[PATCH] iio: light: veml6075: fix UV index reported at half value

[Shardul Deshpande]

veml6075_get_uvi_micro() normalises the UV index for the configured
integration time by dividing the summed, responsivity-weighted UVA/UVB
components by the integration-time scale factor relative to the 50 ms
base case (which is returned undivided).

The supported integration times are 50, 100, 200, 400 and 800 ms, i.e.
the register field index int_index in 0..4 selects (50 << int_index) ms,
so the correct scale factor is 2^int_index == (1 << int_index).

The code instead divides by (2 << int_index) == 2^(int_index + 1), which
is twice the correct value. The reported UV index is therefore half of
the true value for every integration time except 50 ms (handled as a
separate case). As the driver powers up with VEML6075_IT_100_MS, the UV
index is reported at half value out of the box.

Divide by (1 << int_index) instead; this also matches the undivided
50 ms case (1 << 0 == 1).

Fixes: 3b82f43238ae ("iio: light: add VEML6075 UVA and UVB light sensor driver")
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Shardul Deshpande <iamsharduld@xxxxxxxxx>
---
 drivers/iio/light/veml6075.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/iio/light/veml6075.c b/drivers/iio/light/veml6075.c
index 59187244a..af71df69f 100644
--- a/drivers/iio/light/veml6075.c
+++ b/drivers/iio/light/veml6075.c
@@ -244,7 +244,7 @@ static int veml6075_get_uvi_micro(struct veml6075_data *data, int uva_comp,
 	case VEML6075_IT_200_MS:
 	case VEML6075_IT_400_MS:
 	case VEML6075_IT_800_MS:
-		return (uvia_micro + uvib_micro) / (2 << int_index);
+		return (uvia_micro + uvib_micro) / (1 << int_index);
 	default:
 		return -EINVAL;
 	}
-- 
2.50.1 (Apple Git-155)