[PATCH] iio: imu: st_lsm6dsx: add hw timestamp support

[Lorenzo Bianconi <lorenzo.bianconi@redhat.com>]

Introduce hw timestamp support instead of compute sample timestamps
according to interrupt rate and configured watermark. LSM6DSx based
devices are able to queue in hw FIFO the time reference of data
sampling

Signed-off-by: Lorenzo Bianconi <lorenzo.bianconi@redhat.com>
---
 drivers/iio/imu/st_lsm6dsx/st_lsm6dsx.h        |  29 +++--
 drivers/iio/imu/st_lsm6dsx/st_lsm6dsx_buffer.c | 161 ++++++++++++++++---------
 drivers/iio/imu/st_lsm6dsx/st_lsm6dsx_core.c   | 104 +++++++++++++++-
 3 files changed, 224 insertions(+), 70 deletions(-)

diff --git a/drivers/iio/imu/st_lsm6dsx/st_lsm6dsx.h b/drivers/iio/imu/st_lsm6dsx/st_lsm6dsx.h
index 8fdd723afa05..a3cc7cd97026 100644
--- a/drivers/iio/imu/st_lsm6dsx/st_lsm6dsx.h
+++ b/drivers/iio/imu/st_lsm6dsx/st_lsm6dsx.h
@@ -27,7 +27,7 @@ enum st_lsm6dsx_hw_id {
 	ST_LSM6DSX_MAX_ID,
 };
 
-#define ST_LSM6DSX_BUFF_SIZE		256
+#define ST_LSM6DSX_BUFF_SIZE		400
 #define ST_LSM6DSX_CHAN_SIZE		2
 #define ST_LSM6DSX_SAMPLE_SIZE		6
 #define ST_LSM6DSX_MAX_WORD_LEN		((32 / ST_LSM6DSX_SAMPLE_SIZE) * \
@@ -57,6 +57,20 @@ struct st_lsm6dsx_fifo_ops {
 	u8 th_wl;
 };
 
+/**
+ * struct st_lsm6dsx_hw_ts_settings - ST IMU hw timer settings
+ * @timer_en: Hw timer enable register info (addr + mask).
+ * @hr_timer: Hw timer resolution register info (addr + mask).
+ * @fifo_en: Hw timer FIFO enable register info (addr + mask).
+ * @decimator: Hw timer FIFO decimator register info (addr + mask).
+ */
+struct st_lsm6dsx_hw_ts_settings {
+	struct st_lsm6dsx_reg timer_en;
+	struct st_lsm6dsx_reg hr_timer;
+	struct st_lsm6dsx_reg fifo_en;
+	struct st_lsm6dsx_reg decimator;
+};
+
 /**
  * struct st_lsm6dsx_settings - ST IMU sensor settings
  * @wai: Sensor WhoAmI default value.
@@ -64,6 +78,7 @@ struct st_lsm6dsx_fifo_ops {
  * @id: List of hw id supported by the driver configuration.
  * @decimator: List of decimator register info (addr + mask).
  * @fifo_ops: Sensor hw FIFO parameters.
+ * @ts_settings: Hw timer related settings.
  */
 struct st_lsm6dsx_settings {
 	u8 wai;
@@ -71,6 +86,7 @@ struct st_lsm6dsx_settings {
 	enum st_lsm6dsx_hw_id id[ST_LSM6DSX_MAX_ID];
 	struct st_lsm6dsx_reg decimator[ST_LSM6DSX_MAX_ID];
 	struct st_lsm6dsx_fifo_ops fifo_ops;
+	struct st_lsm6dsx_hw_ts_settings ts_settings;
 };
 
 enum st_lsm6dsx_sensor_id {
@@ -94,8 +110,7 @@ enum st_lsm6dsx_fifo_mode {
  * @watermark: Sensor watermark level.
  * @sip: Number of samples in a given pattern.
  * @decimator: FIFO decimation factor.
- * @delta_ts: Delta time between two consecutive interrupts.
- * @ts: Latest timestamp from the interrupt handler.
+ * @ts_ref: Sensor timestamp reference for hw one.
  */
 struct st_lsm6dsx_sensor {
 	char name[32];
@@ -108,9 +123,7 @@ struct st_lsm6dsx_sensor {
 	u16 watermark;
 	u8 sip;
 	u8 decimator;
-
-	s64 delta_ts;
-	s64 ts;
+	s64 ts_ref;
 };
 
