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-rw-r--r--drivers/thermal/imx_thermal.c39
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