ACPI: Adjust Kelvin offset to match local implementation

[mv-sheeva.git] / drivers / acpi / thermal.c

diff --git a/drivers/acpi/thermal.c b/drivers/acpi/thermal.c
index e8c143caf0fd6db6786944977c883af949ae84ca..ddbb7c8f994da7951261453f1f9ac4d95cdb4fc1 100644 (file)
--- a/drivers/acpi/thermal.c
+++ b/drivers/acpi/thermal.c
@@ -192,6 +192,7 @@ struct acpi_thermal {
        struct acpi_handle_list devices;
        struct thermal_zone_device *thermal_zone;
        int tz_enabled;
+       int kelvin_offset;
        struct mutex lock;
 };
 
@@ -581,7 +582,7 @@ static void acpi_thermal_check(void *data)
 }
 
 /* sys I/F for generic thermal sysfs support */
-#define KELVIN_TO_MILLICELSIUS(t) (t * 100 - 273200)
+#define KELVIN_TO_MILLICELSIUS(t, off) (((t) - (off)) * 100)
 
 static int thermal_get_temp(struct thermal_zone_device *thermal,
                            unsigned long *temp)
@@ -596,7 +597,7 @@ static int thermal_get_temp(struct thermal_zone_device *thermal,
        if (result)
                return result;
 
-       *temp = KELVIN_TO_MILLICELSIUS(tz->temperature);
+       *temp = KELVIN_TO_MILLICELSIUS(tz->temperature, tz->kelvin_offset);
        return 0;
 }
 
@@ -702,7 +703,8 @@ static int thermal_get_trip_temp(struct thermal_zone_device *thermal,
        if (tz->trips.critical.flags.valid) {
                if (!trip) {
                        *temp = KELVIN_TO_MILLICELSIUS(
-                               tz->trips.critical.temperature);
+                               tz->trips.critical.temperature,
+                               tz->kelvin_offset);
                        return 0;
                }
                trip--;
@@ -711,7 +713,8 @@ static int thermal_get_trip_temp(struct thermal_zone_device *thermal,
        if (tz->trips.hot.flags.valid) {
                if (!trip) {
                        *temp = KELVIN_TO_MILLICELSIUS(
-                               tz->trips.hot.temperature);
+                               tz->trips.hot.temperature,
+                               tz->kelvin_offset);
                        return 0;
                }
                trip--;
@@ -720,7 +723,8 @@ static int thermal_get_trip_temp(struct thermal_zone_device *thermal,
        if (tz->trips.passive.flags.valid) {
                if (!trip) {
                        *temp = KELVIN_TO_MILLICELSIUS(
-                               tz->trips.passive.temperature);
+                               tz->trips.passive.temperature,
+                               tz->kelvin_offset);
                        return 0;
                }
                trip--;
@@ -730,7 +734,8 @@ static int thermal_get_trip_temp(struct thermal_zone_device *thermal,
                tz->trips.active[i].flags.valid; i++) {
                if (!trip) {
                        *temp = KELVIN_TO_MILLICELSIUS(
-                               tz->trips.active[i].temperature);
+                               tz->trips.active[i].temperature,
+                               tz->kelvin_offset);
                        return 0;
                }
                trip--;
@@ -745,7 +750,8 @@ static int thermal_get_crit_temp(struct thermal_zone_device *thermal,
 
        if (tz->trips.critical.flags.valid) {
                *temperature = KELVIN_TO_MILLICELSIUS(
-                               tz->trips.critical.temperature);
+                               tz->trips.critical.temperature,
+                               tz->kelvin_offset);
                return 0;
        } else
                return -EINVAL;
@@ -1334,6 +1340,25 @@ static int acpi_thermal_get_info(struct acpi_thermal *tz)
        return 0;
 }
 
+/*
+ * The exact offset between Kelvin and degree Celsius is 273.15. However ACPI
+ * handles temperature values with a single decimal place. As a consequence,
+ * some implementations use an offset of 273.1 and others use an offset of
+ * 273.2. Try to find out which one is being used, to present the most
+ * accurate and visually appealing number.
+ *
+ * The heuristic below should work for all ACPI thermal zones which have a
+ * critical trip point with a value being a multiple of 0.5 degree Celsius.
+ */
+static void acpi_thermal_guess_offset(struct acpi_thermal *tz)
+{
+       if (tz->trips.critical.flags.valid &&
+           (tz->trips.critical.temperature % 5) == 1)
+               tz->kelvin_offset = 2731;
+       else
+               tz->kelvin_offset = 2732;
+}
+
 static int acpi_thermal_add(struct acpi_device *device)
 {
        int result = 0;
@@ -1360,6 +1385,8 @@ static int acpi_thermal_add(struct acpi_device *device)
        if (result)
                goto free_memory;
 
+       acpi_thermal_guess_offset(tz);
+
        result = acpi_thermal_register_thermal_zone(tz);
        if (result)
                goto free_memory;