 /**
@@ -122,7 +135,8 @@ struct st_lsm6dsx_sensor {
  * @conf_lock: Mutex to prevent concurrent FIFO configuration update.
  * @fifo_mode: FIFO operating mode supported by the device.
  * @enable_mask: Enabled sensor bitmask.
- * @sip: Total number of samples (acc/gyro) in a given pattern.
+ * @ts_sip: Total number of timestamp samples in a given pattern.
+ * @sip: Total number of samples (acc/gyro/ts) in a given pattern.
  * @buff: Device read buffer.
  * @iio_devs: Pointers to acc/gyro iio_dev instances.
  * @settings: Pointer to the specific sensor settings in use.
@@ -137,6 +151,7 @@ struct st_lsm6dsx_hw {
 
 	enum st_lsm6dsx_fifo_mode fifo_mode;
 	u8 enable_mask;
+	u8 ts_sip;
 	u8 sip;
 
 	u8 *buff;
diff --git a/drivers/iio/imu/st_lsm6dsx/st_lsm6dsx_buffer.c b/drivers/iio/imu/st_lsm6dsx/st_lsm6dsx_buffer.c
index 1d6aa9b1a4cf..1045e025e92b 100644
--- a/drivers/iio/imu/st_lsm6dsx/st_lsm6dsx_buffer.c
+++ b/drivers/iio/imu/st_lsm6dsx/st_lsm6dsx_buffer.c
@@ -46,9 +46,13 @@
 #define ST_LSM6DSX_FIFO_ODR_MASK		GENMASK(6, 3)
 #define ST_LSM6DSX_FIFO_EMPTY_MASK		BIT(12)
 #define ST_LSM6DSX_REG_FIFO_OUTL_ADDR		0x3e
+#define ST_LSM6DSX_REG_TS_RESET_ADDR		0x42
 
 #define ST_LSM6DSX_MAX_FIFO_ODR_VAL		0x08
 
+#define ST_LSM6DSX_TS_SENSITIVITY		25000UL /* 25us */
+#define ST_LSM6DSX_TS_RESET_VAL			0xaa
+
 struct st_lsm6dsx_decimator_entry {
 	u8 decimator;
 	u8 val;
@@ -98,9 +102,10 @@ static void st_lsm6dsx_get_max_min_odr(struct st_lsm6dsx_hw *hw,
 
 static int st_lsm6dsx_update_decimators(struct st_lsm6dsx_hw *hw)
 {
+	u16 max_odr, min_odr, sip = 0, ts_sip = 0;
+	const struct st_lsm6dsx_reg *ts_dec_reg;
 	struct st_lsm6dsx_sensor *sensor;
-	u16 max_odr, min_odr, sip = 0;
-	int err, i;
+	int err = 0, i;
 	u8 data;
 
 	st_lsm6dsx_get_max_min_odr(hw, &max_odr, &min_odr);
@@ -119,6 +124,7 @@ static int st_lsm6dsx_update_decimators(struct st_lsm6dsx_hw *hw)
 			sensor->decimator = 0;
 			data = 0;
 		}
+		ts_sip = max_t(u16, ts_sip, sensor->sip);
 
 		dec_reg = &hw->settings->decimator[sensor->id];
 		if (dec_reg->addr) {
@@ -131,9 +137,23 @@ static int st_lsm6dsx_update_decimators(struct st_lsm6dsx_hw *hw)
 		}
 		sip += sensor->sip;
 	}
-	hw->sip = sip;
+	hw->sip = sip + ts_sip;
+	hw->ts_sip = ts_sip;
 
