Linux thermal框架介绍

RK3568温控

cat /sys/class/thermal/thermal_zone0/temp
cat /sys/class/thermal/thermal_zone1/temp
cat /sys/class/thermal/cooling_device0/cur_state
cat /sys/class/thermal/cooling_device1/cur_state
cat /sys/class/thermal/cooling_device2/cur_state

thermal_zone0：是soc的温度；

thermal_zone1: 是gpu的温度。

冷却设备有三个：

功能介绍

Linux的Thermal机制是基于Zone为单位的热管理机制，核心包括三个部分：获取区域温度的设备thermal_zone_device、区域降温的设备thermal_cooling_device、温控策略thermal_governor。thermal_governor从thermal_zone_device获取区域温度，然后根据当前温度，决定调用哪个降温设备来为该区域降温。

（1）Thermal sensor driver：SoC内部CPU和GPU的旁边通常会有用于获取它们温度的传感器，比如 tsadc（Temperature Sensor ADC）。

注：

ADC，即Analog-to-Digital Converter（模拟数字转换器）

ADC的作用：将连续变化的模拟信号转换离散的数字信号的器件
常见的模拟信号：温度、压力、声音
AD转换步骤：采样、量化、编码

（2）Thermal cooling device：降温设备，比如风扇。这里有点特殊的是，CPU和GPU不仅是发热设备（即需要实施温控策略的设备），也可以是降温设备。当我们降低CPU/GPU的运行频率的时候，它们就在充当降温设备（降低产热量即是在降温）。

（3）Thermal governer：温控策略，Linux内核中的温控策略要比上面的空调控制精细得多，而且也提供了多种策略。

（4）Thermal core：组织并管理上面三个组件，并通过sysfs和用户空间交互。

归纳一下：核心为thermal_core；可以获取温度的设备抽象为thermal_zone_device，如Temp Sensor、NTC（板上的热敏电阻）等；控制温度的设备抽象为thermal_cooling_device，如风扇、CPU、DDR、GPU等；温控策略抽象为thermal_governor，如step_wise、bang_bang等。

linux thermal框架

Linux Thermal框架可以分为Thermal Core、Thermal Governor、Thermal Cooling、Thermal Driver以及Thermal Device Tree五大部分。

Thermal Core：用于和user space、Thermal Governor、Thermal Driver交互。

Thermal Governor：主要包括gov_bang_bang、gov_fair_share、gov_power_allocator、gov_step_wise、gov_user_space等，最常用的为gov_power_allocator.

Thermal Cooling：主要包括cpufreq_cooling、cpuidle_cooling、devfreq_cooling等。

thermal core

内核将采集区域温度的设备抽象为结构体struct thermal_zone_device，主要成员包括char type[]设备名称；int temperature当前温度；int last_temperature上次采集问题；struct thermal_governer *governor对应governor； int polling_delay温度采集时间间隔等等。其中struct thermal_zone_device_ops *ops是采集区域温度设备的操作抽象，包括绑定降温设备，获取设备温度等。

kernel/linux/thermal.h中定义了thernal_zone_device & thermal_zone_device_ops、thermal_governor、thermal_cooling_device & thermal_cooling_device_ops结构体。

struct thermal_zone_device {
        int id;    // 设备的唯一标识符
        char type[THERMAL_NAME_LENGTH];    // 设备名称
        struct device device;    // 设备相关联的struct device结构体
        struct thermal_attr *trip_temp_attrs;    // 温度触发器（trip）的温度属性链表
        struct thermal_attr *trip_type_attrs;    // 温度触发器的触发类型属性链表
        struct thermal_attr *trip_hyst_attrs;    // 温度触发器的滞后属性链表
        void *devdata;
        int trips;
        unsigned long trips_disabled;        /* bitmap for disabled trips */
        int passive_delay;
        int polling_delay;    // 采集温度的时间间隔
        int temperature;    // 当前采集的温度
        int last_temperature;    // 上次采集的温度
        int emul_temperature;
        int passive;
        unsigned int forced_passive;    // 强制进入被动散热模式的标志
        atomic_t need_update;
        struct thermal_zone_device_ops *ops;    // 区域温度设备的操作
        struct thermal_zone_params *tzp;    // 记录一些信息，如governor name
        struct thermal_governor *governor;    // 温控策略
        void *governor_data;    
        struct list_head thermal_instances;    // 降温设备
        struct idr idr;    // 管理热区设备实例的ID
        struct mutex lock;
        struct list_head node;    // 热区设备的链表节点
        struct delayed_work poll_queue;    // 用于轮询区域温度
};
 
struct thermal_zone_params {
        char governor_name[THERMAL_NAME_LENGTH];
 
