thermal: ACPI: Invalidate trip points with temperature of 0 or below

It is reported that commit 950210887670 ("thermal: core: Drop
trips_disabled bitmask") causes the maximum frequency of CPUs to drop
further down with every system sleep-wake cycle on Intel Core i7-4710HQ.

This turns out to be due to a trip point whose temperature is equal to 0
degrees Celsius which is acted on every time the system wakes from sleep.

Before commit 950210887670 this trip point would be disabled wia the
trips_disabled bitmask, but now it is treated as a valid one.

Since ACPI thermal control is generally about protection against
overheating, trip points with temperature of 0 centigrade or below are
not particularly useful there, so initialize them all as invalid which
fixes the problem at hand.

Fixes: 950210887670 ("thermal: core: Drop trips_disabled bitmask")
Closes: https://lore.kernel.org/linux-pm/3f71747b-f852-4ee0-b384-cf46b2aefa3f@gmx.com
Reported-by: Tibor Billes <tbilles@gmx.com>
Tested-by: Tibor Billes <tbilles@gmx.com>
Cc: 6.7+ <stable@vger.kernel.org> # 6.7+
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

diff --git a/drivers/acpi/thermal.c b/drivers/acpi/thermal.c
index d67881b50bca28a1e08bb494b00c2bf0ee44957b..a0cfc857fb553efcaff8e66d4206aa7fd1a463d1 100644 (file)
--- a/drivers/acpi/thermal.c
+++ b/drivers/acpi/thermal.c
@@ -168,11 +168,17 @@ static int acpi_thermal_get_polling_frequency(struct acpi_thermal *tz)
 
 static int acpi_thermal_temp(struct acpi_thermal *tz, int temp_deci_k)
 {
+       int temp;
+
        if (temp_deci_k == THERMAL_TEMP_INVALID)
                return THERMAL_TEMP_INVALID;
 
-       return deci_kelvin_to_millicelsius_with_offset(temp_deci_k,
+       temp = deci_kelvin_to_millicelsius_with_offset(temp_deci_k,
                                                       tz->kelvin_offset);
+       if (temp <= 0)
+               return THERMAL_TEMP_INVALID;
+
+       return temp;
 }
 
 static bool acpi_thermal_trip_valid(struct acpi_thermal_trip *acpi_trip)