-	return 0;
+	/*
+	 * update hw ts decimator if necessary. Decimator for hw timestamp
+	 * is always 1 or 0 in order to have a ts sample for each data
+	 * sample in FIFO
+	 */
+	ts_dec_reg = &hw->settings->ts_settings.decimator;
+	if (ts_dec_reg->addr) {
+		int val, ts_dec = !!hw->ts_sip;
+
+		val = ST_LSM6DSX_SHIFT_VAL(ts_dec, ts_dec_reg->mask);
+		err = regmap_update_bits(hw->regmap, ts_dec_reg->addr,
+					 ts_dec_reg->mask, val);
+	}
+	return err;
 }
 
 int st_lsm6dsx_set_fifo_mode(struct st_lsm6dsx_hw *hw,
@@ -208,6 +228,28 @@ int st_lsm6dsx_update_watermark(struct st_lsm6dsx_sensor *sensor, u16 watermark)
 				 &wdata, sizeof(wdata));
 }
 
+static int st_lsm6dsx_reset_hw_ts(struct st_lsm6dsx_hw *hw)
+{
+	struct st_lsm6dsx_sensor *sensor;
+	int i, err;
+
+	/* reset hw ts counter */
+	err = regmap_write(hw->regmap, ST_LSM6DSX_REG_TS_RESET_ADDR,
+			   ST_LSM6DSX_TS_RESET_VAL);
+	if (err < 0)
+		return err;
+
+	for (i = 0; i < ST_LSM6DSX_ID_MAX; i++) {
+		sensor = iio_priv(hw->iio_devs[i]);
+		/*
+		 * store enable buffer timestamp as reference for
+		 * hw timestamp
+		 */
+		sensor->ts_ref = iio_get_time_ns(hw->iio_devs[i]);
+	}
+	return 0;
+}
+
 /*
  * Set max bulk read to ST_LSM6DSX_MAX_WORD_LEN in order to avoid
  * a kmalloc for each bus access
@@ -231,6 +273,8 @@ static inline int st_lsm6dsx_read_block(struct st_lsm6dsx_hw *hw, u8 *data,
 	return 0;
 }
 
+#define ST_LSM6DSX_IIO_BUFF_SIZE	(ALIGN(ST_LSM6DSX_SAMPLE_SIZE, \
+					       sizeof(s64)) + sizeof(s64))
 /**
  * st_lsm6dsx_read_fifo() - LSM6DS3-LSM6DS3H-LSM6DSL-LSM6DSM read FIFO routine
  * @hw: Pointer to instance of struct st_lsm6dsx_hw.
@@ -243,11 +287,13 @@ static int st_lsm6dsx_read_fifo(struct st_lsm6dsx_hw *hw)
 {
 	u16 fifo_len, pattern_len = hw->sip * ST_LSM6DSX_SAMPLE_SIZE;
 	u16 fifo_diff_mask = hw->settings->fifo_ops.fifo_diff.mask;
-	int err, acc_sip, gyro_sip, read_len, samples, offset;
+	int err, acc_sip, gyro_sip, ts_sip, read_len, offset;
 	struct st_lsm6dsx_sensor *acc_sensor, *gyro_sensor;
-	s64 acc_ts, acc_delta_ts, gyro_ts, gyro_delta_ts;
-	u8 iio_buff[ALIGN(ST_LSM6DSX_SAMPLE_SIZE, sizeof(s64)) + sizeof(s64)];
+	u8 gyro_buff[ST_LSM6DSX_IIO_BUFF_SIZE];
+	u8 acc_buff[ST_LSM6DSX_IIO_BUFF_SIZE];
+	bool reset_ts = false;
 	__le16 fifo_status;
+	s64 ts = 0;
 
 	err = regmap_bulk_read(hw->regmap,
 			       hw->settings->fifo_ops.fifo_diff.addr,
@@ -260,23 +306,10 @@ static int st_lsm6dsx_read_fifo(struct st_lsm6dsx_hw *hw)
 
 	fifo_len = (le16_to_cpu(fifo_status) & fifo_diff_mask) *
 		   ST_LSM6DSX_CHAN_SIZE;
-	samples = fifo_len / ST_LSM6DSX_SAMPLE_SIZE;
 	fifo_len = (fifo_len / pattern_len) * pattern_len;
 
