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>

diff --git a/drivers/iio/adc/ad7124.c b/drivers/iio/adc/ad7124.c
index d9915dc..f0206d8 100644 (file)
--- a/drivers/iio/adc/ad7124.c
+++ b/drivers/iio/adc/ad7124.c
@@ -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)
@@ -323,6 +382,9 @@ static int ad7124_read_raw(struct iio_dev *indio_dev,
                *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;
        }