetree/bindings/i2c/trivial-devices.txt
b/Documentation/devicetree/bindings/i2c/trivial-devices.txt
index ad10fbe61562..3e0a34c88e07 100644
--- a/Documentation/devicetree/bindings/i2c/trivial-devices.txt
+++ b/Documentation/devicetree/bindings/i2c/trivial-devices.txt
@@ -160,6 +160,7 @@ sii,s35390a 2-wire CMOS real-time clock
silabs,si7020 Relative Humidity and Temperature Sensors
skyworks,sky81452 Skyworks SKY81452: Six-Channel White LED Driver with
Touch Panel Bias Supply
st,24c256 i2c serial eeprom (24cxx)
+st,m41t0 Serial real-time clock (RTC)
st,m41t00 Serial real-time clock (RTC)
st,m41t62 Serial real-time clock (RTC) with alarm
st,m41t80 M41T80 - SERIAL ACCESS RTC WITH ALARMS
diff --git a/drivers/rtc/rtc-ds1307.c b/drivers/rtc/rtc-ds1307.c
index 4ad97be48043..93b1e558fd54 100644
--- a/drivers/rtc/rtc-ds1307.c
+++ b/drivers/rtc/rtc-ds1307.c
@@ -38,6 +38,7 @@ enum ds_type {
ds_1340,
ds_1388,
ds_3231,
+ m41t0,
m41t00,
mcp794xx,
rx_8025,
@@ -52,6 +53,7 @@ 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 */
@@ -182,6 +184,7 @@ 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 },
@@ -201,6 +204,7 @@ static const struct acpi_device_id ds1307_acpi_ids[] = {
{ .id = "DS1388", .driver_data = ds_1388 },
{ .id = "DS1340", .driver_data = ds_1340 },
{ .id = "DS3231", .driver_data = ds_3231 },
+ { .id = "M41T0", .driver_data = m41t0 },
{ .id = "M41T00", .driver_data = m41t00 },
{ .id = "MCP7940X", .driver_data = mcp794xx },
{ .id = "MCP7941X", .driver_data = mcp794xx },
@@ -396,6 +400,13 @@ 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;
@@ -1513,6 +1524,7 @@ static int ds1307_probe(struct i2c_client *client,
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) {
@@ -1577,6 +1589,7 @@ static int ds1307_probe(struct i2c_client *client,
tmp = ds1307->regs[DS1307_REG_HOUR];
switch (ds1307->type) {
case ds_1340:
+ case m41t0:
case m41t00:
/*
* NOTE: ignores century bits; fix before deploying
--
2.12.0
