cpufreq: Add Loongson-3 CPUFreq driver support

Some of LoongArch processors (Loongson-3 series) support DVFS, their
IOCSR.FEATURES has IOCSRF_FREQSCALE set. And they has a micro-core in
the package called SMC (System Management Controller), which can be
used to detect temperature, control fans, scale frequency and voltage,
etc.

The Loongson-3 CPUFreq driver is very simple now, it communicate with
SMC, get DVFS info, set target frequency from CPUFreq core, and so on.

There is a command list to interact with SMC, widely-used commands in
the CPUFreq driver include:

CMD_GET_VERSION: Get SMC firmware version.

CMD_GET_FEATURE: Get enabled SMC features.

CMD_SET_FEATURE: Enable SMC features, such as basic DVFS, BOOST.

CMD_GET_FREQ_LEVEL_NUM: Get the number of all frequency levels.

CMD_GET_FREQ_BOOST_LEVEL: Get the first boost frequency level.

CMD_GET_FREQ_LEVEL_INFO: Get the detail info of a frequency level.

CMD_GET_FREQ_INFO: Get the current frequency.

CMD_SET_FREQ_INFO: Set the target frequency.

In future we will add automatic frequency scaling, which is similar to
Intel's HWP (HardWare P-State).

Signed-off-by: Binbin Zhou <[e-mail]>
Signed-off-by: Huacai Chen <[e-mail]>
[ Viresh: Minor formatting cleanups, change return type of exit() to
void and use devm_mutex_init() ]
Signed-off-by: Viresh Kumar <[e-mail]>

MAINTAINERS

···
 F:	Documentation/translations/zh_CN/arch/loongarch/
 F:	arch/loongarch/
 F:	drivers/*/*loongarch*
+F:	drivers/cpufreq/loongson3_cpufreq.c
 
 LOONGSON GPIO DRIVER
 M:	Yinbo Zhu <[e-mail]>

drivers/cpufreq/Kconfig

···
 	  If in doubt, say N.
 endif
 
+if LOONGARCH
+config LOONGSON3_CPUFREQ
+	tristate "Loongson3 CPUFreq Driver"
+	help
+	  This option adds a CPUFreq driver for Loongson processors which
+	  support software configurable cpu frequency.
+
+	  Loongson-3 family processors support this feature.
+
+	  If in doubt, say N.
+endif
+
 if SPARC64
 config SPARC_US3_CPUFREQ
 	tristate "UltraSPARC-III CPU Frequency driver"

drivers/cpufreq/Makefile

···
 # Other platform drivers
 obj-$(CONFIG_BMIPS_CPUFREQ)		+= bmips-cpufreq.o
 obj-$(CONFIG_LOONGSON2_CPUFREQ)		+= loongson2_cpufreq.o
+obj-$(CONFIG_LOONGSON3_CPUFREQ)		+= loongson3_cpufreq.o
 obj-$(CONFIG_SH_CPU_FREQ)		+= sh-cpufreq.o
 obj-$(CONFIG_SPARC_US2E_CPUFREQ)	+= sparc-us2e-cpufreq.o
 obj-$(CONFIG_SPARC_US3_CPUFREQ)		+= sparc-us3-cpufreq.o

