patch "iio:st_magn: Fix enable device after trigger" added to staging-linus

This is a note to let you know that I've just added the patch titled

iio:st_magn: Fix enable device after trigger

to my staging git tree which can be found at
git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/staging.git
in the staging-linus branch.

The patch will show up in the next release of the linux-next tree (usually sometime within the next 24 hours during the week.)

The patch will hopefully also be merged in Linus's tree for the next -rc kernel release.

If you have any questions about this process, please let me know.

From: Martin Kelly <[email protected]>
Date: Sun, 28 Oct 2018 20:18:53 -0700
Subject: iio:st_magn: Fix enable device after trigger

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.

---
 drivers/iio/magnetometer/st_magn_buffer.c | 12 +++---------
 1 file changed, 3 insertions(+), 9 deletions(-)

index 0a9e8fadfa9d..37ab30566464 100644
@@ -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,
 };

2.19.1