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iio: adc: ad7768-1: add low pass -3dB cutoff attribute

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Ad7768-1 has a different -3db frequency multiplier depending on
the filter type configured. The cutoff frequency also varies according
to the current ODR.

Add a readonly low pass -3dB frequency cutoff attribute to clarify to
the user which bandwidth is being allowed depending on the filter
configurations.

Reviewed-by: Marcelo Schmitt <marcelo.schmitt@analog.com>
Reviewed-by: David Lechner <dlechner@baylibre.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Jonathan Santos <Jonathan.Santos@analog.com>
Link: https://patch.msgid.link/804d66f1858014d7278aec3344d81c223661e878.1749569957.git.Jonathan.Santos@analog.com
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
This commit is contained in:
Jonathan Santos
2025-06-11 08:52:03 -03:00
committed by Jonathan Cameron
parent 5eef68d672
commit 00a468c931
1 changed files with 17 additions and 1 deletions
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18
drivers/iio/adc/ad7768-1.c
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@@ -22,6 +22,7 @@
#include <linux/sysfs.h>
#include <linux/spi/spi.h>
#include <linux/unaligned.h>
#include <linux/units.h>
#include <linux/util_macros.h>
#include <linux/iio/buffer.h>
@@ -152,6 +153,14 @@ enum ad7768_scan_type {
AD7768_SCAN_TYPE_HIGH_SPEED,
};
/* -3dB cutoff frequency multipliers (relative to ODR) for each filter type. */
static const int ad7768_filter_3db_odr_multiplier[] = {
[AD7768_FILTER_SINC5] = 204, /* 0.204 */
[AD7768_FILTER_SINC3] = 262, /* 0.2617 */
[AD7768_FILTER_SINC3_REJ60] = 262, /* 0.2617 */
[AD7768_FILTER_WIDEBAND] = 433, /* 0.433 */
};
static const int ad7768_mclk_div_rates[] = {
16, 8, 4, 2,
};
@@ -746,6 +755,7 @@ static const struct iio_chan_spec ad7768_channels[] = {
.type = IIO_VOLTAGE,
.info_mask_separate = BIT(IIO_CHAN_INFO_RAW),
.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE) |
BIT(IIO_CHAN_INFO_LOW_PASS_FILTER_3DB_FREQUENCY) |
BIT(IIO_CHAN_INFO_OVERSAMPLING_RATIO),
.info_mask_shared_by_type_available = BIT(IIO_CHAN_INFO_OVERSAMPLING_RATIO),
.info_mask_shared_by_all = BIT(IIO_CHAN_INFO_SAMP_FREQ),
@@ -766,7 +776,7 @@ static int ad7768_read_raw(struct iio_dev *indio_dev,
{
struct ad7768_state *st = iio_priv(indio_dev);
const struct iio_scan_type *scan_type;
int scale_uv, ret;
int scale_uv, ret, temp;
scan_type = iio_get_current_scan_type(indio_dev, chan);
if (IS_ERR(scan_type))
@@ -804,6 +814,12 @@ static int ad7768_read_raw(struct iio_dev *indio_dev,
case IIO_CHAN_INFO_OVERSAMPLING_RATIO:
*val = st->oversampling_ratio;
return IIO_VAL_INT;
case IIO_CHAN_INFO_LOW_PASS_FILTER_3DB_FREQUENCY:
temp = st->samp_freq * ad7768_filter_3db_odr_multiplier[st->filter_type];
*val = DIV_ROUND_CLOSEST(temp, MILLI);
return IIO_VAL_INT;
}