| Message ID | 20170330212130.30548-1-paul.burton@imgtec.com |
|---|---|
| State | Rejected |
| Headers | show |
On 30/03/2017 at 14:21:30 -0700, Paul Burton wrote: > The oscillator failure bit of the flags register defaults to 1 when the > m41t80 RTC device is powered up. If we don't clear it as the manual says > we should then the bit remains set permanently and since commit > 05a7f27a889f ("rtc: m41t80: handle oscillator failure bit") we spam the > kernel console with an error message on every attempt to read the RTC, > for example: > > Welcome to Buildroot > mips64r6-n32-le-hf-soak login: [ 15.534459] rtc-m41t80 0-0068: > Oscillator failure, data is invalid. > [ 16.526308] rtc-m41t80 0-0068: Oscillator failure, data is invalid. > [ 19.534342] rtc-m41t80 0-0068: Oscillator failure, data is invalid. > [ 20.526327] rtc-m41t80 0-0068: Oscillator failure, data is invalid. > That is the expected behavior. If power failed at some point you shouldn't read the RTC until you set time again. I would agree that the message is kind of overkill but I usually let the decision to the driver author. > Fix this by clearing the OF flag during probe, as the m41t80 manual > says we ought to. > No, clearing this bit in probe destroys valuable information. > Signed-off-by: Paul Burton <paul.burton@imgtec.com> > Fixes: 05a7f27a889f ("rtc: m41t80: handle oscillator failure bit") > Cc: Alessandro Zummo <a.zummo@towertech.it> > Cc: Alexandre Belloni <alexandre.belloni@free-electrons.com> > Cc: Mylčne Josserand <mylene.josserand@free-electrons.com> > Cc: rtc-linux@googlegroups.com > Cc: <stable@vger.kernel.org> # v4.7+ > > --- > > drivers/rtc/rtc-m41t80.c | 11 +++++++++++ > 1 file changed, 11 insertions(+) > > diff --git a/drivers/rtc/rtc-m41t80.c b/drivers/rtc/rtc-m41t80.c > index 58698d21c2c3..33be6e4694f6 100644 > --- a/drivers/rtc/rtc-m41t80.c > +++ b/drivers/rtc/rtc-m41t80.c > @@ -813,6 +813,17 @@ static int m41t80_probe(struct i2c_client *client, > > m41t80_data->rtc = rtc; > > + /* Clear the OF (Oscillator failure) bit, which is 1 on power up */ > + rc = i2c_smbus_read_byte_data(client, M41T80_REG_FLAGS); > + if (rc < 0) { > + dev_warn(&client->dev, "unable to read flags"); > + } else if (rc & M41T80_FLAGS_OF) { > + rc &= ~M41T80_FLAGS_OF; > + rc = i2c_smbus_write_byte_data(client, M41T80_REG_FLAGS, rc); > + if (rc) > + dev_warn(&client->dev, "unable to clear OF flag"); > + } > + > /* Make sure HT (Halt Update) bit is cleared */ > rc = i2c_smbus_read_byte_data(client, M41T80_REG_ALARM_HOUR); > > -- > 2.12.1 >
diff --git a/drivers/rtc/rtc-m41t80.c b/drivers/rtc/rtc-m41t80.c index 58698d21c2c3..33be6e4694f6 100644 --- a/drivers/rtc/rtc-m41t80.c +++ b/drivers/rtc/rtc-m41t80.c @@ -813,6 +813,17 @@ static int m41t80_probe(struct i2c_client *client, m41t80_data->rtc = rtc; + /* Clear the OF (Oscillator failure) bit, which is 1 on power up */ + rc = i2c_smbus_read_byte_data(client, M41T80_REG_FLAGS); + if (rc < 0) { + dev_warn(&client->dev, "unable to read flags"); + } else if (rc & M41T80_FLAGS_OF) { + rc &= ~M41T80_FLAGS_OF; + rc = i2c_smbus_write_byte_data(client, M41T80_REG_FLAGS, rc); + if (rc) + dev_warn(&client->dev, "unable to clear OF flag"); + } + /* Make sure HT (Halt Update) bit is cleared */ rc = i2c_smbus_read_byte_data(client, M41T80_REG_ALARM_HOUR);
The oscillator failure bit of the flags register defaults to 1 when the m41t80 RTC device is powered up. If we don't clear it as the manual says we should then the bit remains set permanently and since commit 05a7f27a889f ("rtc: m41t80: handle oscillator failure bit") we spam the kernel console with an error message on every attempt to read the RTC, for example: Welcome to Buildroot mips64r6-n32-le-hf-soak login: [ 15.534459] rtc-m41t80 0-0068: Oscillator failure, data is invalid. [ 16.526308] rtc-m41t80 0-0068: Oscillator failure, data is invalid. [ 19.534342] rtc-m41t80 0-0068: Oscillator failure, data is invalid. [ 20.526327] rtc-m41t80 0-0068: Oscillator failure, data is invalid. Fix this by clearing the OF flag during probe, as the m41t80 manual says we ought to. Signed-off-by: Paul Burton <paul.burton@imgtec.com> Fixes: 05a7f27a889f ("rtc: m41t80: handle oscillator failure bit") Cc: Alessandro Zummo <a.zummo@towertech.it> Cc: Alexandre Belloni <alexandre.belloni@free-electrons.com> Cc: Mylène Josserand <mylene.josserand@free-electrons.com> Cc: rtc-linux@googlegroups.com Cc: <stable@vger.kernel.org> # v4.7+ --- drivers/rtc/rtc-m41t80.c | 11 +++++++++++ 1 file changed, 11 insertions(+)