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Linux Thermal Framework分析及实施

發布時間：2023/12/16 linux 37 豆豆

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Linux Thermal Framework分析及實施

關鍵詞：Zone、Cooling、Governor、Step Wise、Fair Share、trip等等。

Linux Thermal的目的是控制系統運行過程中采樣點溫度，避免溫度過高造成器件損壞，確保芯片長期穩定工作。

整個Thermal框架可以分為四部分：

Thermal Driver負責將獲取溫度設備，注冊成struct?thermal_zone_device，比如Temp Sensor、NTC等。
Thermal Governor則負責如何控制溫度，注冊成struct?thermal_governor，比如Step Wise、Bang Bang等等。
Thermal Cooling負責將控制溫度設備，注冊成struct?thermal_cooling_device，比如風扇、CPU、DDR、GPU等。
Thermal Core則是Thermal Driver、Thermal Governor、Thermal Cooling的粘合劑，同時提供了用戶空間sysfs節點等通用功能。

所以Thermal的工作流程是通過Thermal Driver獲取溫度，然后經過Thermal Governor決策，最后通過Thermal Cooling執行溫度控制。

下面首先從總體詳細分析Thermal框架以及數據結構、API(1. Thermal框架分析)，然后分別分析Thermal Driver實例(2. Thermal Driver實例)、Thermal Governor(Step Wise和Fair Share)(3. Thermal Governor分析)、以及Thermal Cooling實例(4. Thermal Cooling實例)。

最后將這些內容串起來，分析Thermal是如何控制溫度的。

1. Thermal框架分析

1.1 Thermal數據結構

struct thermal_zone_device是對獲取溫度設備的抽象，成員ops是對該Thermal Zone操作的抽象；governor是該Thermal Zone所使用的調溫策略；thermal_instances是該Thermal Zone下的Cooling Device列表。

struct thermal_zone_device {int id;char type[THERMAL_NAME_LENGTH];struct device device;struct thermal_attr *trip_temp_attrs;struct thermal_attr *trip_type_attrs;struct thermal_attr *trip_hyst_attrs;void *devdata;int trips;---------------------------------------------------------thermal zone支持的trip數目。unsigned long trips_disabled; /* bitmap for disabled trips */int passive_delay;int polling_delay;-------------------------------------------------輪詢讀取溫度的建個，0表示采用中斷形式。int temperature;---------------------------------------------------當前溫度。int last_temperature;----------------------------------------------最近一次溫度。int emul_temperature;int passive;int prev_low_trip;int prev_high_trip;unsigned int forced_passive;atomic_t need_update;struct thermal_zone_device_ops *ops;------------------------------當前thermal zone操作函數集。struct thermal_zone_params *tzp;----------------------------------當前thermal zone參數。struct thermal_governor *governor;void *governor_data;struct list_head thermal_instances;-------------------------------當前thermal zone上thermal_instances列表。struct idr idr;struct mutex lock;struct list_head node;struct delayed_work poll_queue;enum thermal_notify_event notify_event; };struct thermal_zone_device_ops {int (*bind) (struct thermal_zone_device *,struct thermal_cooling_device *);------------------------將cooling device綁定到thermal zone中，兩者通過struct thermal_instances在thermal_zone_bind_cooling_device()中綁定。int (*unbind) (struct thermal_zone_device *,struct thermal_cooling_device *);int (*get_temp) (struct thermal_zone_device *, int *);int (*set_trips) (struct thermal_zone_device *, int, int);int (*get_mode) (struct thermal_zone_device *,enum thermal_device_mode *);int (*set_mode) (struct thermal_zone_device *,enum thermal_device_mode);int (*get_trip_type) (struct thermal_zone_device *, int,enum thermal_trip_type *);int (*get_trip_temp) (struct thermal_zone_device *, int, int *);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);int (*get_trend) (struct thermal_zone_device *, int,enum thermal_trend *);int (*notify) (struct thermal_zone_device *, int,enum thermal_trip_type); };struct thermal_bind_params {struct thermal_cooling_device *cdev;int weight;int trip_mask;unsigned long *binding_limits;int (*match) (struct thermal_zone_device *tz,struct thermal_cooling_device *cdev); };struct thermal_zone_params {char governor_name[THERMAL_NAME_LENGTH];bool no_hwmon;int num_tbps; /* Number of tbp entries */struct thermal_bind_params *tbp; ...int slope;int offset; };struct thermal_zone_of_device_ops {int (*get_temp)(void *, int *);int (*get_trend)(void *, int, enum thermal_trend *);int (*set_trips)(void *, int, int);int (*set_emul_temp)(void *, int);int (*set_trip_temp)(void *, int, int); };

