[PATCH V2 4/8] iio: mma8452: Add support for transient event debouncing

[Martin Fuzzey <mfuzzey@parkeon.com>]

Allow the debouce counter for transient events to be configured
using the sysfs attribute events/in_accel_thresh_rising_period

Signed-off-by: Martin Fuzzey <mfuzzey@parkeon.com>
---
 drivers/iio/accel/mma8452.c |   77 ++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 75 insertions(+), 2 deletions(-)

diff --git a/drivers/iio/accel/mma8452.c b/drivers/iio/accel/mma8452.c
index 3415b36..1d1e41b 100644
--- a/drivers/iio/accel/mma8452.c
+++ b/drivers/iio/accel/mma8452.c
@@ -129,6 +129,12 @@ static int mma8452_get_int_plus_micros_index(const int (*vals)[2], int n,
 	return -EINVAL;
 }
 
+static int mma8452_get_odr_index(struct mma8452_data *data)
+{
+	return (data->ctrl_reg1 & MMA8452_CTRL_DR_MASK) >>
+			MMA8452_CTRL_DR_SHIFT;
+}
+
 static const int mma8452_samp_freq[8][2] = {
 	{800, 0}, {400, 0}, {200, 0}, {100, 0}, {50, 0}, {12, 500000},
 	{6, 250000}, {1, 560000}
@@ -144,6 +150,18 @@ static const int mma8452_scales[3][2] = {
 	{0, 9577}, {0, 19154}, {0, 38307}
 };
 
+/* Datasheet table 35  (step time vs sample frequency) */
+static const int mma8452_transient_time_step_us[8] = {
+	1250,
+	2500,
+	5000,
+	10000,
+	20000,
+	20000,
+	20000,
+	20000
+};
+
 static ssize_t mma8452_show_samp_freq_avail(struct device *dev,
 				struct device_attribute *attr, char *buf)
 {
@@ -203,8 +221,7 @@ static int mma8452_read_raw(struct iio_dev *indio_dev,
 		*val2 = mma8452_scales[i][1];
 		return IIO_VAL_INT_PLUS_MICRO;
 	case IIO_CHAN_INFO_SAMP_FREQ:
-		i = (data->ctrl_reg1 & MMA8452_CTRL_DR_MASK) >>
-			MMA8452_CTRL_DR_SHIFT;
+		i = mma8452_get_odr_index(data);
 		*val = mma8452_samp_freq[i][0];
 		*val2 = mma8452_samp_freq[i][1];
 		return IIO_VAL_INT_PLUS_MICRO;
@@ -356,6 +373,54 @@ static int mma8452_write_event_config(struct iio_dev *indio_dev,
 	return mma8452_change_config(data, MMA8452_TRANSIENT_CFG, val);
 }
 
+static ssize_t mma8452_query_transient_period(struct device *dev,
+						struct device_attribute *attr,
+						char *buf)
+{
+	struct iio_dev *indio_dev = dev_to_iio_dev(dev);
+	struct mma8452_data *data = iio_priv(indio_dev);
+	int us, steps;
+
+	steps = i2c_smbus_read_byte_data(data->client, MMA8452_TRANSIENT_COUNT);
+	if (steps < 0)
+		return steps;
+
+	us = mma8452_transient_time_step_us[mma8452_get_odr_index(data)]
+								* steps;
+
+	return sprintf(buf, "%ld.%06ld\n",
+			us / USEC_PER_SEC, us % USEC_PER_SEC);
+}
+
+static ssize_t mma8452_set_transient_period(struct device *dev,
+						struct device_attribute *attr,
+						const char *buf,
+						size_t len)
+{
+	struct iio_dev *indio_dev = dev_to_iio_dev(dev);
+	struct mma8452_data *data = iio_priv(indio_dev);
+	int i, f, us, steps, ret;
+
+	ret = iio_str_to_fixpoint(buf, USEC_PER_SEC / 10, &i, &f);
+	if (ret)
+		return ret;
+	if (ret < 0)
+		return -EINVAL;
+
+	us = i * USEC_PER_SEC + f;
+	steps = us / mma8452_transient_time_step_us[
+				mma8452_get_odr_index(data)];
+
+	if (steps > 0xff)
+		return -EINVAL;
+
+	ret = mma8452_change_config(data, MMA8452_TRANSIENT_COUNT, steps);
+	if (ret)
+		return ret;
+
+	return len;
+}
+
 static void mma8452_push_transient_event(struct iio_dev *indio_dev,
 						int chan, u64 ts)
 {
@@ -462,8 +527,16 @@ static const struct iio_event_spec mma8452_transient_event[] = {
  */
 static IIO_CONST_ATTR_NAMED(accel_transient_scale, in_accel_scale, "0.617742");
 
+static IIO_DEVICE_ATTR_NAMED(accel_transient_period,
+			     in_accel_thresh_rising_period,
+			     S_IRUGO | S_IWUSR,
+			     mma8452_query_transient_period,
+			     mma8452_set_transient_period,
+			     0);
+
 static struct attribute *mma8452_event_attributes[] = {
 	&iio_const_attr_accel_transient_scale.dev_attr.attr,
+	&iio_dev_attr_accel_transient_period.dev_attr.attr,
 	NULL,
 };