thermal: ACPI: Add ACPI trip point routines

Add library routines to populate a generic thermal trip point
structure with data obtained by evaluating a specific object in the
ACPI Namespace.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Co-developed-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Tested-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>

drivers/thermal/Kconfig

@@ -76,6 +76,10 @@ config THERMAL_OF
 	  Say 'Y' here if you need to build thermal infrastructure
 	  based on device tree.
 
+config THERMAL_ACPI
+       depends on ACPI
+       bool
+
 config THERMAL_WRITABLE_TRIPS
 	bool "Enable writable trip points"
 	help

drivers/thermal/Makefile

@@ -13,6 +13,7 @@ thermal_sys-$(CONFIG_THERMAL_NETLINK)		+= thermal_netlink.o
 # interface to/from other layers providing sensors
 thermal_sys-$(CONFIG_THERMAL_HWMON)		+= thermal_hwmon.o
 thermal_sys-$(CONFIG_THERMAL_OF)		+= thermal_of.o
+thermal_sys-$(CONFIG_THERMAL_ACPI)		+= thermal_acpi.o
 
 # governors
 thermal_sys-$(CONFIG_THERMAL_GOV_FAIR_SHARE)	+= gov_fair_share.o

drivers/thermal/thermal_acpi.c

@@ -0,0 +1,150 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright 2023 Linaro Limited
+ * Copyright 2023 Intel Corporation
+ *
+ * Library routines for populating a generic thermal trip point structure
+ * with data obtained by evaluating a specific object in the ACPI Namespace.
+ */
+#include <linux/acpi.h>
+#include <linux/units.h>
+
+#include "thermal_core.h"
+
+/*
+ * Minimum temperature for full military grade is 218°K (-55°C) and
+ * max temperature is 448°K (175°C). We can consider those values as
+ * the boundaries for the [trips] temperature returned by the
+ * firmware. Any values out of these boundaries may be considered
+ * bogus and we can assume the firmware has no data to provide.
+ */
+#define TEMP_MIN_DECIK	2180
+#define TEMP_MAX_DECIK	4480
+
+static int thermal_acpi_trip_init(struct acpi_device *adev,
+				  enum thermal_trip_type type, int id,
+				  struct thermal_trip *trip)
+{
+	unsigned long long temp;
+	acpi_status status;
+	char obj_name[5];
+
+	switch (type) {
+	case THERMAL_TRIP_ACTIVE:
+		if (id < 0 || id > 9)
+			return -EINVAL;
+
+		obj_name[1] = 'A';
+		obj_name[2] = 'C';
+		obj_name[3] = '0' + id;
+		break;
+	case THERMAL_TRIP_PASSIVE:
+		obj_name[1] = 'P';
+		obj_name[2] = 'S';
+		obj_name[3] = 'V';
+		break;
+	case THERMAL_TRIP_HOT:
+		obj_name[1] = 'H';
+		obj_name[2] = 'O';
+		obj_name[3] = 'T';
+		break;
+	case THERMAL_TRIP_CRITICAL:
+		obj_name[1] = 'C';
+		obj_name[2] = 'R';
+		obj_name[3] = 'T';
+		break;
+	}
+
+	obj_name[0] = '_';
+	obj_name[4] = '\0';
+
+	status = acpi_evaluate_integer(adev->handle, obj_name, NULL, &temp);
+	if (ACPI_FAILURE(status)) {
+		acpi_handle_debug(adev->handle, "%s evaluation failed\n", obj_name);
+		return -ENODATA;
+	}
+
+	if (temp < TEMP_MIN_DECIK || temp >= TEMP_MAX_DECIK) {
+		acpi_handle_debug(adev->handle, "%s result %llu out of range\n",
+				  obj_name, temp);
+		return -ENODATA;
+	}
+
+	trip->temperature = deci_kelvin_to_millicelsius(temp);
+	trip->hysteresis = 0;
+	trip->type = type;
+
+	return 0;
+}
+
+/**
+ * thermal_acpi_trip_active - Get the specified active trip point
+ * @adev: Thermal zone ACPI device object to get the description from.
+ * @id: Active cooling level (0 - 9).
+ * @trip: Trip point structure to be populated on success.
+ *
