In sensor variants (such as ADXL380 and ADXL382) that support low-power
mode, the SAR signal path allows sampling acceleration data at lower rates;
more specifically, when the sensor operates in VLP mode, the sampling
frequency is 1 kHz.
To add support for the 1kHz sampling frequency value, modify the operating
mode selection logic to take into account the sampling frequency, and
configure the decimation filters only when applicable (i.e. when using a
sampling frequency that relies on the DSM signal path); in addition,
constrain the available sampling frequency values based on whether the
sensor is operating in low-power mode.

Signed-off-by: Francesco Lavra <flavra@baylibre.com>
---
 drivers/iio/accel/adxl380.c | 82 ++++++++++++++++++++++++++++---------
 drivers/iio/accel/adxl380.h | 10 ++++-
 2 files changed, 71 insertions(+), 21 deletions(-)

diff --git a/drivers/iio/accel/adxl380.c b/drivers/iio/accel/adxl380.c
index b99458a5eae3..7fe94e5cce0f 100644
--- a/drivers/iio/accel/adxl380.c
+++ b/drivers/iio/accel/adxl380.c
@@ -264,10 +264,12 @@ static int adxl380_set_measure_en(struct adxl380_state *st, bool en)
 
 		/*
 		 * Activity/Inactivity detection available only in VLP/ULP
-		 * mode and for devices that support low power modes. Otherwise
-		 * go straight to measure mode (same bits as ADXL380_OP_MODE_HP).
+		 * mode and for devices that support low power modes.
 		 */
 		if (act_inact_enabled)
+			st->odr = ADXL380_ODR_VLP;
+
+		if (st->odr == ADXL380_ODR_VLP)
 			op_mode = ADXL380_OP_MODE_VLP;
 		else
 			op_mode = ADXL380_OP_MODE_HP;
@@ -495,17 +497,22 @@ static int adxl380_set_odr(struct adxl380_state *st, u8 odr)
 	if (ret)
 		return ret;
 
-	ret = regmap_update_bits(st->regmap, ADXL380_TRIG_CFG_REG,
-				 ADXL380_TRIG_CFG_DEC_2X_MSK,
-				 FIELD_PREP(ADXL380_TRIG_CFG_DEC_2X_MSK, odr & 1));
-	if (ret)
-		return ret;
+	if (odr >= ADXL380_ODR_DSM) {
+		u8 mul = odr - ADXL380_ODR_DSM;
+		u8 field;
 
-	ret = regmap_update_bits(st->regmap, ADXL380_TRIG_CFG_REG,
-				 ADXL380_TRIG_CFG_SINC_RATE_MSK,
-				 FIELD_PREP(ADXL380_TRIG_CFG_SINC_RATE_MSK, odr >> 1));
-	if (ret)
-		return ret;
+		field = FIELD_PREP(ADXL380_TRIG_CFG_DEC_2X_MSK, mul & 1);
+		ret = regmap_update_bits(st->regmap, ADXL380_TRIG_CFG_REG,
+					 ADXL380_TRIG_CFG_DEC_2X_MSK, field);
+		if (ret)
+			return ret;
+
+		field = FIELD_PREP(ADXL380_TRIG_CFG_SINC_RATE_MSK, mul >> 1);
+		ret = regmap_update_bits(st->regmap, ADXL380_TRIG_CFG_REG,
+					 ADXL380_TRIG_CFG_SINC_RATE_MSK, field);
+		if (ret)
+			return ret;
+	}
 
 	st->odr = odr;
 	ret = adxl380_set_measure_en(st, true);
@@ -1145,6 +1152,31 @@ static const struct iio_buffer_setup_ops adxl380_buffer_ops = {
 	.predisable = adxl380_buffer_predisable,
 };
 
+static int adxl380_samp_freq_avail(struct adxl380_state *st, const int **vals,
+				   int *length)
+{
+	bool act_inact_enabled;
+	int ret;
+
+	if (!st->chip_info->has_low_power) {
+		*vals = st->chip_info->samp_freq_tbl + ADXL380_ODR_DSM;
+		*length = ADXL380_ODR_MAX - ADXL380_ODR_DSM;
+		return 0;
+	}
+
+	ret = adxl380_act_inact_enabled(st, &act_inact_enabled);
+	if (!ret) {
+		/*
+		 * Motion detection is only functional in low-power mode, and
+		 * this affects the available sampling frequencies.
+		 */
+		*vals = st->chip_info->samp_freq_tbl;
+		*length = act_inact_enabled ? ADXL380_ODR_DSM : ADXL380_ODR_MAX;
+	}
+
+	return ret;
+}
+
 static int adxl380_read_raw(struct iio_dev *indio_dev,
 			    struct iio_chan_spec const *chan,
 			    int *val, int *val2, long info)
@@ -1225,6 +1257,7 @@ static int adxl380_read_avail(struct iio_dev *indio_dev,
 			      long mask)
 {
 	struct adxl380_state *st = iio_priv(indio_dev);
+	int ret;
 
