drivers: sensor: lsm6dso: Add support for Accel LP filter

Add device tree support for enabling the second low pass filter
(LPF2) for the accelerometer output.

This adds additional low pass on top of the default ODR/2 from
the LPF1 output.

Signed-off-by: Emil Hammarström <[email protected]>

Author: eHammarstrom

drivers/sensor/st/lsm6dso/lsm6dso.c

@@ -22,6 +22,14 @@ LOG_MODULE_REGISTER(LSM6DSO, CONFIG_SENSOR_LOG_LEVEL);
 
 static const uint16_t lsm6dso_odr_map[] = {0, 12, 26, 52, 104, 208, 417, 833,
 					1667, 3333, 6667};
+static const uint8_t lsm6dso_lp_filter_map[] = {0,
+						LSM6DSO_LP_ODR_DIV_10,
+						LSM6DSO_LP_ODR_DIV_20,
+						LSM6DSO_LP_ODR_DIV_45,
+						LSM6DSO_LP_ODR_DIV_100,
+						LSM6DSO_LP_ODR_DIV_200,
+						LSM6DSO_LP_ODR_DIV_400,
+						LSM6DSO_LP_ODR_DIV_800};
 
 static int lsm6dso_freq_to_odr_val(uint16_t freq)
 {
@@ -813,6 +821,19 @@ static int lsm6dso_init_chip(const struct device *dev)
 		return -EIO;
 	}
 
+	if (cfg->accel_lp_filter) {
+		if (lsm6dso_xl_filter_lp2_set(ctx, 1)) {
+			LOG_ERR("failed to enable low pass filter (LPF2)");
+			return -EIO;
+		}
+
+		if (lsm6dso_xl_hp_path_on_out_set(ctx,
+				lsm6dso_lp_filter_map[cfg->accel_lp_filter])) {
+			LOG_ERR("failed to configure low pass filter (LPF2)");
+			return -EIO;
+		}
+	}
+
 	return 0;
 }
 
@@ -898,6 +919,7 @@ static int lsm6dso_init(const struct device *dev)
 #define LSM6DSO_CONFIG_COMMON(inst)					\
 	.accel_pm = DT_INST_PROP(inst, accel_pm),			\
 	.accel_odr = DT_INST_PROP(inst, accel_odr),			\
+	.accel_lp_filter = DT_INST_PROP(inst, accel_lp_filter),		\
 	.accel_range = DT_INST_PROP(inst, accel_range) |		\
 		(DT_INST_NODE_HAS_COMPAT(inst, st_lsm6dso32) ?	        \
 			ACCEL_RANGE_DOUBLE : 0),			\

drivers/sensor/st/lsm6dso/lsm6dso.h

@@ -52,6 +52,7 @@ struct lsm6dso_config {
 	} stmemsc_cfg;
 	uint8_t accel_pm;
 	uint8_t accel_odr;
+	uint8_t accel_lp_filter;
 #define ACCEL_RANGE_DOUBLE	BIT(7)
 #define ACCEL_RANGE_MASK	BIT_MASK(6)
 	uint8_t accel_range;

dts/bindings/sensor/st,lsm6dso-common.yaml

@@ -94,6 +94,25 @@ properties:
 
     enum: [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11]
 
+  accel-lp-filter:
+    type: int
+    default: 0
+    description: |
+      Specify the amount of low pass filtering applied to the accelerometer values.
+      Default is power-up configuration.
+      This will enable the LPF2 lowpass filter via the lpf2_xl_en bit in the CTRL1_XL register.
+
+      - 0 # LSM6DSO_DT_LP_ODR_DIV_2
+      - 1 # LSM6DSO_DT_LP_ODR_DIV_10
+      - 2 # LSM6DSO_DT_LP_ODR_DIV_20
+      - 3 # LSM6DSO_DT_LP_ODR_DIV_45
+      - 4 # LSM6DSO_DT_LP_ODR_DIV_100
+      - 5 # LSM6DSO_DT_LP_ODR_DIV_200
+      - 6 # LSM6DSO_DT_LP_ODR_DIV_400
+      - 7 # LSM6DSO_DT_LP_ODR_DIV_800
+
+    enum: [0, 1, 2, 3, 4, 5, 6, 7]
+
   gyro-pm:
     type: int
     default: 0

include/zephyr/dt-bindings/sensor/lsm6dso.h

@@ -42,6 +42,16 @@
 #define LSM6DSO_DT_ODR_6667Hz			0xa
 #define LSM6DSO_DT_ODR_1Hz6			0xb
 
+/* Low pass filter dividers */
+#define LSM6DSO_DT_LP_ODR_DIV_2			0
+#define LSM6DSO_DT_LP_ODR_DIV_10		1
+#define LSM6DSO_DT_LP_ODR_DIV_20		2
+#define LSM6DSO_DT_LP_ODR_DIV_45		3
+#define LSM6DSO_DT_LP_ODR_DIV_100		4
+#define LSM6DSO_DT_LP_ODR_DIV_200		5
+#define LSM6DSO_DT_LP_ODR_DIV_400		6
+#define LSM6DSO_DT_LP_ODR_DIV_800		7
+
 /* Tap mode */
 #define LSM6DSO_DT_SINGLE_TAP			0
 #define LSM6DSO_DT_SINGLE_DOUBLE_TAP		1