iio:ad7791: Report scale as fractional value

Move the complexity of calculating the fixed point scale to the core.

Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

1 files changed, 10 insertions, 8 deletions

diff --git a/drivers/iio/adc/ad7791.c b/drivers/iio/adc/ad7791.c
index c20203577d2d..c19f8fd1b4b7 100644
--- a/drivers/iio/adc/ad7791.c
+++ b/drivers/iio/adc/ad7791.c
@@ -202,7 +202,6 @@ static int ad7791_read_raw(struct iio_dev *indio_dev,
 {
         struct ad7791_state *st = iio_priv(indio_dev);
         bool unipolar = !!(st->mode & AD7791_MODE_UNIPOLAR);
-        unsigned long long scale_pv;
 
         switch (info) {
         case IIO_CHAN_INFO_RAW:
@@ -220,23 +219,26 @@ static int ad7791_read_raw(struct iio_dev *indio_dev,
         case IIO_CHAN_INFO_SCALE:
                 /* The monitor channel uses an internal reference. */
                 if (chan->address == AD7791_CH_AVDD_MONITOR) {
-                        scale_pv = 5850000000000ULL;
+                        /*
+                         * The signal is attenuated by a factor of 5 and
+                         * compared against a 1.17V internal reference.
+                         */
+                        *val = 1170 * 5;
                 } else {
                         int voltage_uv;
 
                         voltage_uv = regulator_get_voltage(st->reg);
                         if (voltage_uv < 0)
                                 return voltage_uv;
-                        scale_pv = (unsigned long long)voltage_uv * 1000000;
+
+                        *val = voltage_uv / 1000;
                 }
                 if (unipolar)
-                        scale_pv >>= chan->scan_type.realbits;
+                        *val2 = chan->scan_type.realbits;
                 else
-                        scale_pv >>= chan->scan_type.realbits - 1;
-                *val2 = do_div(scale_pv, 1000000000);
-                *val = scale_pv;
+                        *val2 = chan->scan_type.realbits - 1;
 
-                return IIO_VAL_INT_PLUS_NANO;
+                return IIO_VAL_FRACTIONAL_LOG2;
         }
 
         return -EINVAL;