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path: root/drivers/acpi/thermal.c
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-rw-r--r--drivers/acpi/thermal.c41
1 files changed, 34 insertions, 7 deletions
diff --git a/drivers/acpi/thermal.c b/drivers/acpi/thermal.c
index e8c143caf0fd..ddbb7c8f994d 100644
--- 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;