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