> Currently, we enable the device before we enable the device trigger. At
> high frequencies, this can cause interrupts that don't yet have a poll
> function associated with them and are thus treated as spurious. At high
> frequencies with level interrupts, this can even cause an interrupt storm
> of repeated spurious interrupts (~100,000 on my Beagleboard with the
> LSM9DS1 magnetometer). If these repeat too much, the interrupt will get
> disabled and the device will stop functioning.
>
> To prevent these problems, enable the device prior to enabling the device
> trigger, and disable the divec prior to disabling the trigger. This means
> there's no window of time during which the device creates interrupts but we
> have no trigger to answer them.
>
I have just reviewed the code (not carried out any tests) and I guess this patch
is correct. Moreover if the memory allocation in st_magn_buffer_postenable fails
we will end up with a device generating interrupts without any buffer
to collect data.
I guess there is the same issue in st_magn_buffer_predisable(), if
st_sensors_set_enable
or iio_triggered_buffer_predisable fails, should we remove the data
buffer? Maybe we
just skip return code from st_sensors_set_enable.
@Denis: any hints?
Regards,
Lorenzo
> Signed-off-by: Martin Kelly <martin@xxxxxxxxxxxxxxxx>
> ---
> drivers/iio/magnetometer/st_magn_buffer.c | 12 +++---------
> 1 file changed, 3 insertions(+), 9 deletions(-)
>
> diff --git a/drivers/iio/magnetometer/st_magn_buffer.c b/drivers/iio/magnetometer/st_magn_buffer.c
> index 0a9e8fadfa9d..37ab30566464 100644
> --- a/drivers/iio/magnetometer/st_magn_buffer.c
> +++ b/drivers/iio/magnetometer/st_magn_buffer.c
> @@ -30,11 +30,6 @@ int st_magn_trig_set_state(struct iio_trigger *trig, bool state)
> return st_sensors_set_dataready_irq(indio_dev, state);
> }
>
> -static int st_magn_buffer_preenable(struct iio_dev *indio_dev)
> -{
> - return st_sensors_set_enable(indio_dev, true);
> -}
> -
> static int st_magn_buffer_postenable(struct iio_dev *indio_dev)
> {
> int err;
> @@ -50,7 +45,7 @@ static int st_magn_buffer_postenable(struct iio_dev *indio_dev)
> if (err < 0)
> goto st_magn_buffer_postenable_error;
>
> - return err;
> + return st_sensors_set_enable(indio_dev, true);
>
> st_magn_buffer_postenable_error:
> kfree(mdata->buffer_data);
> @@ -63,11 +58,11 @@ static int st_magn_buffer_predisable(struct iio_dev *indio_dev)
> int err;
> struct st_sensor_data *mdata = iio_priv(indio_dev);
>
> - err = iio_triggered_buffer_predisable(indio_dev);
> + err = st_sensors_set_enable(indio_dev, false);
> if (err < 0)
> goto st_magn_buffer_predisable_error;
>
> - err = st_sensors_set_enable(indio_dev, false);
> + err = iio_triggered_buffer_predisable(indio_dev);
>
> st_magn_buffer_predisable_error:
> kfree(mdata->buffer_data);
> @@ -75,7 +70,6 @@ static int st_magn_buffer_predisable(struct iio_dev *indio_dev)
> }
>
> static const struct iio_buffer_setup_ops st_magn_buffer_setup_ops = {
> - .preenable = &st_magn_buffer_preenable,
> .postenable = &st_magn_buffer_postenable,
> .predisable = &st_magn_buffer_predisable,
> };
> --
> 2.11.0
>
--
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