drivers/acpi: Add a chip driver to generate thermal zone

Given the following device tree entry:
    chip drivers/acpi/thermal_zone
        register "description" = ""CPU""

        use chrome_ec as temperature_controller

        register "sensor_id" = "0"

        register "polling_period" = "10"

        register "critical_temperature" = "91"

        register "passive_config" = "{
            .temperature = 85,
        }"

        register "use_acpi1_thermal_zone_scope" = "true"

        device generic 0 on end
    end

It will generate the following:
    Scope (\_TZ)
    {
        ThermalZone (TM00)
        {
            Name (_STR, "CPU")  // _STR: Description String
            Name (_RTV, Zero)  // _RTV: Relative Temperature Values
            Name (_TZP, 0x64)  // _TZP: Thermal Zone Polling
            Name (_CRT, 0x0E39)  // _CRT: Critical Temperature
            Name (_PSV, 0x0DFD)  // _PSV: Passive Temperature
            Name (_PSL, Package (0x10)  // _PSL: Passive List
            {
                \_SB.CP00,
                \_SB.CP01,
                \_SB.CP02,
                \_SB.CP03,
                \_SB.CP04,
                \_SB.CP05,
                \_SB.CP06,
                \_SB.CP07,
                \_SB.CP08,
                \_SB.CP09,
            })
            Name (_TC1, 0x02)  // _TC1: Thermal Constant 1
            Name (_TC2, 0x05)  // _TC2: Thermal Constant 2
            Name (_TSP, 0x14)  // _TSP: Thermal Sampling Period
            Method (_TMP, 0, Serialized)  // _TMP: Temperature
            {
                Return (\_SB.PCI0.LPCB.EC0.CREC.TMP (Zero))
            }
        }
    }

BUG=b:186166365
TEST=Boot guybrush to OS and verify thermal zone works

Signed-off-by: Raul E Rangel <rrangel@chromium.org>
Change-Id: Iee2a42db749f18eef6c3f73cdbb3441567301e5d
Reviewed-on: https://review.coreboot.org/c/coreboot/+/54132
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Karthik Ramasubramanian <kramasub@google.com>

src/drivers/acpi/thermal_zone/Kconfig

@@ -0,0 +1,7 @@
+config DRIVERS_ACPI_THERMAL_ZONE
+	bool
+	default n
+	depends on HAVE_ACPI_TABLES
+	help
+	  Adds a chip driver that generates ACPI ThermalZones. See the chapter
+	  on Thermal Management in the ACPI specification.

src/drivers/acpi/thermal_zone/Makefile.inc

@@ -0,0 +1 @@
+ramstage-$(CONFIG_DRIVERS_ACPI_THERMAL_ZONE) += thermal_zone.c

src/drivers/acpi/thermal_zone/chip.h

@@ -0,0 +1,63 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+
+#ifndef __DRIVERS_ACPI_THERMAL_ZONE_H__
+#define __DRIVERS_ACPI_THERMAL_ZONE_H__
+
+#include <types.h>
+
+/*
+ * All temperature units are in Celsius.
+ * All time units are in seconds.
+ */
+struct drivers_acpi_thermal_zone_config {
+	/* Description of the thermal zone */
+	const char *description;
+
+	/*
+	 * Device that will provide the temperature reading
+	 *
+	 * This device must have an ACPI method named `TMP` that accepts the
+	 * sensor ID as the first argument. It must then return an Integer containing the
+	 * sensor's temperature in deci-Kelvin.
+	 */
+	DEVTREE_CONST struct device *temperature_controller;
+
+	/* Used to identify the temperature sensor */
+	unsigned int sensor_id;
+
+	/* The polling period in seconds for this thermal zone. */
+	unsigned int polling_period;
+
+	/* The temperature (_CRT) at which the OS must shutdown the system. */
+	unsigned int critical_temperature;
+
+	/* The temperature (_HOT) at which the OS may choose to hibernate the system */
+	unsigned int hibernate_temperature;
+
+	struct acpi_thermal_zone_passive_config {
+		/*
+		 * The temperature (_PSV) at which the OS must activate passive cooling (i.e.,
+		 * throttle the CPUs).
+		 */
+		unsigned int temperature;
+
+		/**
+		 * DeltaP[%] = _TC1 * (Tn - Tn-1) + _TC2 * (Tn - Tt)
+		 * Where:
+		 * Tn = current temperature
+		 * Tt = target temperature (_PSV)
+		 *
+		 * If any of these values are 0, then one of the following defaults will be
+		 * used: TC1: 2, TC2: 5, TSP: 10
+		 */
+		unsigned int time_constant_1;
+		unsigned int time_constant_2;
+		unsigned int time_sampling_period;
+
+	} passive_config;
+
+	/* Place the ThermalZone in the \_TZ scope */
+	bool use_acpi1_thermal_zone_scope;
+};
+
+#endif /* __DRIVERS_ACPI_THERMAL_ZONE_H__ */