drivers/cpufreq/loongson3_cpufreq.c

···
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * CPUFreq driver for the Loongson-3 processors.
+ *
+ * All revisions of Loongson-3 processor support cpu_has_scalefreq feature.
+ *
+ * Author: Huacai Chen <[e-mail]>
+ * Copyright (C) 2024 Loongson Technology Corporation Limited
+ */
+#include <linux/cpufreq.h>
+#include <linux/delay.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/units.h>
+
+#include <asm/idle.h>
+#include <asm/loongarch.h>
+#include <asm/loongson.h>
+
+/* Message */
+union smc_message {
+	u32 value;
+	struct {
+		u32 id		: 4;
+		u32 info	: 4;
+		u32 val		: 16;
+		u32 cmd		: 6;
+		u32 extra	: 1;
+		u32 complete	: 1;
+	};
+};
+
+/* Command return values */
+#define CMD_OK				0 /* No error */
+#define CMD_ERROR			1 /* Regular error */
+#define CMD_NOCMD			2 /* Command does not support */
+#define CMD_INVAL			3 /* Invalid Parameter */
+
+/* Version commands */
+/*
+ * CMD_GET_VERSION - Get interface version
+ * Input: none
+ * Output: version
+ */
+#define CMD_GET_VERSION			0x1
+
+/* Feature commands */
+/*
+ * CMD_GET_FEATURE - Get feature state
+ * Input: feature ID
+ * Output: feature flag
+ */
+#define CMD_GET_FEATURE			0x2
+
+/*
+ * CMD_SET_FEATURE - Set feature state
+ * Input: feature ID, feature flag
+ * output: none
+ */
+#define CMD_SET_FEATURE			0x3
+
+/* Feature IDs */
+#define FEATURE_SENSOR			0
+#define FEATURE_FAN			1
+#define FEATURE_DVFS			2
+
+/* Sensor feature flags */
+#define FEATURE_SENSOR_ENABLE		BIT(0)
+#define FEATURE_SENSOR_SAMPLE		BIT(1)
+
+/* Fan feature flags */
+#define FEATURE_FAN_ENABLE		BIT(0)
+#define FEATURE_FAN_AUTO		BIT(1)
+
+/* DVFS feature flags */
+#define FEATURE_DVFS_ENABLE		BIT(0)
+#define FEATURE_DVFS_BOOST		BIT(1)
+#define FEATURE_DVFS_AUTO		BIT(2)
+#define FEATURE_DVFS_SINGLE_BOOST	BIT(3)
+
+/* Sensor commands */
+/*
+ * CMD_GET_SENSOR_NUM - Get number of sensors
+ * Input: none
+ * Output: number
+ */
+#define CMD_GET_SENSOR_NUM		0x4
+
+/*
+ * CMD_GET_SENSOR_STATUS - Get sensor status
+ * Input: sensor ID, type
+ * Output: sensor status
+ */
+#define CMD_GET_SENSOR_STATUS		0x5
+
+/* Sensor types */
+#define SENSOR_INFO_TYPE		0
+#define SENSOR_INFO_TYPE_TEMP		1
+
+/* Fan commands */
+/*
+ * CMD_GET_FAN_NUM - Get number of fans
+ * Input: none
+ * Output: number
+ */
+#define CMD_GET_FAN_NUM			0x6
+
+/*
+ * CMD_GET_FAN_INFO - Get fan status
+ * Input: fan ID, type
+ * Output: fan info
+ */
+#define CMD_GET_FAN_INFO		0x7
+
+/*
+ * CMD_SET_FAN_INFO - Set fan status
+ * Input: fan ID, type, value
+ * Output: none
+ */
+#define CMD_SET_FAN_INFO		0x8
+
+/* Fan types */
+#define FAN_INFO_TYPE_LEVEL		0
+
+/* DVFS commands */
+/*
+ * CMD_GET_FREQ_LEVEL_NUM - Get number of freq levels
+ * Input: CPU ID
+ * Output: number
+ */
+#define CMD_GET_FREQ_LEVEL_NUM		0x9
+
+/*
+ * CMD_GET_FREQ_BOOST_LEVEL - Get the first boost level
+ * Input: CPU ID
+ * Output: number
+ */
+#define CMD_GET_FREQ_BOOST_LEVEL	0x10
+
+/*
+ * CMD_GET_FREQ_LEVEL_INFO - Get freq level info
+ * Input: CPU ID, level ID
+ * Output: level info
+ */
+#define CMD_GET_FREQ_LEVEL_INFO		0x11
+
+/*
