1 files changed, 26 insertions, 13 deletions

diff --git a/drivers/thermal/imx_thermal.c b/drivers/thermal/imx_thermal.c
index 45af765a3198..a99c63152b8d 100644
--- a/drivers/thermal/imx_thermal.c
+++ b/drivers/thermal/imx_thermal.c
@@ -62,12 +62,16 @@ enum imx_thermal_trip {
 #define IMX_POLLING_DELAY               2000 /* millisecond */
 #define IMX_PASSIVE_DELAY               1000
 
+#define FACTOR0                         10000000
+#define FACTOR1                         15976
+#define FACTOR2                         4297157
+
 struct imx_thermal_data {
         struct thermal_zone_device *tz;
         struct thermal_cooling_device *cdev;
         enum thermal_device_mode mode;
         struct regmap *tempmon;
-        int c1, c2; /* See formula in imx_get_sensor_data() */
+        u32 c1, c2; /* See formula in imx_get_sensor_data() */
         unsigned long temp_passive;
         unsigned long temp_critical;
         unsigned long alarm_temp;
@@ -84,7 +88,7 @@ static void imx_set_alarm_temp(struct imx_thermal_data *data,
         int alarm_value;
 
         data->alarm_temp = alarm_temp;
-        alarm_value = (alarm_temp - data->c2) / data->c1;
+        alarm_value = (data->c2 - alarm_temp) / data->c1;
         regmap_write(map, TEMPSENSE0 + REG_CLR, TEMPSENSE0_ALARM_VALUE_MASK);
         regmap_write(map, TEMPSENSE0 + REG_SET, alarm_value <<
                         TEMPSENSE0_ALARM_VALUE_SHIFT);
@@ -136,7 +140,7 @@ static int imx_get_temp(struct thermal_zone_device *tz, unsigned long *temp)
         n_meas = (val & TEMPSENSE0_TEMP_CNT_MASK) >> TEMPSENSE0_TEMP_CNT_SHIFT;
 
         /* See imx_get_sensor_data() for formula derivation */
-        *temp = data->c2 + data->c1 * n_meas;
+        *temp = data->c2 - n_meas * data->c1;
 
         /* Update alarm value to next higher trip point */
         if (data->alarm_temp == data->temp_passive && *temp >= data->temp_passive)
@@ -305,6 +309,7 @@ static int imx_get_sensor_data(struct platform_device *pdev)
         int t1, t2, n1, n2;
         int ret;
         u32 val;
+        u64 temp64;
 
         map = syscon_regmap_lookup_by_phandle(pdev->dev.of_node,
                                               "fsl,tempmon-data");
@@ -330,6 +335,8 @@ static int imx_get_sensor_data(struct platform_device *pdev)
          *   [31:20] - sensor value @ 25C
          *    [19:8] - sensor value of hot
          *     [7:0] - hot temperature value
+         * Use universal formula now and only need sensor value @ 25C
+         * slope = 0.4297157 - (0.0015976 * 25C fuse)
          */
         n1 = val >> 20;
         n2 = (val & 0xfff00) >> 8;
@@ -337,20 +344,26 @@ static int imx_get_sensor_data(struct platform_device *pdev)
         t1 = 25; /* t1 always 25C */
 
         /*
-         * Derived from linear interpolation,
-         * Tmeas = T2 + (Nmeas - N2) * (T1 - T2) / (N1 - N2)
+         * Derived from linear interpolation:
+         * slope = 0.4297157 - (0.0015976 * 25C fuse)
+         * slope = (FACTOR2 - FACTOR1 * n1) / FACTOR0
+         * (Nmeas - n1) / (Tmeas - t1) = slope
          * We want to reduce this down to the minimum computation necessary
          * for each temperature read.  Also, we want Tmeas in millicelsius
          * and we don't want to lose precision from integer division. So...
-         * milli_Tmeas = 1000 * T2 + 1000 * (Nmeas - N2) * (T1 - T2) / (N1 - N2)
-         * Let constant c1 = 1000 * (T1 - T2) / (N1 - N2)
-         * milli_Tmeas = (1000 * T2) + c1 * (Nmeas - N2)
-         * milli_Tmeas = (1000 * T2) + (c1 * Nmeas) - (c1 * N2)
-         * Let constant c2 = (1000 * T2) - (c1 * N2)
-         * milli_Tmeas = c2 + (c1 * Nmeas)
+         * Tmeas = (Nmeas - n1) / slope + t1
+         * milli_Tmeas = 1000 * (Nmeas - n1) / slope + 1000 * t1
+         * milli_Tmeas = -1000 * (n1 - Nmeas) / slope + 1000 * t1
+         * Let constant c1 = (-1000 / slope)
+         * milli_Tmeas = (n1 - Nmeas) * c1 + 1000 * t1
+         * Let constant c2 = n1 *c1 + 1000 * t1
+         * milli_Tmeas = c2 - Nmeas * c1
          */
-        data->c1 = 1000 * (t1 - t2) / (n1 - n2);
-        data->c2 = 1000 * t2 - data->c1 * n2;
+        temp64 = FACTOR0;
+        temp64 *= 1000;
+        do_div(temp64, FACTOR1 * n1 - FACTOR2);
+        data->c1 = temp64;
+        data->c2 = n1 * data->c1 + 1000 * t1;
 
         /*
          * Set the default passive cooling trip point to 20 °C below the