-	/*
-	 * compute delta timestamp between two consecutive samples
-	 * in order to estimate queueing time of data generated
-	 * by the sensor
-	 */
 	acc_sensor = iio_priv(hw->iio_devs[ST_LSM6DSX_ID_ACC]);
-	acc_ts = acc_sensor->ts - acc_sensor->delta_ts;
-	acc_delta_ts = div_s64(acc_sensor->delta_ts * acc_sensor->decimator,
-			       samples);
-
 	gyro_sensor = iio_priv(hw->iio_devs[ST_LSM6DSX_ID_GYRO]);
-	gyro_ts = gyro_sensor->ts - gyro_sensor->delta_ts;
-	gyro_delta_ts = div_s64(gyro_sensor->delta_ts * gyro_sensor->decimator,
-				samples);
 
 	for (read_len = 0; read_len < fifo_len; read_len += pattern_len) {
 		err = st_lsm6dsx_read_block(hw, hw->buff, pattern_len);
@@ -287,7 +320,7 @@ static int st_lsm6dsx_read_fifo(struct st_lsm6dsx_hw *hw)
 		 * Data are written to the FIFO with a specific pattern
 		 * depending on the configured ODRs. The first sequence of data
 		 * stored in FIFO contains the data of all enabled sensors
-		 * (e.g. Gx, Gy, Gz, Ax, Ay, Az), then data are repeated
+		 * (e.g. Gx, Gy, Gz, Ax, Ay, Az, Ts), then data are repeated
 		 * depending on the value of the decimation factor set for each
 		 * sensor.
 		 *
@@ -296,35 +329,65 @@ static int st_lsm6dsx_read_fifo(struct st_lsm6dsx_hw *hw)
 		 *   - gyroscope ODR = 208Hz, accelerometer ODR = 104Hz
 		 * Since the gyroscope ODR is twice the accelerometer one, the
 		 * following pattern is repeated every 9 samples:
-		 *   - Gx, Gy, Gz, Ax, Ay, Az, Gx, Gy, Gz
+		 *   - Gx, Gy, Gz, Ax, Ay, Az, Ts, Gx, Gy, Gz, Ts, Gx, ..
 		 */
 		gyro_sip = gyro_sensor->sip;
 		acc_sip = acc_sensor->sip;
+		ts_sip = hw->ts_sip;
 		offset = 0;
 
 		while (acc_sip > 0 || gyro_sip > 0) {
-			if (gyro_sip-- > 0) {
-				memcpy(iio_buff, &hw->buff[offset],
+			if (gyro_sip > 0) {
+				memcpy(gyro_buff, &hw->buff[offset],
 				       ST_LSM6DSX_SAMPLE_SIZE);
-				iio_push_to_buffers_with_timestamp(
-					hw->iio_devs[ST_LSM6DSX_ID_GYRO],
-					iio_buff, gyro_ts);
 				offset += ST_LSM6DSX_SAMPLE_SIZE;
-				gyro_ts += gyro_delta_ts;
 			}
-
-			if (acc_sip-- > 0) {
-				memcpy(iio_buff, &hw->buff[offset],
+			if (acc_sip > 0) {
+				memcpy(acc_buff, &hw->buff[offset],
 				       ST_LSM6DSX_SAMPLE_SIZE);
-				iio_push_to_buffers_with_timestamp(
-					hw->iio_devs[ST_LSM6DSX_ID_ACC],
-					iio_buff, acc_ts);
 				offset += ST_LSM6DSX_SAMPLE_SIZE;
-				acc_ts += acc_delta_ts;
 			}
+
+			if (ts_sip-- > 0) {
+				u8 data[ST_LSM6DSX_SAMPLE_SIZE];
+
+				memcpy(data, &hw->buff[offset], sizeof(data));
+				/*
+				 * hw timestamp is 3B long and it is stored
+				 * in FIFO using 6B as 4th FIFO data set
+				 * according to this schema:
+				 * B0 = ts[15:8], B1 = ts[23:16], B3 = ts[7:0]
+				 */
+				ts = data[1] << 16 | data[0] << 8 | data[3];
+				/*
+				 * check if hw timestamp engine is going to
+				 * reset (the sensor generates an interrupt
+				 * to signal the hw timestamp will reset in
+				 * 1.638s)
+				 */
+				if (!reset_ts && ts >= 0xff0000)
+					reset_ts = true;
+				ts *= ST_LSM6DSX_TS_SENSITIVITY;
+
+				offset += ST_LSM6DSX_SAMPLE_SIZE;
+			}
+
+			if (gyro_sip-- > 0)
+				iio_push_to_buffers_with_timestamp(
+					hw->iio_devs[ST_LSM6DSX_ID_GYRO],
+					gyro_buff, gyro_sensor->ts_ref + ts);
+			if (acc_sip-- > 0)
+				iio_push_to_buffers_with_timestamp(
+					hw->iio_devs[ST_LSM6DSX_ID_ACC],
+					acc_buff, acc_sensor->ts_ref + ts);
 		}
 	}
 