        /*
         * a boolean to indicate if the thermal to hwmon sysfs interface
         * is required. when no_hwmon == false, a hwmon sysfs interface
         * will be created. when no_hwmon == true, nothing will be done
         */
        bool no_hwmon;
 
        int num_tbps;        /* Number of tbp entries */
        struct thermal_bind_params *tbp;
 
        /*
         * Sustainable power (heat) that this thermal zone can dissipate in
         * mW
         */
        u32 sustainable_power;
 
        /*
         * Proportional parameter of the PID controller when
         * overshooting (i.e., when temperature is below the target)
         */
        s32 k_po;
 
        /*
         * Proportional parameter of the PID controller when
         * undershooting
         */
        s32 k_pu;
 
        /* Integral parameter of the PID controller */
        s32 k_i;
 
        /* Derivative parameter of the PID controller */
        s32 k_d;
 
        /* threshold below which the error is no longer accumulated */
        s32 integral_cutoff;
 
        /*
         * @slope:        slope of a linear temperature adjustment curve.
         *                 Used by thermal zone drivers.
         */
        int slope;
        /*
         * @offset:        offset of a linear temperature adjustment curve.
         *                 Used by thermal zone drivers (default 0).
         */
        int offset;
};
 
struct thermal_zone_device_ops {
        // 绑定一个降温设备到该热区设备
        int (*bind) (struct thermal_zone_device *,
                     struct thermal_cooling_device *);
        // 解绑一个降温设备从该热区设备
        int (*unbind) (struct thermal_zone_device *,
                       struct thermal_cooling_device *);
        // 获取当前热区设备的温度
        int (*get_temp) (struct thermal_zone_device *, int *);
        // 获取当前热区设备的工作模式
        int (*get_mode) (struct thermal_zone_device *,
                         enum thermal_device_mode *);
        // 设置当前热区设备的工作模式              
        int (*set_mode) (struct thermal_zone_device *,
                enum thermal_device_mode);
        // 获取指定温度触发器的触发类型        
        int (*get_trip_type) (struct thermal_zone_device *, int,
                enum thermal_trip_type *);
        // 获取触发等级对应的温度     
        int (*get_trip_temp) (struct thermal_zone_device *, int, int *);
        // 设置触发等级对应的温度
        int (*set_trip_temp) (struct thermal_zone_device *, int, int);
        int (*get_trip_hyst) (struct thermal_zone_device *, int, int *);
        int (*set_trip_hyst) (struct thermal_zone_device *, int, int);
        int (*get_crit_temp) (struct thermal_zone_device *, int *);
        int (*set_emul_temp) (struct thermal_zone_device *, int);
        // 获取温度的变化趋势
        int (*get_trend) (struct thermal_zone_device *, int,
                          enum thermal_trend *);
        int (*notify) (struct thermal_zone_device *, int,
                       enum thermal_trip_type);
};
 
// 内核将温控策略抽象为结构体struct thermal_governor，
//主要成员包括：char name[THERMAL_NAME_LENGTH]策略名称；int (*throttle)()温控决策等等。
struct thermal_governor {
        char name[THERMAL_NAME_LENGTH];
        int (*bind_to_tz)(struct thermal_zone_device *tz);
        void (*unbind_from_tz)(struct thermal_zone_device *tz);
        int (*throttle)(struct thermal_zone_device *tz, int trip);
        struct list_head        governor_list;
};
// 执行温控策略的设备成为区域降温设备，
//内核抽象为结构体struct thermal_cooling_device，struct thermal_cooling_device_ops是区域降温设备的操作集合。
struct thermal_cooling_device {
        int id;                           //每个thermal_cooling_device有独立的id
        char type[THERMAL_NAME_LENGTH];   // 名称
        struct device device;
        struct device_node *np;
        void *devdata;
        const struct thermal_cooling_device_ops *ops;
        bool updated; /* true if the cooling device does not need update */
        struct mutex lock; /* protect thermal_instances list */
        struct list_head thermal_instances;
        struct list_head node;
};
 
