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

Petre Rodan
2025-09-10T07:58:13Z

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@subdimension.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