From: Hoan Nguyen An <na-hoan@xxxxxxxxxxx>
About the formula for temperature calculation
[reg] = [temp] * a + b <=> [temp] = ([reg] - b) / a
Using "(mcelsius * tsc-> coef.aX) / 1000" instead of "DIV_ROUND_CLOSEST(mcelsius, 1000) * tsc-> coef.aX"
to avoid and reduce inaccuracy due to rounding the integer division.
Signed-off-by: Hoan Nguyen An <na-hoan@xxxxxxxxxxx>
---
drivers/thermal/rcar_gen3_thermal.c | 7 +++----
1 file changed, 3 insertions(+), 4 deletions(-)
diff --git a/drivers/thermal/rcar_gen3_thermal.c b/drivers/thermal/rcar_gen3_thermal.c
index 7aed533..dbb31b8 100644
--- a/drivers/thermal/rcar_gen3_thermal.c
+++ b/drivers/thermal/rcar_gen3_thermal.c
@@ -185,11 +185,10 @@ static int rcar_gen3_thermal_get_temp(void *devdata, int *temp)
static int rcar_gen3_thermal_mcelsius_to_temp(struct rcar_gen3_thermal_tsc *tsc,
int mcelsius)
{
- int celsius, val1, val2;
+ int val1, val2;
- celsius = DIV_ROUND_CLOSEST(mcelsius, 1000);
- val1 = celsius * tsc->coef.a1 + tsc->coef.b1;
- val2 = celsius * tsc->coef.a2 + tsc->coef.b2;
+ val1 = (mcelsius * tsc->coef.a1)/1000 + tsc->coef.b1;
+ val2 = (mcelsius * tsc->coef.a2)/1000 + tsc->coef.b2;
return INT_FIXPT((val1 + val2) / 2);
}
--
2.7.4