struct thermal_cooling_device_ops {
        //获取总的状态数，相当于降温等级
        int (*get_max_state) (struct thermal_cooling_device *, unsigned long *); 
        //获取当前状态  
        int (*get_cur_state) (struct thermal_cooling_device *, unsigned long *);  
        //设置状态  
        int (*set_cur_state) (struct thermal_cooling_device *, unsigned long); 
        // 获取所请求的功率     
        int (*get_requested_power)(struct thermal_cooling_device *,
                                   struct thermal_zone_device *, u32 *);
        // 将指定状态（降温等级）转换为对应的功率                          
        int (*state2power)(struct thermal_cooling_device *,
                           struct thermal_zone_device *, unsigned long, u32 *);
        // 将指定功率转换为对应的状态（降温等级）                   
        int (*power2state)(struct thermal_cooling_device *,
                           struct thermal_zone_device *, u32, unsigned long *);
};

初始化

thermal_governor注册

以step_wise governor为例：

int thermal_gov_step_wise_register(void)
{
        // 调用thermal_core.c中的方法
        return thermal_register_governor(&thermal_gov_step_wise);
}

static int __init thermal_init(void)
{
        int result;
        // 注册所有的governors       
        result = thermal_register_governors();
        if (result)
                goto error;
 
        result = class_register(&thermal_class);
        if (result)
                goto unregister_governors;
 
        result = genetlink_init();
        if (result)
                goto unregister_class;
 
        result = of_parse_thermal_zones();
        if (result)
                goto exit_netlink;
 
        result = register_pm_notifier(&thermal_pm_nb);
        if (result)
                pr_warn("Thermal: Can not register suspend notifier, return %d\n",
                        result);
 
        return 0;
 
exit_netlink:
        genetlink_exit();
unregister_class:
        class_unregister(&thermal_class);
unregister_governors:
        thermal_unregister_governors();
error:
        idr_destroy(&thermal_tz_idr);
        idr_destroy(&thermal_cdev_idr);
        mutex_destroy(&thermal_idr_lock);
        mutex_destroy(&thermal_list_lock);
        mutex_destroy(&thermal_governor_lock);
        return result;
}
 
static int __init thermal_register_governors(void)
{
        int result;
        // 调用step_wise governor中的方法，为系统默认的gov
        result = thermal_gov_step_wise_register();
        if (result)
                return result;
 
        result = thermal_gov_fair_share_register();
        if (result)
                return result;
 
        result = thermal_gov_bang_bang_register();
        if (result)
                return result;
 
        result = thermal_gov_user_space_register();
        if (result)
                return result;
        // 注册IPA governor
        return thermal_gov_power_allocator_register();
}
 
// 将第一个注册的governor设置为系统默认governor，即step_wise governor
int thermal_register_governor(struct thermal_governor *governor)
{
        int err;
        const char *name;
        struct thermal_zone_device *pos;
 
        if (!governor)
                return -EINVAL;
 
        mutex_lock(&thermal_governor_lock);
 
        err = -EBUSY;
        if (__find_governor(governor->name) == NULL) {
                err = 0;
                //链接到thermal_governor_list
                list_add(&governor->governor_list, &thermal_governor_list);
                if (!def_governor && !strncmp(governor->name,
                        DEFAULT_THERMAL_GOVERNOR, THERMAL_NAME_LENGTH))
                        def_governor = governor; //第一个设置为def_governor
        }
    .......
}

