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>

1 files changed, 9 insertions, 2 deletions

diff --git a/drivers/acpi/thermal.c b/drivers/acpi/thermal.c
index 504385b1f211..84c795fb9b1e 100644
--- 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;