struct thermal_cooling_device是對降溫設備的抽象，對風扇設備就是不同的轉速，對CPU、DDR、GPU就是不同的電壓或者頻率。

struct thermal_cooling_device_ops是Cooling Device操作函數集，其中set_cur_state()是對設備進行溫度控制。

struct thermal_cooling_device {int id;char type[THERMAL_NAME_LENGTH];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 {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); ... }

strcut thermal_governor是對溫控策略的抽象，也就是根據Thermal Zone的trip來選擇Thermal Cooling設備的行為。比如，溫度越高風扇轉速越快；溫度越高CPU運行在更低電壓和頻率上。

struct thermal_governor {char name[THERMAL_NAME_LENGTH];int (*bind_to_tz)(struct thermal_zone_device *tz);---------------------將一個governor綁定到thermal zone得一個trip上。void (*unbind_from_tz)(struct thermal_zone_device *tz);----------------將一個governor從thermal zone解綁。int (*throttle)(struct thermal_zone_device *tz, int trip);-------------根據trip遍歷當前thermal zone下所有的cooling device執行溫控策略。struct list_head governor_list;-------------------------------------thermal_governor_list上的一個列表元素。 };

所有的策略選擇都是通過throttle()函數進行的，不同的Governor的區別也主要在這里。內核已經實現了Step Wise、User等等，并且還在演進中。

通過struct thermal_instances可以將thermal zone和thermal cooling設備綁定起來。

struct thermal_instance {int id;char name[THERMAL_NAME_LENGTH];struct thermal_zone_device *tz;-------------------------------------------綁定的thermal zone。struct thermal_cooling_device *cdev;--------------------------------------綁定的thermal cooling設備。int trip;-----------------------------------------------------------------對應的thermal zone的trip。bool initialized;unsigned long upper; /* Highest cooling state for this trip point */---cooling設備的最高降溫狀態。unsigned long lower; /* Lowest cooling state for this trip point */----cooling設備最低降溫狀態。unsigned long target; /* expected cooling state */---------------------cooling設備的當前狀態，也是thermal_cooling_device_ops->set_cur_state()設置后的值。char attr_name[THERMAL_NAME_LENGTH];struct device_attribute attr;char weight_attr_name[THERMAL_NAME_LENGTH];struct device_attribute weight_attr;struct list_head tz_node; /* node in tz->thermal_instances */-------------thermal_zone_device->thermal_instances上的節點。struct list_head cdev_node; /* node in cdev->thermal_instances */---------thermal_cooling_device->thermal_instances上的節點。unsigned int weight; /* The weight of the cooling device */ }

thermal_device_mode表示當前的thermal zone是否使能。

thermal_trip_type表示thermal zone的當前trip類型，其中ACTIVE和PASSIVE屬于non-critical類型，交由Governor進行處理；HOT和CRITICAL屬于critical類型，其中CRITICAL會執行orderly_poweroff()。