+ * Evaluate the _ACx object for the thermal zone represented by @adev to obtain
+ * the temperature of the active cooling trip point corresponding to the active
+ * cooling level given by @id and initialize @trip as an active trip point using
+ * that temperature value.
+ *
+ * Return 0 on success or a negative error value on failure.
+ */
+int thermal_acpi_trip_active(struct acpi_device *adev, int id,
+			     struct thermal_trip *trip)
+{
+	return thermal_acpi_trip_init(adev, THERMAL_TRIP_ACTIVE, id, trip);
+}
+EXPORT_SYMBOL_GPL(thermal_acpi_trip_active);
+
+/**
+ * thermal_acpi_trip_passive - Get the passive trip point
+ * @adev: Thermal zone ACPI device object to get the description from.
+ * @trip: Trip point structure to be populated on success.
+ *
+ * Evaluate the _PSV object for the thermal zone represented by @adev to obtain
+ * the temperature of the passive cooling trip point and initialize @trip as a
+ * passive trip point using that temperature value.
+ *
+ * Return 0 on success or -ENODATA on failure.
+ */
+int thermal_acpi_trip_passive(struct acpi_device *adev, struct thermal_trip *trip)
+{
+	return thermal_acpi_trip_init(adev, THERMAL_TRIP_PASSIVE, INT_MAX, trip);
+}
+EXPORT_SYMBOL_GPL(thermal_acpi_trip_passive);
+
+/**
+ * thermal_acpi_trip_hot - Get the near critical trip point
+ * @adev: the ACPI device to get the description from.
+ * @trip: a &struct thermal_trip to be filled if the function succeed.
+ *
+ * Evaluate the _HOT object for the thermal zone represented by @adev to obtain
+ * the temperature of the trip point at which the system is expected to be put
+ * into the S4 sleep state and initialize @trip as a hot trip point using that
+ * temperature value.
+ *
+ * Return 0 on success or -ENODATA on failure.
+ */
+int thermal_acpi_trip_hot(struct acpi_device *adev, struct thermal_trip *trip)
+{
+	return thermal_acpi_trip_init(adev, THERMAL_TRIP_HOT, INT_MAX, trip);
+}
+EXPORT_SYMBOL_GPL(thermal_acpi_trip_hot);
+
+/**
+ * thermal_acpi_trip_critical - Get the critical trip point
+ * @adev: the ACPI device to get the description from.
+ * @trip: a &struct thermal_trip to be filled if the function succeed.
+ *
+ * Evaluate the _CRT object for the thermal zone represented by @adev to obtain
+ * the temperature of the critical cooling trip point and initialize @trip as a
+ * critical trip point using that temperature value.
+ *
+ * Return 0 on success or -ENODATA on failure.
+ */
+int thermal_acpi_trip_critical(struct acpi_device *adev, struct thermal_trip *trip)
+{
+	return thermal_acpi_trip_init(adev, THERMAL_TRIP_CRITICAL, INT_MAX, trip);
+}
+EXPORT_SYMBOL_GPL(thermal_acpi_trip_critical);

include/linux/thermal.h

@@ -346,6 +346,14 @@ int thermal_zone_get_num_trips(struct thermal_zone_device *tz);
 
 int thermal_zone_get_crit_temp(struct thermal_zone_device *tz, int *temp);
 
+#ifdef CONFIG_THERMAL_ACPI
+int thermal_acpi_trip_active(struct acpi_device *adev, int id,
+			     struct thermal_trip *trip);
+int thermal_acpi_trip_passive(struct acpi_device *adev, struct thermal_trip *trip);
+int thermal_acpi_trip_hot(struct acpi_device *adev, struct thermal_trip *trip);
+int thermal_acpi_trip_critical(struct acpi_device *adev, struct thermal_trip *trip);
+#endif
+
 #ifdef CONFIG_THERMAL
 struct thermal_zone_device *thermal_zone_device_register(const char *, int, int,
 		void *, struct thermal_zone_device_ops *,