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From: "Rafael J. Wysocki" <rjw@rjwysocki.net>
To: Linux PM <linux-pm@vger.kernel.org>
Cc: Tibor Billes <tbilles@gmx.com>, Doug Smythies <dsmythies@telus.net>,
 Linux ACPI <linux-acpi@vger.kernel.org>, LKML <linux-kernel@vger.kernel.org>,
 Daniel Lezcano <daniel.lezcano@linaro.org>,
 Lukasz Luba <lukasz.luba@arm.com>,
 Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>,
 Zhang Rui <rui.zhang@intel.com>
Subject:
 [PATCH v1] thermal: ACPI: Invalidate trip points with temperature of 0 or
 below
Date: Wed, 05 Jun 2024 21:15:10 +0200
Message-ID: <5784853.DvuYhMxLoT@kreacher>
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From: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

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>
---
 drivers/acpi/thermal.c |    8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

Index: linux-pm/drivers/acpi/thermal.c
===================================================================
--- linux-pm.orig/drivers/acpi/thermal.c
+++ linux-pm/drivers/acpi/thermal.c
@@ -168,11 +168,17 @@ static int acpi_thermal_get_polling_freq
 
 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)