linux-kernel - [PATCH v2 12/14] iio: accel: bma220: add LPF cut-off frequency mapping

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Message-Id: <20250910-bma220_improvements-v2-12-e23f4f2b9745@subdimension.ro>
Date: Wed, 10 Sep 2025 10:57:17 +0300
From: Petre Rodan <petre.rodan@...dimension.ro>
To: Jonathan Cameron <jic23@...nel.org>, 
 David Lechner <dlechner@...libre.com>, 
 Nuno Sá <nuno.sa@...log.com>, 
 Andy Shevchenko <andy@...nel.org>, Rob Herring <robh@...nel.org>, 
 Krzysztof Kozlowski <krzk+dt@...nel.org>, 
 Conor Dooley <conor+dt@...nel.org>
Cc: Jonathan Cameron <Jonathan.Cameron@...wei.com>, 
 linux-iio@...r.kernel.org, devicetree@...r.kernel.org, 
 linux-kernel@...r.kernel.org, Petre Rodan <petre.rodan@...dimension.ro>
Subject: [PATCH v2 12/14] iio: accel: bma220: add LPF cut-off frequency
 mapping

Add mapping for the low pass filter cut-off frequency.
Make valid values visible for both the cut-off frequency and the scale.

Signed-off-by: Petre Rodan <petre.rodan@...dimension.ro>
---
ChangeLog:
- rename variables to include unit capitalization (dB, Hz)
---
 drivers/iio/accel/bma220_core.c | 61 ++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 60 insertions(+), 1 deletion(-)

diff --git a/drivers/iio/accel/bma220_core.c b/drivers/iio/accel/bma220_core.c
index 69bfd7f9f2b35e67835c6e1e41e02258e6741e7b..16a1aac5aa178ec06dc26e7e632f8ec5f43b5f78 100644
--- a/drivers/iio/accel/bma220_core.c
+++ b/drivers/iio/accel/bma220_core.c
@@ -95,13 +95,23 @@
 
 #define BMA220_DEVICE_NAME			"bma220"
 
+#define BMA220_COF_1000Hz			0x0
+#define BMA220_COF_500Hz			0x1
+#define BMA220_COF_250Hz			0x2
+#define BMA220_COF_125Hz			0x3
+#define BMA220_COF_64Hz				0x4
+#define BMA220_COF_32Hz				0x5
+
 #define BMA220_ACCEL_CHANNEL(index, reg, axis) {			\
 	.type = IIO_ACCEL,						\
 	.address = reg,							\
 	.modified = 1,							\
 	.channel2 = IIO_MOD_##axis,					\
 	.info_mask_separate = BIT(IIO_CHAN_INFO_RAW),			\
-	.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE),		\
+	.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE) |		\
+	    BIT(IIO_CHAN_INFO_LOW_PASS_FILTER_3DB_FREQUENCY),		\
+	.info_mask_shared_by_type_available = BIT(IIO_CHAN_INFO_SCALE) |\
+	    BIT(IIO_CHAN_INFO_LOW_PASS_FILTER_3DB_FREQUENCY),		\
 	.scan_index = index,						\
 	.scan_type = {							\
 		.sign = 's',						\
@@ -126,6 +136,7 @@ struct bma220_data {
 	struct device *dev;
 	struct regmap *regmap;
 	struct mutex lock;
+	u8 lpf_3dB_freq_idx;
 	u8 range_idx;
 	struct iio_trigger *trig;
 	struct {
@@ -142,6 +153,18 @@ static const struct iio_chan_spec bma220_channels[] = {
 	IIO_CHAN_SOFT_TIMESTAMP(3),
 };
 
+/*
+ * Available cut-off frequencies of the low pass filter in Hz.
+ */
+static const int bma220_lpf_3dB_freq_Hz_table[] = {
+	[BMA220_COF_1000Hz] = 1000,
+	[BMA220_COF_500Hz] = 500,
+	[BMA220_COF_250Hz] = 250,
+	[BMA220_COF_125Hz] = 125,
+	[BMA220_COF_64Hz] = 64,
+	[BMA220_COF_32Hz] = 32,
+};
+
 static const unsigned long bma220_accel_scan_masks[] = {
 	BIT(AXIS_X) | BIT(AXIS_Y) | BIT(AXIS_Z),
 	0
@@ -255,6 +278,10 @@ static int bma220_read_raw(struct iio_dev *indio_dev,
 		*val = bma220_scale_table[index][0];
 		*val2 = bma220_scale_table[index][1];
 		return IIO_VAL_INT_PLUS_MICRO;
+	case IIO_CHAN_INFO_LOW_PASS_FILTER_3DB_FREQUENCY:
+		index = data->lpf_3dB_freq_idx;
+		*val = bma220_lpf_3dB_freq_Hz_table[index];
+		return IIO_VAL_INT;
 	}
 
 	return -EINVAL;
@@ -273,6 +300,18 @@ static int bma220_find_match_2dt(const int (*tbl)[2], const int n,
 	return -EINVAL;
 }
 
+static int bma220_find_match(const int *arr, const int n, const int val)
+{
+	int i;
+
+	for (i = 0; i < n; i++) {
+		if (arr[i] == val)
+			return i;
+	}
+
+	return -EINVAL;
+}
+
 static int bma220_write_raw(struct iio_dev *indio_dev,
 			    struct iio_chan_spec const *chan,
 			    int val, int val2, long mask)
@@ -298,6 +337,21 @@ static int bma220_write_raw(struct iio_dev *indio_dev,
 			return ret;
 		data->range_idx = index;
 
+		return 0;
+	case IIO_CHAN_INFO_LOW_PASS_FILTER_3DB_FREQUENCY:
+		index = bma220_find_match(bma220_lpf_3dB_freq_Hz_table,
+					  ARRAY_SIZE(bma220_lpf_3dB_freq_Hz_table),
+					  val);
+		if (index < 0)
+			return -EINVAL;
+
+		ret = regmap_update_bits(data->regmap, BMA220_REG_FILTER,
+					 BMA220_FILTER_MASK,
+					 FIELD_PREP(BMA220_FILTER_MASK, index));
+		if (ret < 0)
+			return ret;
+		data->lpf_3dB_freq_idx = index;
+
 		return 0;
 	}
 
@@ -315,6 +369,11 @@ static int bma220_read_avail(struct iio_dev *indio_dev,
 		*type = IIO_VAL_INT_PLUS_MICRO;
 		*length = ARRAY_SIZE(bma220_scale_table) * 2;
 		return IIO_AVAIL_LIST;
+	case IIO_CHAN_INFO_LOW_PASS_FILTER_3DB_FREQUENCY:
+		*vals = (const int *)bma220_lpf_3dB_freq_Hz_table;
+		*type = IIO_VAL_INT;
+		*length = ARRAY_SIZE(bma220_lpf_3dB_freq_Hz_table);
+		return IIO_AVAIL_LIST;
 	default:
 		return -EINVAL;
 	}

-- 
2.49.1