thermal_zone_device注册

struct thermal_zone_device *thermal_zone_device_register(const char *type,
        int trips, int mask, void *devdata,
        struct thermal_zone_device_ops *ops,
        struct thermal_zone_params *tzp,
        int passive_delay, int polling_delay)
{
        struct thermal_zone_device *tz;
        enum thermal_trip_type trip_type;
        int trip_temp;
        int result;
        int count;
        int passive = 0;
        struct thermal_governor *governor;
        .........................................................................
    //分配内存
        tz = kzalloc(sizeof(struct thermal_zone_device), GFP_KERNEL);
    .........................................................................
        //初始化idr，并获取id
        idr_init(&tz->idr);
        mutex_init(&tz->lock);
        result = get_idr(&thermal_tz_idr, &thermal_idr_lock, &tz->id);
        ..........................................................................
        strlcpy(tz->type, type ? : "", sizeof(tz->type));  //设置名称
        tz->ops = ops;    //操作集合
        tz->tzp = tzp;    //参数
        tz->device.class = &thermal_class;
        tz->devdata = devdata;
        tz->trips = trips;
        tz->passive_delay = passive_delay;
        tz->polling_delay = polling_delay;   //采集时间间隔
        /* A new thermal zone needs to be updated anyway. */
        atomic_set(&tz->need_update, 1);
    ........................................................................
        //根据governor name，设置降温策略
        if (tz->tzp)
                governor = __find_governor(tz->tzp->governor_name);
        else
                governor = def_governor;
    .........
        //链接到thermal_tz_list
        mutex_lock(&thermal_list_lock);
        list_add_tail(&tz->node, &thermal_tz_list);
        mutex_unlock(&thermal_list_lock);
 
        /* 尝试绑定已注册的降温设备 */
        bind_tz(tz);
 
        thermal_zone_device_reset(tz);
        /* Update the new thermal zone and mark it as already updated. */
        if (atomic_cmpxchg(&tz->need_update, 1, 0))
                thermal_zone_device_update(tz, THERMAL_EVENT_UNSPECIFIED);
 
        return tz;
    ..........
}

thermal_cooling_device注册

struct thermal_cooling_device *
thermal_cooling_device_register(char *type, void *devdata,
                                const struct thermal_cooling_device_ops *ops)
{
        return __thermal_cooling_device_register(NULL, type, devdata, ops);
}
 
static struct thermal_cooling_device *
__thermal_cooling_device_register(struct device_node *np,
                                  char *type, void *devdata,
                                  const struct thermal_cooling_device_ops *ops)
{
        struct thermal_cooling_device *cdev;
        struct thermal_zone_device *pos = NULL;
        int result;
 
        if (type && strlen(type) >= THERMAL_NAME_LENGTH)
                return ERR_PTR(-EINVAL);
 
        if (!ops || !ops->get_max_state || !ops->get_cur_state ||
            !ops->set_cur_state)
                return ERR_PTR(-EINVAL);
        // 分配内存
        cdev = kzalloc(sizeof(struct thermal_cooling_device), GFP_KERNEL);
        if (!cdev)
                return ERR_PTR(-ENOMEM);
 
        result = get_idr(&thermal_cdev_idr, &thermal_idr_lock, &cdev->id);
        if (result) {
                kfree(cdev);
                return ERR_PTR(result);
        }
 
        strlcpy(cdev->type, type ? : "", sizeof(cdev->type));
        mutex_init(&cdev->lock);
        INIT_LIST_HEAD(&cdev->thermal_instances);
        // 初始化成员，将mtk的ops和devdata赋值给thermal_cooling_device 
        cdev->np = np;
        cdev->ops = ops;
        cdev->updated = false;
        cdev->device.class = &thermal_class;
        cdev->device.groups = cooling_device_attr_groups;
        cdev->devdata = devdata;
        dev_set_name(&cdev->device, "cooling_device%d", cdev->id);
        // 注册device
        result = device_register(&cdev->device);
        if (result) {
                release_idr(&thermal_cdev_idr, &thermal_idr_lock, cdev->id);
                kfree(cdev);
                return ERR_PTR(result);
        }
 
        /* Add 'this' new cdev to the global cdev list */
        // 新的thermal_cooling_device加入到thermal_cdev_list链表
        mutex_lock(&thermal_list_lock);
        list_add(&cdev->node, &thermal_cdev_list);
        mutex_unlock(&thermal_list_lock);
 