+	if (unlikely(reset_ts)) {
+		err = st_lsm6dsx_reset_hw_ts(hw);
+		if (err < 0)
+			return err;
+	}
 	return read_len;
 }
 
@@ -379,15 +442,12 @@ static int st_lsm6dsx_update_fifo(struct iio_dev *iio_dev, bool enable)
 		goto out;
 
 	if (hw->enable_mask) {
-		err = st_lsm6dsx_set_fifo_mode(hw, ST_LSM6DSX_FIFO_CONT);
+		/* reset hw ts counter */
+		err = st_lsm6dsx_reset_hw_ts(hw);
 		if (err < 0)
 			goto out;
 
-		/*
-		 * store enable buffer timestamp as reference to compute
-		 * first delta timestamp
-		 */
-		sensor->ts = iio_get_time_ns(iio_dev);
+		err = st_lsm6dsx_set_fifo_mode(hw, ST_LSM6DSX_FIFO_CONT);
 	}
 
 out:
@@ -399,25 +459,8 @@ static int st_lsm6dsx_update_fifo(struct iio_dev *iio_dev, bool enable)
 static irqreturn_t st_lsm6dsx_handler_irq(int irq, void *private)
 {
 	struct st_lsm6dsx_hw *hw = private;
-	struct st_lsm6dsx_sensor *sensor;
-	int i;
-
-	if (!hw->sip)
-		return IRQ_NONE;
-
-	for (i = 0; i < ST_LSM6DSX_ID_MAX; i++) {
-		sensor = iio_priv(hw->iio_devs[i]);
-
-		if (sensor->sip > 0) {
-			s64 timestamp;
-
-			timestamp = iio_get_time_ns(hw->iio_devs[i]);
-			sensor->delta_ts = timestamp - sensor->ts;
-			sensor->ts = timestamp;
-		}
-	}
 
-	return IRQ_WAKE_THREAD;
+	return hw->sip > 0 ? IRQ_WAKE_THREAD : IRQ_NONE;
 }
 
 static irqreturn_t st_lsm6dsx_handler_thread(int irq, void *private)
diff --git a/drivers/iio/imu/st_lsm6dsx/st_lsm6dsx_core.c b/drivers/iio/imu/st_lsm6dsx/st_lsm6dsx_core.c
index c2fa3239b9c6..8656d72ef4ee 100644
--- a/drivers/iio/imu/st_lsm6dsx/st_lsm6dsx_core.c
+++ b/drivers/iio/imu/st_lsm6dsx/st_lsm6dsx_core.c
@@ -181,6 +181,24 @@ static const struct st_lsm6dsx_settings st_lsm6dsx_sensor_settings[] = {
 			},
 			.th_wl = 3, /* 1LSB = 2B */
 		},
+		.ts_settings = {
+			.timer_en = {
+				.addr = 0x58,
+				.mask = BIT(7),
+			},
+			.hr_timer = {
+				.addr = 0x5c,
+				.mask = BIT(4),
+			},
+			.fifo_en = {
+				.addr = 0x07,
+				.mask = BIT(7),
+			},
+			.decimator = {
+				.addr = 0x09,
+				.mask = GENMASK(5, 3),
+			},
+		},
 	},
 	{
 		.wai = 0x69,
@@ -209,6 +227,24 @@ static const struct st_lsm6dsx_settings st_lsm6dsx_sensor_settings[] = {
 			},
 			.th_wl = 3, /* 1LSB = 2B */
 		},
+		.ts_settings = {
+			.timer_en = {
+				.addr = 0x58,
+				.mask = BIT(7),
+			},
+			.hr_timer = {
+				.addr = 0x5c,
+				.mask = BIT(4),
+			},
+			.fifo_en = {
+				.addr = 0x07,
+				.mask = BIT(7),
+			},
+			.decimator = {
+				.addr = 0x09,
+				.mask = GENMASK(5, 3),
+			},
+		},
 	},
 	{
 		.wai = 0x6a,
@@ -238,6 +274,24 @@ static const struct st_lsm6dsx_settings st_lsm6dsx_sensor_settings[] = {
 			},
 			.th_wl = 3, /* 1LSB = 2B */
 		},
+		.ts_settings = {
+			.timer_en = {
+				.addr = 0x19,
+				.mask = BIT(5),
+			},
+			.hr_timer = {
+				.addr = 0x5c,
+				.mask = BIT(4),
+			},
+			.fifo_en = {
+				.addr = 0x07,
+				.mask = BIT(7),
+			},
+			.decimator = {
+				.addr = 0x09,
+				.mask = GENMASK(5, 3),
+			},
+		},
 	},
 };
 
