hwmon: (sht15) Fix sht15_calc_temp interpolation function

I discovered two issues.
First the previous sht15_calc_temp() loop did not iterate through the
temppoints array since the (data->supply_uV > temppoints[i - 1].vdd)
test is always true in this direction.

Also the two-points linear interpolation function was returning biased
values due to a stray division by 1000 which shouldn't be there.

[JD: Also change the default value for d1 from 0 to something saner.]

Signed-off-by: Jerome Oufella <jerome.oufella@savoirfairelinux.com>
Acked-by: Jonathan Cameron <jic23@cam.ac.uk>
Signed-off-by: Jean Delvare <khali@linux-fr.org>
Cc: stable@kernel.org

1 files changed, 3 insertions, 3 deletions

diff --git a/drivers/hwmon/sht15.c b/drivers/hwmon/sht15.c
index 6b2d8ae64fe1..9a15b1af1f11 100644
--- a/drivers/hwmon/sht15.c
+++ b/drivers/hwmon/sht15.c
@@ -303,13 +303,13 @@ error_ret:
  **/
 static inline int sht15_calc_temp(struct sht15_data *data)
 {
-        int d1 = 0;
+        int d1 = temppoints[0].d1;
         int i;
 
-        for (i = 1; i < ARRAY_SIZE(temppoints); i++)
+        for (i = ARRAY_SIZE(temppoints) - 1; i > 0; i--)
                 /* Find pointer to interpolate */
                 if (data->supply_uV > temppoints[i - 1].vdd) {
-                        d1 = (data->supply_uV/1000 - temppoints[i - 1].vdd)
+                        d1 = (data->supply_uV - temppoints[i - 1].vdd)
                                 * (temppoints[i].d1 - temppoints[i - 1].d1)
                                 / (temppoints[i].vdd - temppoints[i - 1].vdd)
                                 + temppoints[i - 1].d1;