[PATCH v2 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.

Signed-off-by: Lothar Rubusch <l.rubusch@gmail.com>
---
 drivers/iio/accel/adxl345_core.c | 118 +++++++++++++++++++++++++++++++
 1 file changed, 118 insertions(+)

diff --git a/drivers/iio/accel/adxl345_core.c b/drivers/iio/accel/adxl345_core.c
index b6966fee3e3d..56c5a4d85d71 100644
--- a/drivers/iio/accel/adxl345_core.c
+++ b/drivers/iio/accel/adxl345_core.c
@@ -84,6 +84,9 @@ struct adxl345_state {
 	u32 tap_window_us;
 	bool tap_suppressed;
 
+	u8 ff_threshold;
+	u32 ff_time_ms;
+
 	__le16 fifo_buf[ADXL345_DIRS * ADXL345_FIFO_SIZE + 1] __aligned(IIO_DMA_MINALIGN);
 };
 
@@ -104,6 +107,14 @@ 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) {					\
@@ -354,6 +365,68 @@ 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);
 }
 
+/* ff */
+
+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, st->int_map) > 0;
+
+	return 0;
+}
+
+static int adxl345_set_ff_en(struct adxl345_state *st, bool cmd_en)
+{
+	bool en = cmd_en && st->ff_threshold > 0 && st->ff_time_ms > 0;
+
+	en ? __set_bit(ilog2(ADXL345_INT_FREE_FALL), (unsigned long *)&st->int_map)
+		: __clear_bit(ilog2(ADXL345_INT_FREE_FALL), (unsigned long *)&st->int_map);
+
+	return regmap_write(st->regmap, ADXL345_REG_INT_ENABLE, st->int_map);
+}
+
+static int adxl345_set_ff_threshold(struct adxl345_state *st, u8 val)
+{
+	int ret;
+
+	ret = regmap_write(st->regmap, ADXL345_REG_THRESH_FF, val);
+	if (ret)
+		return ret;
+
+	st->ff_threshold = val;
+
+	return 0;
+}
+
+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)
@@ -479,6 +552,11 @@ 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;
 	}
@@ -517,6 +595,8 @@ 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;
 	}
@@ -553,6 +633,18 @@ static int adxl345_read_event_value(struct iio_dev *indio_dev, const struct iio_
 		default:
 			return -EINVAL;
 		}
+	case IIO_EV_TYPE_MAG:
+		switch (info) {
+		case IIO_EV_INFO_VALUE:
+			*val = st->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;
 	}
@@ -591,6 +683,18 @@ static int adxl345_write_event_value(struct iio_dev *indio_dev,
 			ret = -EINVAL;
 		}
 		break;
+	case IIO_EV_TYPE_MAG:
+		switch (info) {
+		case IIO_EV_INFO_VALUE:
+			ret = adxl345_set_ff_threshold(st, val);
+			break;
+		case IIO_EV_INFO_PERIOD:
+			ret = adxl345_set_ff_time(st, val, val2);
+			break;
+		default:
+			ret = -EINVAL;
+		}
+		break;
 	default:
 		ret = -EINVAL;
 	}
@@ -934,6 +1038,17 @@ 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;
+	}
+
 	return -ENOENT;
 }
 
@@ -1041,6 +1156,9 @@ 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    */
 
+	st->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;
-- 
2.39.5