linux-kernel - [PATCH 06/10] iio: accel: BMA220 add LPF cut-off frequency mapping

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Message-ID: <20250901194742.11599-7-petre.rodan@subdimension.ro>
Date: Mon,  1 Sep 2025 22:47:32 +0300
From: Petre Rodan <petre.rodan@...dimension.ro>
To: linux-iio@...r.kernel.org,
	linux-kernel@...r.kernel.org
Cc: Petre Rodan <petre.rodan@...dimension.ro>,
	Jonathan Cameron <jic23@...nel.org>,
	David Lechner <dlechner@...libre.com>,
	Nuno Sá <nuno.sa@...log.com>,
	Andy Shevchenko <andy@...nel.org>
Subject: [PATCH 06/10] 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>
---
 drivers/iio/accel/bma220_core.c | 60 ++++++++++++++++++++++++++++++++-
 1 file changed, 59 insertions(+), 1 deletion(-)

diff --git a/drivers/iio/accel/bma220_core.c b/drivers/iio/accel/bma220_core.c
index 86347cf8ab1e..e60acd62cf96 100644
--- a/drivers/iio/accel/bma220_core.c
+++ b/drivers/iio/accel/bma220_core.c
@@ -4,6 +4,15 @@
  *
  * Copyright (c) 2016,2020 Intel Corporation.
  * Copyright (c) 2025 Petre Rodan  <petre.rodan@...dimension.ro>
+ *
+ *
+ * Device register to IIO ABI mapping:
+ *
+ * Register                  | IIO ABI (sysfs)                | valid values
+ * --------------------------+--------------------------------+---------------
+ * scale (range)             | in_accel_scale                 | see _available
+ * cut-off freq (filt_config)| in_accel_filter_low_pass_...   | see _available
+ * ---------------------------------------------------------------------------
  */

 #include <linux/bits.h>
@@ -135,13 +144,23 @@

 #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',						\
@@ -172,6 +191,7 @@ 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 {
@@ -188,6 +208,18 @@ 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[][2] = {
+	[BMA220_COF_1000HZ] = {1000, 0},
+	[BMA220_COF_500HZ] = {500, 0},
+	[BMA220_COF_250HZ] = {250, 0},
+	[BMA220_COF_125HZ] = {125, 0},
+	[BMA220_COF_64HZ] = {64, 0},
+	[BMA220_COF_32HZ] = {32, 0},
+};
+
 static const unsigned long bma220_accel_scan_masks[] = {
 	BIT(AXIS_X) | BIT(AXIS_Y) | BIT(AXIS_Z),
 	0
@@ -309,6 +341,11 @@ 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][0];
+		*val2 = bma220_lpf_3db_freq_hz_table[index][1];
+		return IIO_VAL_INT_PLUS_MICRO;
 	}

 	return -EINVAL;
@@ -353,6 +390,22 @@ static int bma220_write_raw(struct iio_dev *indio_dev,
 				"failed to set measurement range\n");
 		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, val2);
+		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)
+			dev_err(data->dev,
+				"failed to set low pass filter\n");
+		data->lpf_3db_freq_idx = index;
+
 		return 0;
 	}

@@ -370,6 +423,11 @@ 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_PLUS_MICRO;
+		*length = ARRAY_SIZE(bma220_lpf_3db_freq_hz_table) * 2;
+		return IIO_AVAIL_LIST;
 	default:
 		return -EINVAL;
 	}
--
2.49.1