        /* Update binding information for 'this' new cdev */
        // 尝试绑定到已注册的温度采集设备thermal_zone_device 
        bind_cdev(cdev);
 
        mutex_lock(&thermal_list_lock);
        list_for_each_entry(pos, &thermal_tz_list, node)
                if (atomic_cmpxchg(&pos->need_update, 1, 0))
                        thermal_zone_device_update(pos);
        mutex_unlock(&thermal_list_lock);
 
        return cdev;
}
 
static void bind_cdev(struct thermal_cooling_device *cdev)
{
        int i, ret;
        const struct thermal_zone_params *tzp;
        struct thermal_zone_device *pos = NULL;
 
        mutex_lock(&thermal_list_lock);
        // 遍历thermal_zone_device list，逐个绑定thermal_cooling_device 
        list_for_each_entry(pos, &thermal_tz_list, node) {
                if (!pos->tzp && !pos->ops->bind)
                        continue;
 
                if (pos->ops->bind) {
                        // 调用 thermal_zone_device中thermal_zone_device_ops成员中的bind方法
                        ret = pos->ops->bind(pos, cdev);
                        if (ret)
                                print_bind_err_msg(pos, cdev, ret);
                        continue;
                }
 
                tzp = pos->tzp;
                if (!tzp || !tzp->tbp)
                        continue;
 
                for (i = 0; i < tzp->num_tbps; i++) {
                        if (tzp->tbp[i].cdev || !tzp->tbp[i].match)
                                continue;
                        if (tzp->tbp[i].match(pos, cdev))
                                continue;
                        tzp->tbp[i].cdev = cdev;
                        __bind(pos, tzp->tbp[i].trip_mask, cdev,
                               tzp->tbp[i].binding_limits,
                               tzp->tbp[i].weight);
                }
        }
 
        mutex_unlock(&thermal_list_lock);
}

温度采集设备与降温设备的联系

同一个温度采集设备可以对应多个降温设备，结构体struct thermal_instance用于连接温度采集设备与降温设备，成员struct thermal_zone_device *tz是对应的温度采集设备，struct thermal_cooling_device *cdev是对应的降温设备，int trip触发登记（对应一个温度），当温度采集设备采集的温度达到一定值时，调用对应trip登记的降温设备。

struct thermal_instance {
    .................................................................
        struct thermal_zone_device *tz;      //对应温度采集设备
        struct thermal_cooling_device *cdev; //对应降温设备
        int trip;                            //触发等级
        struct list_head tz_node;            //链接到温度采集设备
        struct list_head cdev_node;          //链接到降温设备
    .................................................................
};

以温度采集设备绑定降温设备为例，当温度采集设备注册时会尝试绑定所有已经注册的降温设备。以CPU为例，bind接口对应的是tscpu_bind()，从代码中可以看出如果降温设备的名称为g_bind0--g_bind9中的一个将会绑定CPU温度采集设备和降温设备。tscpu_bind()接口中也定义了各种名称降温设备对应的触发等级。

static void bind_tz(struct thermal_zone_device *tz)
{
        int i, ret;
        struct thermal_cooling_device *pos = NULL;
        const struct thermal_zone_params *tzp = tz->tzp;
 
        if (!tzp && !tz->ops->bind)
                return;
 
        mutex_lock(&thermal_list_lock);
        if (tz->ops->bind) {
            //尝试绑定所有的已经注册的降温设备
                list_for_each_entry(pos, &thermal_cdev_list, node) {
                        ret = tz->ops->bind(tz, pos);
                        if (ret)
                                print_bind_err_msg(tz, pos, ret);
                }
                goto exit;
        }
    ...........................................................
}
 
static int tscpu_bind(struct thermal_zone_device *thermal, struct thermal_cooling_device *cdev)
{
        int table_val = 0;
 
        if (!strcmp(cdev->type, g_bind0)) {
                table_val = 0;
                tscpu_config_all_tc_hw_protect(trip_temp[0], tc_mid_trip);
        } else if (!strcmp(cdev->type, g_bind1)) {
                table_val = 1;
                tc_mid_trip = trip_temp[1];
                tscpu_config_all_tc_hw_protect(trip_temp[0], tc_mid_trip);
        } else if (!strcmp(cdev->type, g_bind2)) {
                table_val = 2;
        } else if (!strcmp(cdev->type, g_bind3)) {
                table_val = 3;
        } else if (!strcmp(cdev->type, g_bind4)) {
    .....................................................
        } else {
                return 0;
        }
    //以table_val为触发等级绑定发热设备和降温设备
        if (mtk_thermal_zone_bind_cooling_device(thermal, table_val, cdev)) {
                tscpu_warn("tscpu_bind error binding cooling dev\n");
                return -EINVAL;
        }
 
