ACPI: Reject below-freezing temperatures as invalid critical temperatures

My laptop thinks that it's a good idea to give -73C as the critical
CPU temperature.... which isn't the best thing since it causes a shutdown
right at bootup.

Temperatures below freezing are clearly invalid critical thresholds
so just reject these as such.

Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>
Acked-by: Zhang Rui <rui.zhang@intel.com>
Signed-off-by: Len Brown <len.brown@intel.com>

diff --git a/drivers/acpi/thermal.c b/drivers/acpi/thermal.c
index 504385b1f2116614bd8e53e598b5c093414b2841..84c795fb9b1ebef3a787907ba372cc368923a6c2 100644 (file)
--- a/drivers/acpi/thermal.c
+++ b/drivers/acpi/thermal.c
@@ -364,10 +364,17 @@ static int acpi_thermal_trips_update(struct acpi_thermal *tz, int flag)
        if (flag & ACPI_TRIPS_CRITICAL) {
                status = acpi_evaluate_integer(tz->device->handle,
                                "_CRT", NULL, &tz->trips.critical.temperature);
-               if (ACPI_FAILURE(status)) {
+               /*
+                * Treat freezing temperatures as invalid as well; some
+                * BIOSes return really low values and cause reboots at startup.
+                * Below zero (Celcius) values clearly aren't right for sure..
+                * ... so lets discard those as invalid.
+                */
+               if (ACPI_FAILURE(status) ||
+                               tz->trips.critical.temperature <= 2732) {
                        tz->trips.critical.flags.valid = 0;
                        ACPI_EXCEPTION((AE_INFO, status,
-                                       "No critical threshold"));
+                                       "No or invalid critical threshold"));
                        return -ENODEV;
                } else {
                        tz->trips.critical.flags.valid = 1;