+ * CMD_GET_FREQ_INFO - Get freq info
+ * Input: CPU ID, type
+ * Output: freq info
+ */
+#define CMD_GET_FREQ_INFO		0x12
+
+/*
+ * CMD_SET_FREQ_INFO - Set freq info
+ * Input: CPU ID, type, value
+ * Output: none
+ */
+#define CMD_SET_FREQ_INFO		0x13
+
+/* Freq types */
+#define FREQ_INFO_TYPE_FREQ		0
+#define FREQ_INFO_TYPE_LEVEL		1
+
+#define FREQ_MAX_LEVEL			16
+
+struct loongson3_freq_data {
+	unsigned int def_freq_level;
+	struct cpufreq_frequency_table table[];
+};
+
+static struct mutex cpufreq_mutex[MAX_PACKAGES];
+static struct cpufreq_driver loongson3_cpufreq_driver;
+static DEFINE_PER_CPU(struct loongson3_freq_data *, freq_data);
+
+static inline int do_service_request(u32 id, u32 info, u32 cmd, u32 val, u32 extra)
+{
+	int retries;
+	unsigned int cpu = smp_processor_id();
+	unsigned int package = cpu_data[cpu].package;
+	union smc_message msg, last;
+
+	mutex_lock(&cpufreq_mutex[package]);
+
+	last.value = iocsr_read32(LOONGARCH_IOCSR_SMCMBX);
+	if (!last.complete) {
+		mutex_unlock(&cpufreq_mutex[package]);
+		return -EPERM;
+	}
+
+	msg.id		= id;
+	msg.info	= info;
+	msg.cmd		= cmd;
+	msg.val		= val;
+	msg.extra	= extra;
+	msg.complete	= 0;
+
+	iocsr_write32(msg.value, LOONGARCH_IOCSR_SMCMBX);
+	iocsr_write32(iocsr_read32(LOONGARCH_IOCSR_MISC_FUNC) | IOCSR_MISC_FUNC_SOFT_INT,
+		      LOONGARCH_IOCSR_MISC_FUNC);
+
+	for (retries = 0; retries < 10000; retries++) {
+		msg.value = iocsr_read32(LOONGARCH_IOCSR_SMCMBX);
+		if (msg.complete)
+			break;
+
+		usleep_range(8, 12);
+	}
+
+	if (!msg.complete || msg.cmd != CMD_OK) {
+		mutex_unlock(&cpufreq_mutex[package]);
+		return -EPERM;
+	}
+
+	mutex_unlock(&cpufreq_mutex[package]);
+
+	return msg.val;
+}
+
+static unsigned int loongson3_cpufreq_get(unsigned int cpu)
+{
+	int ret;
+
+	ret = do_service_request(cpu, FREQ_INFO_TYPE_FREQ, CMD_GET_FREQ_INFO, 0, 0);
+
+	return ret * KILO;
+}
+
+static int loongson3_cpufreq_target(struct cpufreq_policy *policy, unsigned int index)
+{
+	int ret;
+
+	ret = do_service_request(cpu_data[policy->cpu].core,
+				 FREQ_INFO_TYPE_LEVEL, CMD_SET_FREQ_INFO, index, 0);
+
+	return (ret >= 0) ? 0 : ret;
+}
+
+static int configure_freq_table(int cpu)
+{
+	int i, ret, boost_level, max_level, freq_level;
+	struct platform_device *pdev = cpufreq_get_driver_data();
+	struct loongson3_freq_data *data;
+
+	if (per_cpu(freq_data, cpu))
+		return 0;
+
+	ret = do_service_request(cpu, 0, CMD_GET_FREQ_LEVEL_NUM, 0, 0);
+	if (ret < 0)
+		return ret;
+	max_level = ret;
+
+	ret = do_service_request(cpu, 0, CMD_GET_FREQ_BOOST_LEVEL, 0, 0);
+	if (ret < 0)
+		return ret;
+	boost_level = ret;
+
+	freq_level = min(max_level, FREQ_MAX_LEVEL);
+	data = devm_kzalloc(&pdev->dev, struct_size(data, table, freq_level + 1), GFP_KERNEL);
+	if (!data)
+		return -ENOMEM;
+
+	data->def_freq_level = boost_level - 1;
+
+	for (i = 0; i < freq_level; i++) {
+		ret = do_service_request(cpu, FREQ_INFO_TYPE_FREQ, CMD_GET_FREQ_LEVEL_INFO, i, 0);
+		if (ret < 0) {
+			devm_kfree(&pdev->dev, data);
+			return ret;
+		}
+
+		data->table[i].frequency = ret * KILO;
+		data->table[i].flags = (i >= boost_level) ? CPUFREQ_BOOST_FREQ : 0;
+	}
+
