[PATCH v4 08/14] iio: accel: adxl345: add freefall feature

[Lothar Rubusch <l.rubusch@gmail.com>]

Add the freefall detection of the sensor together with a threshold and
time parameter. A freefall event is detected if the measuring signal
falls below the threshold.

Introduce a freefall threshold stored in regmap cache, and a freefall
time, having the scaled time value stored as a member variable in the
state instance.

Signed-off-by: Lothar Rubusch <l.rubusch@gmail.com>
---
 drivers/iio/accel/adxl345_core.c | 122 +++++++++++++++++++++++++++++++
 1 file changed, 122 insertions(+)

diff --git a/drivers/iio/accel/adxl345_core.c b/drivers/iio/accel/adxl345_core.c
index 9e33236c786a..1a2bf0c630c9 100644
--- a/drivers/iio/accel/adxl345_core.c
+++ b/drivers/iio/accel/adxl345_core.c
@@ -78,6 +78,7 @@ struct adxl345_state {
 	u32 tap_duration_us;
 	u32 tap_latent_us;
 	u32 tap_window_us;
+	u32 ff_time_ms;
 
 	__le16 fifo_buf[ADXL345_DIRS * ADXL345_FIFO_SIZE + 1] __aligned(IIO_DMA_MINALIGN);
 };
@@ -99,6 +100,14 @@ static struct iio_event_spec adxl345_events[] = {
 			BIT(IIO_EV_INFO_RESET_TIMEOUT) |
 			BIT(IIO_EV_INFO_TAP2_MIN_DELAY),
 	},
+	{
+		/* free fall */
+		.type = IIO_EV_TYPE_MAG,
+		.dir = IIO_EV_DIR_FALLING,
+		.mask_shared_by_type = BIT(IIO_EV_INFO_ENABLE) |
+			BIT(IIO_EV_INFO_VALUE) |
+			BIT(IIO_EV_INFO_PERIOD),
+	},
 };
 
 #define ADXL345_CHANNEL(index, reg, axis) {					\
@@ -379,6 +388,64 @@ static int adxl345_set_tap_latent(struct adxl345_state *st, u32 val_int,
 	return _adxl345_set_tap_time(st, ADXL345_TAP_TIME_LATENT, val_fract_us);
 }
 
+/* freefall */
+
+static int adxl345_is_ff_en(struct adxl345_state *st, bool *en)
+{
+	int ret;
+	unsigned int regval;
+
+	ret = regmap_read(st->regmap, ADXL345_REG_INT_ENABLE, &regval);
+	if (ret)
+		return ret;
+
+	*en = FIELD_GET(ADXL345_INT_FREE_FALL, regval) > 0;
+
+	return 0;
+}
+
+static int adxl345_set_ff_en(struct adxl345_state *st, bool cmd_en)
+{
+	unsigned int regval, ff_threshold;
+	const unsigned int freefall_mask = 0x02;
+	bool en;
+	int ret;
+
+	ret = regmap_read(st->regmap, ADXL345_REG_THRESH_FF, &ff_threshold);
+	if (ret)
+		return ret;
+
+	en = cmd_en && ff_threshold > 0 && st->ff_time_ms > 0;
+
+	regval = en ? ADXL345_INT_FREE_FALL : 0x00;
+
+	return regmap_update_bits(st->regmap, ADXL345_REG_INT_ENABLE,
+				  freefall_mask, regval);
+}
+
+static int adxl345_set_ff_time(struct adxl345_state *st, u32 val_int,
+			       u32 val_fract_us)
+{
+	unsigned int regval;
+	int val_ms;
+
+	/*
+	 * max value is 255 * 5000 us = 1.275000 seconds
+	 *
+	 * Note: the scaling is similar to the scaling in the ADXL380
+	 */
+	if (1000000 * val_int + val_fract_us > 1275000)
+		return -EINVAL;
+
+	val_ms = val_int * 1000 + DIV_ROUND_UP(val_fract_us, 1000);
+	st->ff_time_ms = val_ms;
+
+	regval = DIV_ROUND_CLOSEST(val_ms, 5);
+
+	/* Values between 100ms and 350ms (0x14 to 0x46) are recommended. */
+	return regmap_write(st->regmap, ADXL345_REG_TIME_FF, min(regval, 0xff));
+}
+
 static int adxl345_read_raw(struct iio_dev *indio_dev,
 			    struct iio_chan_spec const *chan,
 			    int *val, int *val2, long mask)
@@ -491,6 +558,11 @@ static int adxl345_read_event_config(struct iio_dev *indio_dev,
 		default:
 			return -EINVAL;
 		}
+	case IIO_EV_TYPE_MAG:
+		ret = adxl345_is_ff_en(st, &int_en);
+		if (ret)
+			return ret;
+		return int_en;
 	default:
 		return -EINVAL;
 	}
@@ -514,6 +586,8 @@ static int adxl345_write_event_config(struct iio_dev *indio_dev,
 		default:
 			return -EINVAL;
 		}
+	case IIO_EV_TYPE_MAG:
+		return adxl345_set_ff_en(st, state);
 	default:
 		return -EINVAL;
 	}
@@ -528,6 +602,7 @@ static int adxl345_read_event_value(struct iio_dev *indio_dev,
 {
 	struct adxl345_state *st = iio_priv(indio_dev);
 	unsigned int tap_threshold;
+	unsigned int ff_threshold;
 	int ret;
 