        tscpu_printk("tscpu_bind binding OK, %d\n", table_val);
        return 0;
}

温度采集设备知道了触发等级和降温温度，还需要知道触发等级对应的温度。thermal_zone_device_ops的get_trip_temp()用于查询触发等级对应的温度，以mtkcpu为例，所有降温设备的触发温度保存在数据中，触发等级就是该数组的下标。

static int tscpu_get_trip_temp
(struct thermal_zone_device *thermal, int trip, int *temp)
{
        *temp = trip_temp[trip];
        return 0;
}

cooling device

以cpu coolig为例：

cpufreq_state2power：根据cpu cooling state换算cpu power。

static int cpufreq_state2power(struct thermal_cooling_device *cdev,
                               struct thermal_zone_device *tz,
                               unsigned long state, u32 *power)
{
        unsigned int freq, num_cpus;
        cpumask_t cpumask;
        u32 static_power, dynamic_power;
        int ret;
        struct cpufreq_cooling_device *cpufreq_device = cdev->devdata;
 
        cpumask_and(&cpumask, &cpufreq_device->allowed_cpus, cpu_online_mask);
        // 根据cpumask得到在线cpu核数
        num_cpus = cpumask_weight(&cpumask);
 
        /* None of our cpus are online, so no power */
        if (num_cpus == 0) {
                *power = 0;
                return 0;
        }
        // 根据cpu state得到当前的频率
        freq = cpufreq_device->freq_table[state];
        if (!freq)
                return -EINVAL;
        // 计算当前频率下的cpu动态功耗
        dynamic_power = cpu_freq_to_power(cpufreq_device, freq) * num_cpus;
        // 计算当前频率下的cpu静态功耗
        ret = get_static_power(cpufreq_device, tz, freq, &static_power);
        if (ret)
                return ret;
        // 计算当前频率下的cpu总的功耗
        *power = static_power + dynamic_power;
        return 0;
}

cpufreq_power2state：根据cpu power换算cpu cooling state.

static int cpufreq_power2state(struct thermal_cooling_device *cdev,
                               struct thermal_zone_device *tz, u32 power,
                               unsigned long *state)
{
        unsigned int cpu, cur_freq, target_freq;
        int ret;
        s32 dyn_power;
        u32 last_load, normalised_power, static_power;
        struct cpufreq_cooling_device *cpufreq_device = cdev->devdata;
 
        cpu = cpumask_any_and(&cpufreq_device->allowed_cpus, cpu_online_mask);
 
        /* None of our cpus are online */
        if (cpu >= nr_cpu_ids)
                return -ENODEV;
        // 计算当前cpu频率
        cur_freq = cpufreq_quick_get(cpu);
        // 计算当前频率下的静态功耗
        ret = get_static_power(cpufreq_device, tz, cur_freq, &static_power);
        if (ret)
                return ret;
        // 计算当前频率下的动态功耗
        dyn_power = power - static_power;
        dyn_power = dyn_power > 0 ? dyn_power : 0;
        last_load = cpufreq_device->last_load ?: 1;
        // 计算归一化功耗
        normalised_power = (dyn_power * 100) / last_load;
        // 根据归一化功耗计算出目标频率
        target_freq = cpu_power_to_freq(cpufreq_device, normalised_power);
        // 根据目标频率得到cpu state
        *state = cpufreq_cooling_get_level(cpu, target_freq);
        if (*state == THERMAL_CSTATE_INVALID) {
                dev_warn_ratelimited(&cdev->device,
                                     "Failed to convert %dKHz for cpu %d into a cdev state\n",
                                     target_freq, cpu);
                return -EINVAL;
        }
 
        trace_thermal_power_cpu_limit(&cpufreq_device->allowed_cpus,
                                      target_freq, *state, power);
        return 0;
}
 
static u32 cpu_freq_to_power(struct cpufreq_cooling_device *cpufreq_cdev,
                             u32 freq)
{
        int i;
 
        for (i = cpufreq_cdev->max_level - 1; i >= 0; i--) {
                if (freq > cpufreq_cdev->em->table[i].frequency)
                        break;
        }
        // 查表获取
        return cpufreq_cdev->em->table[i + 1].power;
}

遍历了一下cpufrep_cdev里的em->table，这个table蕴含了freq和power的对应关系，这个table是跟芯片密切相关的，往往在出厂的时候就已经预制好了。

Linux Thermal框架-CSDN博客