 	if (chan->type != IIO_ACCEL)
 		return -EINVAL;
@@ -1236,9 +1269,11 @@ static int adxl380_read_avail(struct iio_dev *indio_dev,
 		*length = ARRAY_SIZE(st->chip_info->scale_tbl) * 2;
 		return IIO_AVAIL_LIST;
 	case IIO_CHAN_INFO_SAMP_FREQ:
-		*vals = (const int *)st->chip_info->samp_freq_tbl;
+		ret = adxl380_samp_freq_avail(st, vals, length);
+		if (ret)
+			return ret;
+
 		*type = IIO_VAL_INT;
-		*length = ARRAY_SIZE(st->chip_info->samp_freq_tbl);
 		return IIO_AVAIL_LIST;
 	case IIO_CHAN_INFO_LOW_PASS_FILTER_3DB_FREQUENCY:
 		*vals = (const int *)st->lpf_tbl;
@@ -1261,12 +1296,18 @@ static int adxl380_write_raw(struct iio_dev *indio_dev,
 			     int val, int val2, long info)
 {
 	struct adxl380_state *st = iio_priv(indio_dev);
+	const int *freq_vals;
+	int freq_count;
 	int odr_index, lpf_index, hpf_index, range_index;
+	int ret;
 
 	switch (info) {
 	case IIO_CHAN_INFO_SAMP_FREQ:
-		odr_index = adxl380_find_match_1d_tbl(st->chip_info->samp_freq_tbl,
-						      ARRAY_SIZE(st->chip_info->samp_freq_tbl),
+		ret = adxl380_samp_freq_avail(st, &freq_vals, &freq_count);
+		if (ret)
+			return ret;
+
+		odr_index = adxl380_find_match_1d_tbl(freq_vals, freq_count,
 						      val);
 		return adxl380_set_odr(st, odr_index);
 	case IIO_CHAN_INFO_CALIBBIAS:
@@ -1628,7 +1669,7 @@ const struct adxl380_chip_info adxl318_chip_info = {
 		[ADXL380_OP_MODE_8G_RANGE] = { 0, 2615434 },
 		[ADXL380_OP_MODE_16G_RANGE] = { 0, 5229886 },
 	},
-	.samp_freq_tbl = { 8000, 16000, 32000 },
+	.samp_freq_tbl = { 0, 8000, 16000, 32000 },
 	/*
 	 * The datasheet defines an intercept of 550 LSB at 25 degC
 	 * and a sensitivity of 10.2 LSB/C.
@@ -1646,7 +1687,7 @@ const struct adxl380_chip_info adxl319_chip_info = {
 		[ADXL382_OP_MODE_30G_RANGE] = { 0, 9806650 },
 		[ADXL382_OP_MODE_60G_RANGE] = { 0, 19613300 },
 	},
-	.samp_freq_tbl = { 16000, 32000, 64000 },
+	.samp_freq_tbl = { 0, 16000, 32000, 64000 },
 	/*
 	 * The datasheet defines an intercept of 550 LSB at 25 degC
 	 * and a sensitivity of 10.2 LSB/C.
@@ -1664,7 +1705,7 @@ const struct adxl380_chip_info adxl380_chip_info = {
 		[ADXL380_OP_MODE_8G_RANGE] = { 0, 2615434 },
 		[ADXL380_OP_MODE_16G_RANGE] = { 0, 5229886 },
 	},
-	.samp_freq_tbl = { 8000, 16000, 32000 },
+	.samp_freq_tbl = { 1000, 8000, 16000, 32000 },
 	/*
 	 * The datasheet defines an intercept of 470 LSB at 25 degC
 	 * and a sensitivity of 10.2 LSB/C.
@@ -1684,7 +1725,7 @@ const struct adxl380_chip_info adxl382_chip_info = {
 		[ADXL382_OP_MODE_30G_RANGE] = { 0, 9806650 },
 		[ADXL382_OP_MODE_60G_RANGE] = { 0, 19613300 },
 	},
-	.samp_freq_tbl = { 16000, 32000, 64000 },
+	.samp_freq_tbl = { 1000, 16000, 32000, 64000 },
 	/*
 	 * The datasheet defines an intercept of 570 LSB at 25 degC
 	 * and a sensitivity of 10.2 LSB/C.
@@ -1923,6 +1964,7 @@ int adxl380_probe(struct device *dev, struct regmap *regmap,
 	st->dev = dev;
 	st->regmap = regmap;
 	st->chip_info = chip_info;
+	st->odr = ADXL380_ODR_DSM;
 