 	switch (type) {
@@ -561,6 +636,22 @@ static int adxl345_read_event_value(struct iio_dev *indio_dev,
 		default:
 			return -EINVAL;
 		}
+	case IIO_EV_TYPE_MAG:
+		switch (info) {
+		case IIO_EV_INFO_VALUE:
+			ret = regmap_read(st->regmap, ADXL345_REG_THRESH_FF,
+					  &ff_threshold);
+			if (ret)
+				return ret;
+			*val = ff_threshold;
+			return IIO_VAL_INT;
+		case IIO_EV_INFO_PERIOD:
+			*val = st->ff_time_ms;
+			*val2 = 1000;
+			return IIO_VAL_FRACTIONAL;
+		default:
+			return -EINVAL;
+		}
 	default:
 		return -EINVAL;
 	}
@@ -601,6 +692,18 @@ static int adxl345_write_event_value(struct iio_dev *indio_dev,
 			break;
 		}
 		break;
+	case IIO_EV_TYPE_MAG:
+		switch (info) {
+		case IIO_EV_INFO_VALUE:
+			ret = regmap_write(st->regmap, ADXL345_REG_THRESH_FF, val);
+			break;
+		case IIO_EV_INFO_PERIOD:
+			ret = adxl345_set_ff_time(st, val, val2);
+			break;
+		default:
+			ret = -EINVAL;
+		}
+		break;
 	default:
 		ret = -EINVAL;
 		break;
@@ -862,6 +965,17 @@ static int adxl345_push_event(struct iio_dev *indio_dev, int int_stat,
 			return ret;
 	}
 
+	if (FIELD_GET(ADXL345_INT_FREE_FALL, int_stat)) {
+		ret = iio_push_event(indio_dev,
+				     IIO_MOD_EVENT_CODE(IIO_ACCEL, 0,
+							IIO_MOD_X_OR_Y_OR_Z,
+							IIO_EV_TYPE_MAG,
+							IIO_EV_DIR_FALLING),
+				     ts);
+		if (ret)
+			return ret;
+	}
+
 	if (FIELD_GET(ADXL345_INT_WATERMARK, int_stat)) {
 		samples = adxl345_get_samples(st);
 		if (samples < 0)
@@ -968,6 +1082,7 @@ int adxl345_core_probe(struct device *dev, struct regmap *regmap,
 					 ADXL345_DATA_FORMAT_FULL_RES |
 					 ADXL345_DATA_FORMAT_SELF_TEST);
 	unsigned int tap_threshold;
+	unsigned int ff_threshold;
 	int ret;
 
 	indio_dev = devm_iio_device_alloc(dev, sizeof(*st));
@@ -987,6 +1102,9 @@ int adxl345_core_probe(struct device *dev, struct regmap *regmap,
 	st->tap_window_us = 64;			/*   64 [0x40] -> .080    */
 	st->tap_latent_us = 16;			/*   16 [0x10] -> .020    */
 
+	ff_threshold = 8;			/*    8 [0x08]            */
+	st->ff_time_ms = 32;			/*   32 [0x20] -> 0.16    */
+
 	indio_dev->name = st->info->name;
 	indio_dev->info = &adxl345_info;
 	indio_dev->modes = INDIO_DIRECT_MODE;
@@ -1063,6 +1181,10 @@ int adxl345_core_probe(struct device *dev, struct regmap *regmap,
 		if (ret)
 			return ret;
 
+		ret = regmap_write(st->regmap, ADXL345_REG_THRESH_FF, ff_threshold);
+		if (ret)
+			return ret;
+
 		/* FIFO_STREAM mode is going to be activated later */
 		ret = devm_iio_kfifo_buffer_setup(dev, indio_dev, &adxl345_buffer_ops);
 		if (ret)
-- 
2.39.5