@@ -630,6 +684,44 @@ static int st_lsm6dsx_get_drdy_reg(struct st_lsm6dsx_hw *hw, u8 *drdy_reg)
 	return err;
 }
 
+static int st_lsm6dsx_init_hw_timer(struct st_lsm6dsx_hw *hw)
+{
+	const struct st_lsm6dsx_hw_ts_settings *ts_settings;
+	int err, val;
+
+	ts_settings = &hw->settings->ts_settings;
+	/* enable hw timestamp generation if necessary */
+	if (ts_settings->timer_en.addr) {
+		val = ST_LSM6DSX_SHIFT_VAL(1, ts_settings->timer_en.mask);
+		err = regmap_update_bits(hw->regmap,
+					 ts_settings->timer_en.addr,
+					 ts_settings->timer_en.mask, val);
+		if (err < 0)
+			return err;
+	}
+
+	/* enable high resolution for hw ts timer if necessary */
+	if (ts_settings->hr_timer.addr) {
+		val = ST_LSM6DSX_SHIFT_VAL(1, ts_settings->hr_timer.mask);
+		err = regmap_update_bits(hw->regmap,
+					 ts_settings->hr_timer.addr,
+					 ts_settings->hr_timer.mask, val);
+		if (err < 0)
+			return err;
+	}
+
+	/* enable ts queueing in FIFO if necessary */
+	if (ts_settings->fifo_en.addr) {
+		val = ST_LSM6DSX_SHIFT_VAL(1, ts_settings->fifo_en.mask);
+		err = regmap_update_bits(hw->regmap,
+					 ts_settings->fifo_en.addr,
+					 ts_settings->fifo_en.mask, val);
+		if (err < 0)
+			return err;
+	}
+	return 0;
+}
+
 static int st_lsm6dsx_init_device(struct st_lsm6dsx_hw *hw)
 {
 	u8 drdy_int_reg;
@@ -654,10 +746,14 @@ static int st_lsm6dsx_init_device(struct st_lsm6dsx_hw *hw)
 	if (err < 0)
 		return err;
 
-	return regmap_update_bits(hw->regmap, drdy_int_reg,
-				  ST_LSM6DSX_REG_FIFO_FTH_IRQ_MASK,
-				  FIELD_PREP(ST_LSM6DSX_REG_FIFO_FTH_IRQ_MASK,
-					     1));
+	err = regmap_update_bits(hw->regmap, drdy_int_reg,
+				 ST_LSM6DSX_REG_FIFO_FTH_IRQ_MASK,
+				 FIELD_PREP(ST_LSM6DSX_REG_FIFO_FTH_IRQ_MASK,
+					    1));
+	if (err < 0)
+		return err;
+
+	return st_lsm6dsx_init_hw_timer(hw);
 }
 
 static struct iio_dev *st_lsm6dsx_alloc_iiodev(struct st_lsm6dsx_hw *hw,
-- 
2.15.1