src/drivers/acpi/thermal_zone/thermal_zone.c

@@ -0,0 +1,131 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+
+#include <acpi/acpigen.h>
+#include <assert.h>
+#include <commonlib/bsd/helpers.h>
+#include <console/console.h>
+#include <device/device.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include "chip.h"
+
+#define TZ_DEVICE_PATH	"\\_TZ"
+/* These defaults should be good enough for most systems */
+#define DEFAULT_TC1	2
+#define DEFAULT_TC2	5
+#define DEFAULT_TSP	10
+
+#define CELSIUS_TO_DECI_KELVIN(temp_c)	((temp_c) * 10 + 2731)
+#define SECONDS_TO_DECI_SECONDS(s)	((s) * 10)
+
+static const char *thermal_zone_acpi_name(const struct device *dev)
+{
+	char *name;
+
+	if (dev->path.type != DEVICE_PATH_GENERIC)
+		return NULL;
+
+	name = malloc(ACPI_NAME_BUFFER_SIZE);
+	snprintf(name, ACPI_NAME_BUFFER_SIZE, "TM%02X", dev->path.generic.id);
+
+	return name;
+}
+
+static void thermal_zone_fill_ssdt(const struct device *dev)
+{
+	struct drivers_acpi_thermal_zone_config *config = config_of(dev);
+	const char *scope;
+	const char *name;
+
+	assert(dev->path.type == DEVICE_PATH_GENERIC);
+
+	if (config->use_acpi1_thermal_zone_scope)
+		scope = TZ_DEVICE_PATH;
+	else
+		scope = acpi_device_scope(dev);
+
+	name = acpi_device_name(dev);
+
+	assert(name);
+	assert(scope);
+
+	if (!config->temperature_controller) {
+		printk(BIOS_ERR, "%s: missing temperature_controller\n", dev_path(dev));
+		return;
+	}
+
+	printk(BIOS_INFO, "%s.%s: %s at %s\n", scope, name, dev->chip_ops->name, dev_path(dev));
+
+	acpigen_write_scope(scope);
+	acpigen_write_thermal_zone(name);
+
+	if (config->description)
+		acpigen_write_name_string("_STR", config->description);
+
+	if (config->polling_period)
+		acpigen_write_name_integer(
+			"_TZP", SECONDS_TO_DECI_SECONDS(config->polling_period));
+
+	if (config->critical_temperature)
+		acpigen_write_name_integer(
+			"_CRT", CELSIUS_TO_DECI_KELVIN(config->critical_temperature));
+
+	if (config->hibernate_temperature)
+		acpigen_write_name_integer(
+			"_HOT", CELSIUS_TO_DECI_KELVIN(config->hibernate_temperature));
+
+	if (config->passive_config.temperature) {
+		acpigen_write_name_integer(
+			"_PSV", CELSIUS_TO_DECI_KELVIN(config->passive_config.temperature));
+
+		/*
+		 * The linux kernel currently has an artificial limit of 10 on the number of
+		 * references that can be returned in a list. If we don't respect this limit,
+		 * then the passive threshold won't work.
+		 *
+		 * See https://source.chromium.org/chromiumos/chromiumos/codesearch/+/main:src/third_party/kernel/v5.10/include/acpi/acpi_bus.h;l=19
+		 */
+		acpigen_write_processor_package("_PSL", 0, MIN(10, dev_count_cpu()));
+
+		acpigen_write_name_integer("_TC1", config->passive_config.time_constant_1
+							   ?: DEFAULT_TC1);
+		acpigen_write_name_integer("_TC2", config->passive_config.time_constant_2
+							   ?: DEFAULT_TC2);
+		acpigen_write_name_integer(
+			"_TSP",
+			SECONDS_TO_DECI_SECONDS(config->passive_config.time_sampling_period
+							?: DEFAULT_TSP));
+	}
+
+	/*
+	 * Method (_TMP) {
+	 *   Return (<path>.TMP(<sensor_id>))
+	 * }
+	 */
+	acpigen_write_method_serialized("_TMP", 0);
+	acpigen_emit_byte(RETURN_OP);
+	acpigen_emit_namestring(acpi_device_path_join(config->temperature_controller, "TMP"));
+	acpigen_write_integer(config->sensor_id);
+	acpigen_write_method_end();
+
+	acpigen_write_thermal_zone_end();
+	acpigen_write_scope_end();
+}
+
+static struct device_operations thermal_zone_ops = {
+	.read_resources		= noop_read_resources,
+	.set_resources		= noop_set_resources,
+	.acpi_name		= thermal_zone_acpi_name,
+	.acpi_fill_ssdt		= thermal_zone_fill_ssdt,
+};
+
+static void thermal_zone_enable_dev(struct device *dev)
+{
+	dev->ops = &thermal_zone_ops;
+}
+
+struct chip_operations drivers_acpi_thermal_zone_ops = {
+	CHIP_NAME("ACPI Thermal Zone")
+	.enable_dev = thermal_zone_enable_dev,
+};