 	mutex_init(&st->lock);
 
diff --git a/drivers/iio/accel/adxl380.h b/drivers/iio/accel/adxl380.h
index e67c5aab8efc..d2c260c8b2fa 100644
--- a/drivers/iio/accel/adxl380.h
+++ b/drivers/iio/accel/adxl380.h
@@ -8,10 +8,18 @@
 #ifndef _ADXL380_H_
 #define _ADXL380_H_
 
+enum adxl380_odr {
+	ADXL380_ODR_VLP,
+	ADXL380_ODR_DSM,
+	ADXL380_ODR_DSM_2X,
+	ADXL380_ODR_DSM_4X,
+	ADXL380_ODR_MAX
+};
+
 struct adxl380_chip_info {
 	const char *name;
 	const int scale_tbl[3][2];
-	const int samp_freq_tbl[3];
+	const int samp_freq_tbl[ADXL380_ODR_MAX];
 	const struct iio_info *info;
 	const int temp_offset;
 	const u16 chip_id;
-- 
2.39.5

On Thu, 15 Jan 2026 18:53:50 +0100
Francesco Lavra <flavra@baylibre.com> wrote:

> In sensor variants (such as ADXL380 and ADXL382) that support low-power
> mode, the SAR signal path allows sampling acceleration data at lower rates;
> more specifically, when the sensor operates in VLP mode, the sampling
> frequency is 1 kHz.
> To add support for the 1kHz sampling frequency value, modify the operating
> mode selection logic to take into account the sampling frequency, and
> configure the decimation filters only when applicable (i.e. when using a
> sampling frequency that relies on the DSM signal path); in addition,
> constrain the available sampling frequency values based on whether the
> sensor is operating in low-power mode.
> 
> Signed-off-by: Francesco Lavra <flavra@baylibre.com>

Hi Francesco,

A similar case to the one Andy pointed out in the earlier patch plus
a trivial comment.  Given how trivial they are and where we are in the
cycle, I'll make them whilst applying.


Thanks,

Jonathan

>  
> +static int adxl380_samp_freq_avail(struct adxl380_state *st, const int **vals,
> +				   int *length)
> +{
> +	bool act_inact_enabled;
> +	int ret;
> +
> +	if (!st->chip_info->has_low_power) {
> +		*vals = st->chip_info->samp_freq_tbl + ADXL380_ODR_DSM;
> +		*length = ADXL380_ODR_MAX - ADXL380_ODR_DSM;
> +		return 0;
> +	}
> +
> +	ret = adxl380_act_inact_enabled(st, &act_inact_enabled);
> +	if (!ret) {
	if (ret)
		return ret;

	/*
	 * Motion detection is only functional in low-power mode, and this 
	 * affects the available sampling frequencies.
	 */
	*vals = st->chip_info->samp_freq_tbl;
	*length = act_inact_enabled ? ADXL380_ODR_DSM : ADXL380_ODR_MAX;

	return 0;
	
> +		/*
> +		 * Motion detection is only functional in low-power mode, and
> +		 * this affects the available sampling frequencies.
> +		 */
> +		*vals = st->chip_info->samp_freq_tbl;
> +		*length = act_inact_enabled ? ADXL380_ODR_DSM : ADXL380_ODR_MAX;
> +	}
> +
> +	return ret;
> +}

> @@ -1261,12 +1296,18 @@ static int adxl380_write_raw(struct iio_dev *indio_dev,
>  			     int val, int val2, long info)
>  {
>  	struct adxl380_state *st = iio_priv(indio_dev);
> +	const int *freq_vals;
> +	int freq_count;
>  	int odr_index, lpf_index, hpf_index, range_index;
> +	int ret;
Might as well combine the new variables on one line or even

  	int odr_index, lpf_index, hpf_index, range_index, freq_count, ret;