+	data->table[freq_level].flags = 0;
+	data->table[freq_level].frequency = CPUFREQ_TABLE_END;
+
+	per_cpu(freq_data, cpu) = data;
+
+	return 0;
+}
+
+static int loongson3_cpufreq_cpu_init(struct cpufreq_policy *policy)
+{
+	int i, ret, cpu = policy->cpu;
+
+	ret = configure_freq_table(cpu);
+	if (ret < 0)
+		return ret;
+
+	policy->cpuinfo.transition_latency = 10000;
+	policy->freq_table = per_cpu(freq_data, cpu)->table;
+	policy->suspend_freq = policy->freq_table[per_cpu(freq_data, cpu)->def_freq_level].frequency;
+	cpumask_copy(policy->cpus, topology_sibling_cpumask(cpu));
+
+	for_each_cpu(i, policy->cpus) {
+		if (i != cpu)
+			per_cpu(freq_data, i) = per_cpu(freq_data, cpu);
+	}
+
+	if (policy_has_boost_freq(policy)) {
+		ret = cpufreq_enable_boost_support();
+		if (ret < 0) {
+			pr_warn("cpufreq: Failed to enable boost: %d\n", ret);
+			return ret;
+		}
+		loongson3_cpufreq_driver.boost_enabled = true;
+	}
+
+	return 0;
+}
+
+static void loongson3_cpufreq_cpu_exit(struct cpufreq_policy *policy)
+{
+	int cpu = policy->cpu;
+
+	loongson3_cpufreq_target(policy, per_cpu(freq_data, cpu)->def_freq_level);
+}
+
+static int loongson3_cpufreq_cpu_online(struct cpufreq_policy *policy)
+{
+	return 0;
+}
+
+static int loongson3_cpufreq_cpu_offline(struct cpufreq_policy *policy)
+{
+	return 0;
+}
+
+static struct cpufreq_driver loongson3_cpufreq_driver = {
+	.name = "loongson3",
+	.flags = CPUFREQ_CONST_LOOPS,
+	.init = loongson3_cpufreq_cpu_init,
+	.exit = loongson3_cpufreq_cpu_exit,
+	.online = loongson3_cpufreq_cpu_online,
+	.offline = loongson3_cpufreq_cpu_offline,
+	.get = loongson3_cpufreq_get,
+	.target_index = loongson3_cpufreq_target,
+	.attr = cpufreq_generic_attr,
+	.verify = cpufreq_generic_frequency_table_verify,
+	.suspend = cpufreq_generic_suspend,
+};
+
+static int loongson3_cpufreq_probe(struct platform_device *pdev)
+{
+	int i, ret;
+
+	for (i = 0; i < MAX_PACKAGES; i++)
+		devm_mutex_init(&pdev->dev, &cpufreq_mutex[i]);
+
+	ret = do_service_request(0, 0, CMD_GET_VERSION, 0, 0);
+	if (ret <= 0)
+		return -EPERM;
+
+	ret = do_service_request(FEATURE_DVFS, 0, CMD_SET_FEATURE,
+				 FEATURE_DVFS_ENABLE | FEATURE_DVFS_BOOST, 0);
+	if (ret < 0)
+		return -EPERM;
+
+	loongson3_cpufreq_driver.driver_data = pdev;
+
+	ret = cpufreq_register_driver(&loongson3_cpufreq_driver);
+	if (ret)
+		return ret;
+
+	pr_info("cpufreq: Loongson-3 CPU frequency driver.\n");
+
+	return 0;
+}
+
+static void loongson3_cpufreq_remove(struct platform_device *pdev)
+{
+	cpufreq_unregister_driver(&loongson3_cpufreq_driver);
+}
+
+static struct platform_device_id cpufreq_id_table[] = {
+	{ "loongson3_cpufreq", },
+	{ /* sentinel */ }
+};
+MODULE_DEVICE_TABLE(platform, cpufreq_id_table);
+
+static struct platform_driver loongson3_platform_driver = {
+	.driver = {
+		.name = "loongson3_cpufreq",
+	},
+	.id_table = cpufreq_id_table,
+	.probe = loongson3_cpufreq_probe,
+	.remove_new = loongson3_cpufreq_remove,
+};
+module_platform_driver(loongson3_platform_driver);
+
+MODULE_AUTHOR("Huacai Chen <[e-mail]>");
+MODULE_DESCRIPTION("CPUFreq driver for Loongson-3 processors");
+MODULE_LICENSE("GPL");