diff --git a/drivers/thermal/thermal-generic-adc.c b/drivers/thermal/thermal-generic-adc.c
index 73f55d6a1721..ad601e5b4175 100644
--- a/drivers/thermal/thermal-generic-adc.c
+++ b/drivers/thermal/thermal-generic-adc.c
@@ -26,7 +26,7 @@ struct gadc_thermal_info {
 
 static int gadc_thermal_adc_to_temp(struct gadc_thermal_info *gti, int val)
 {
-	int temp, adc_hi, adc_lo;
+	int temp, temp_hi, temp_lo, adc_hi, adc_lo;
 	int i;
 
 	for (i = 0; i < gti->nlookup_table; i++) {
@@ -36,13 +36,17 @@ static int gadc_thermal_adc_to_temp(struct gadc_thermal_info *gti, int val)
 
 	if (i == 0) {
 		temp = gti->lookup_table[0];
-	} else if (i >= (gti->nlookup_table - 1)) {
+	} else if (i >= gti->nlookup_table) {
 		temp = gti->lookup_table[2 * (gti->nlookup_table - 1)];
 	} else {
 		adc_hi = gti->lookup_table[2 * i - 1];
 		adc_lo = gti->lookup_table[2 * i + 1];
-		temp = gti->lookup_table[2 * i];
-		temp -= ((val - adc_lo) * 1000) / (adc_hi - adc_lo);
+
+		temp_hi = gti->lookup_table[2 * i - 2];
+		temp_lo = gti->lookup_table[2 * i];
+
+		temp = temp_hi + mult_frac(temp_lo - temp_hi, val - adc_hi,
+					   adc_lo - adc_hi);
 	}
 
 	return temp;