目錄

1、thermal簡介

2、thermal_core分析

2.1 zone_device注冊相關接口

2.1.1 關鍵結構體

2.1.2 接口

2.2 Cooling_device注冊相關接口

2.2.1關鍵結構體

2.2.2 接口

2.3 Governors注冊相關接口

2.4 關于critial事件和非critial事件的處理流程

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1、thermal簡介

? ? ?thermal模塊主要負責溫度控制，溫度低時想辦法升溫，溫度高時想辦法降溫，甚至復位系統。Linux kernel有個通用的思想就是抽象分層，比如把該子系統所有資源和信息綜合在一起的一層叫core層，不同的設備的操作叫device層，對設備的操作的屏蔽層叫driver層或者governor。同樣thermal子系統也是采用了該思想：核心為 thermal_core，可以獲取溫度的設備抽象為 thermal_zone_device, 如Temp Sensor、NTC(板上的熱敏電阻)等。控制溫度的設備抽象為 thermal_cooling_device, 如風扇、CPU、DDR、GPU等。溫控策略抽象為 thermal_governor，比如 step_wise、bang_bang 等。

? ? ? ?thermal_cooling_device 對應系統實施冷卻措施的驅動，是溫控的執行者。cooling device 維護一個 cooling 等級，即 state，一般 state 越高即系統的冷卻需求越高。cooling device 根據不同等級的冷卻需求進行冷卻行為。cooling device 只根據 state 進行冷卻操作，是實施者，而 state 的計算由 thermal governor 完成。結構 struct cpufreq_cooling_device 和 struct devfreq_cooling_device 作為對 thermal_cooling_device 的擴展，分別主要在 cpufreq_cooling.c 和 devfreq_cooling.c?中使用。

2、thermal_core分析

? ? ? ?thermal_core作為thermal的核心部分，負責把governor\cool device\zone_device關聯在一起，因此thermal_core就需要提供注冊接口和作為記錄的全局變量來記錄注冊的信息：

2.1 zone_device注冊相關接口

2.1.1 關鍵結構體

/*** struct thermal_zone_device - structure for a thermal zone* @id: unique id number for each thermal zone* @type: the thermal zone device type* @device: &struct device for this thermal zone* @trip_temp_attrs: attributes for trip points for sysfs: trip temperature* @trip_type_attrs: attributes for trip points for sysfs: trip type* @trip_hyst_attrs: attributes for trip points for sysfs: trip hysteresis* @mode: current mode of this thermal zone* @devdata: private pointer for device private data* @trips: number of trip points the thermal zone supports* @trips_disabled; bitmap for disabled trips* @passive_delay_jiffies: number of jiffies to wait between polls when* performing passive cooling.* @polling_delay_jiffies: number of jiffies to wait between polls when* checking whether trip points have been crossed (0 for* interrupt driven systems)* @temperature: current temperature. This is only for core code,* drivers should use thermal_zone_get_temp() to get the* current temperature* @last_temperature: previous temperature read* @emul_temperature: emulated temperature when using CONFIG_THERMAL_EMULATION* @passive: 1 if you've crossed a passive trip point, 0 otherwise.* @prev_low_trip: the low current temperature if you've crossed a passivetrip point.* @prev_high_trip: the above current temperature if you've crossed apassive trip point.* @need_update: if equals 1, thermal_zone_device_update needs to be invoked.* @ops: operations this &thermal_zone_device supports* @tzp: thermal zone parameters* @governor: pointer to the governor for this thermal zone* @governor_data: private pointer for governor data* @thermal_instances: list of &struct thermal_instance of this thermal zone* @ida: &struct ida to generate unique id for this zone's cooling* devices* @lock: lock to protect thermal_instances list* @node: node in thermal_tz_list (in thermal_core.c)* @poll_queue: delayed work for polling* @notify_event: Last notification event*/ struct thermal_zone_device {int id;char type[THERMAL_NAME_LENGTH];struct device device;struct attribute_group trips_attribute_group;struct thermal_attr *trip_temp_attrs;struct thermal_attr *trip_type_attrs;struct thermal_attr *trip_hyst_attrs;enum thermal_device_mode mode;void *devdata;int trips;unsigned long trips_disabled; /* bitmap for disabled trips */unsigned long passive_delay_jiffies;unsigned long polling_delay_jiffies;int temperature;int last_temperature;int emul_temperature;int passive;int prev_low_trip;int prev_high_trip;atomic_t need_update;struct thermal_zone_device_ops *ops;struct thermal_zone_params *tzp;struct thermal_governor *governor;void *governor_data;struct list_head thermal_instances;struct ida ida;struct mutex lock;struct list_head node;struct delayed_work poll_queue;enum thermal_notify_event notify_event; };

2.1.2 接口

1、thermal_zone_device_register：zone_device注冊接口，需要注冊時需要調用該接口來注冊。該接口中主要實現以下功能：

1）給zone_device賦值critical接口，再溫度過高時，critical接口負責重啟系統

2）關聯上匹配的governor

3）把該zone_device添加到thermal_tz_list中

4）給該zone_device綁定上相關的cooling_device

5）創建zone_device的溫度監控任務

2、thermal_zone_device_unregister：zone_device去注冊接口，需要去注冊時需要調用該接口來注冊。該接口實現的主要功能如下：

1）device從thermal_tz_list中刪除

2）對應任務刪除

3）對應的governor置空

2.2 Cooling_device注冊相關接口

2.2.1關鍵結構體

struct thermal_cooling_device_ops {int (*get_max_state) (struct thermal_cooling_device *, unsigned long *);int (*get_cur_state) (struct thermal_cooling_device *, unsigned long *);int (*set_cur_state) (struct thermal_cooling_device *, unsigned long);int (*get_requested_power)(struct thermal_cooling_device *, u32 *);int (*state2power)(struct thermal_cooling_device *, unsigned long, u32 *);int (*power2state)(struct thermal_cooling_device *, u32, unsigned long *); };struct thermal_cooling_device {int id;char *type;struct device device;struct device_node *np;void *devdata;void *stats;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; };

2.2.2 接口

1、thermal_cooling_device_register：cooling_device注冊接口，cooling_device_ops有3個非常重要的接口，分別是get_max_state、get_cur_state、set_cur_state，分別用于獲取最大狀態、獲取當前狀態、設置當前狀態，關于state，前邊第一節我們介紹了，就不再贅述。該接口實現的主要功能有：

1）添加該device到thermal_cdev_list中

2）Cooling_device與zone_device綁定

3）調用thermal_zone_device_update來更新溫度及做對應處理

2、thermal_cooling_device_unregister：與thermal_cooling_device_register互為逆操作。

實現的主要功能有：

1）從hermal_cdev_list中刪除該device

2）與zone device解綁定

2.3 Governors注冊相關接口

? ? ? ?Thermal的governor都是通過THERMAL_GOVERNOR_DECLARE定義到了__thermal_table_entry_這段空間內，然后在thermal core初始化時通過調用thermal_register_governors來注冊到thermal_governor_list鏈表中。

thermal_init->thermal_register_governors->?thermal_set_governor(和zone device關聯上)

2.4 關于critial事件和非critial事件的處理流程

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