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iio: adc: ad7124: add 3db filter 

This patch adds the LOW_PASS_FILTER_3DB_FREQUENCY attribute
in iio_chan_spec for each channel. The used filters are sinc3
or sinc4. The filter type with the highest output data rate
is used when setting a low pass frequency in the channel's sysfs.

Signed-off-by: Alexandru Tachici <alexandru.tachici@analog.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
This commit is contained in:
Alexandru Tachici 2020-01-22 10:54:14 +02:00 committed by Jonathan Cameron
parent ebf7a11267
commit cef2760954
1 changed files with 68 additions and 1 deletions
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69
drivers/iio/adc/ad7124.c
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@ -70,6 +70,11 @@
/* AD7124_FILTER_X */
#define AD7124_FILTER_FS_MSK GENMASK(10, 0)
#define AD7124_FILTER_FS(x) FIELD_PREP(AD7124_FILTER_FS_MSK, x)
#define AD7124_FILTER_TYPE_MSK GENMASK(23, 21)
#define AD7124_FILTER_TYPE_SEL(x) FIELD_PREP(AD7124_FILTER_TYPE_MSK, x)
#define AD7124_SINC3_FILTER 2
#define AD7124_SINC4_FILTER 0
enum ad7124_ids {
ID_AD7124_4,
@ -119,6 +124,7 @@ struct ad7124_channel_config {
unsigned int vref_mv;
unsigned int pga_bits;
unsigned int odr;
unsigned int filter_type;
};
struct ad7124_state {
@ -138,7 +144,8 @@ static const struct iio_chan_spec ad7124_channel_template = {
.info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |
BIT(IIO_CHAN_INFO_SCALE) |
BIT(IIO_CHAN_INFO_OFFSET) |
BIT(IIO_CHAN_INFO_SAMP_FREQ),
BIT(IIO_CHAN_INFO_SAMP_FREQ) |
BIT(IIO_CHAN_INFO_LOW_PASS_FILTER_3DB_FREQUENCY),
.scan_type = {
.sign = 'u',
.realbits = 24,
@ -281,6 +288,58 @@ static int ad7124_set_channel_gain(struct ad7124_state *st,
return 0;
}
static int ad7124_get_3db_filter_freq(struct ad7124_state *st,
unsigned int channel)
{
unsigned int fadc;
fadc = st->channel_config[channel].odr;
switch (st->channel_config[channel].filter_type) {
case AD7124_SINC3_FILTER:
return DIV_ROUND_CLOSEST(fadc * 230, 1000);
case AD7124_SINC4_FILTER:
return DIV_ROUND_CLOSEST(fadc * 262, 1000);
default:
return -EINVAL;
}
}
static int ad7124_set_3db_filter_freq(struct ad7124_state *st,
unsigned int channel,
unsigned int freq)
{
unsigned int sinc4_3db_odr;
unsigned int sinc3_3db_odr;
unsigned int new_filter;
unsigned int new_odr;
sinc4_3db_odr = DIV_ROUND_CLOSEST(freq * 1000, 230);
sinc3_3db_odr = DIV_ROUND_CLOSEST(freq * 1000, 262);
if (sinc4_3db_odr > sinc3_3db_odr) {
new_filter = AD7124_SINC3_FILTER;
new_odr = sinc4_3db_odr;
} else {
new_filter = AD7124_SINC4_FILTER;
new_odr = sinc3_3db_odr;
}
if (st->channel_config[channel].filter_type != new_filter) {
int ret;
st->channel_config[channel].filter_type = new_filter;
ret = ad7124_spi_write_mask(st, AD7124_FILTER(channel),
AD7124_FILTER_TYPE_MSK,
AD7124_FILTER_TYPE_SEL(new_filter),
3);
if (ret < 0)
return ret;
}
return ad7124_set_channel_odr(st, channel, new_odr);
}
static int ad7124_read_raw(struct iio_dev *indio_dev,
struct iio_chan_spec const *chan,
int *val, int *val2, long info)
@ -322,6 +381,9 @@ static int ad7124_read_raw(struct iio_dev *indio_dev,
case IIO_CHAN_INFO_SAMP_FREQ:
*val = st->channel_config[chan->address].odr;
return IIO_VAL_INT;
case IIO_CHAN_INFO_LOW_PASS_FILTER_3DB_FREQUENCY:
*val = ad7124_get_3db_filter_freq(st, chan->scan_index);
return IIO_VAL_INT;
default:
return -EINVAL;
@ -355,6 +417,11 @@ static int ad7124_write_raw(struct iio_dev *indio_dev,
gain = DIV_ROUND_CLOSEST(res, val2);
return ad7124_set_channel_gain(st, chan->address, gain);
case IIO_CHAN_INFO_LOW_PASS_FILTER_3DB_FREQUENCY:
if (val2 != 0)
return -EINVAL;
return ad7124_set_3db_filter_freq(st, chan->address, val);
default:
return -EINVAL;
}