thermal_trend表示thermal zone的溫度趨勢，是平緩、上升、下降還是跳躍式的，這就給Governor選擇trip提供依據。

enum thermal_device_mode {THERMAL_DEVICE_DISABLED = 0,THERMAL_DEVICE_ENABLED, };enum thermal_trip_type {THERMAL_TRIP_ACTIVE = 0,THERMAL_TRIP_PASSIVE,THERMAL_TRIP_HOT,THERMAL_TRIP_CRITICAL, };enum thermal_trend {THERMAL_TREND_STABLE, /* temperature is stable */-----------------------表示溫度平穩。THERMAL_TREND_RAISING, /* temperature is raising */---------------------表示當前溫度趨勢是升高的。THERMAL_TREND_DROPPING, /* temperature is dropping */-------------------表示當前溫度趨勢是降低的。THERMAL_TREND_RAISE_FULL, /* apply highest cooling action */------------直接應用upper對應的trip。THERMAL_TREND_DROP_FULL, /* apply lowest cooling action */--------------直接應用lower對應的trip。 };/* Thermal notification reason */ enum thermal_notify_event {THERMAL_EVENT_UNSPECIFIED, /* Unspecified event */THERMAL_EVENT_TEMP_SAMPLE, /* New Temperature sample */THERMAL_TRIP_VIOLATED, /* TRIP Point violation */THERMAL_TRIP_CHANGED, /* TRIP Point temperature changed */THERMAL_DEVICE_DOWN, /* Thermal device is down */THERMAL_DEVICE_UP, /* Thermal device is up after a down event */THERMAL_DEVICE_POWER_CAPABILITY_CHANGED, /* power capability changed */ }

1.2 Thermal Core APIs

Thermal core是Thermal Zone、Thermal Cooling、ThermalGovernor的粘合劑。

通過Thermal core提供的API，將這三者相互關聯起來；從Thermal Zone設備獲取溫度，選擇對應的Thermal Governor，Thermal Governor設置Thermal Cooling的狀態，進而達到控制溫度的目的。

通過thermal_zone_device_register()注冊thermal zone設備，創建一系列sysfs節點，并且和governor、cooling進行綁定。

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;if (type && strlen(type) >= THERMAL_NAME_LENGTH)return ERR_PTR(-EINVAL);if (trips > THERMAL_MAX_TRIPS || trips < 0 || mask >> trips)return ERR_PTR(-EINVAL);if (!ops)return ERR_PTR(-EINVAL);if (trips > 0 && (!ops->get_trip_type || !ops->get_trip_temp))return ERR_PTR(-EINVAL);tz = kzalloc(sizeof(struct thermal_zone_device), GFP_KERNEL);if (!tz)return ERR_PTR(-ENOMEM);INIT_LIST_HEAD(&tz->thermal_instances);------------------------------初始化thermal_instances鏈表，放置struct thermal_instances實例。通過thermal_instances可以關聯thermal zone和thermal cooling。idr_init(&tz->idr);mutex_init(&tz->lock);result = get_idr(&thermal_tz_idr, &thermal_idr_lock, &tz->id);if (result) {kfree(tz);return ERR_PTR(result);}strlcpy(tz->type, type ? : "", sizeof(tz->type));tz->ops = ops;tz->tzp = tzp;tz->device.class = &thermal_class;------------------------------------創建的設備會在/sys/class/thermal下面有個鏈接。tz->devdata = devdata;tz->trips = trips;tz->passive_delay = passive_delay;tz->polling_delay = polling_delay;/* A new thermal zone needs to be updated anyway. */atomic_set(&tz->need_update, 1);dev_set_name(&tz->device, "thermal_zone%d", tz->id);result = device_register(&tz->device);--------------------------------創建/sys/devices/virtual/thermal/thermal_zone*設備。if (result) {release_idr(&thermal_tz_idr, &thermal_idr_lock, tz->id);kfree(tz);return ERR_PTR(result);}/* sys I/F */---------------------------------------------------------分別創建type、temp、mode、trip等sysfs節點。if (type) {result = device_create_file(&tz->device, &dev_attr_type);if (result)goto unregister;} ...result = create_trip_attrs(tz, mask);-----------------------為每個trip創建trip_point_*_temp/hyst/type節點。if (result)goto unregister; ... /* Update 'this' zone's governor information */mutex_lock(&thermal_governor_lock);if (tz->tzp)-------------------------------------------------如果指定thermal zone的governor則通過__find_governor()選定；否則使用默認def_governor。governor = __find_governor(tz->tzp->governor_name);elsegovernor = def_governor;result = thermal_set_governor(tz, governor);-----------------將governor綁定到tz上，優先使用bind_to_tz()執行綁定；否則直接指定tz->governor為governor。if (result) {mutex_unlock(&thermal_governor_lock);goto unregister;}mutex_unlock(&thermal_governor_lock);if (!tz->tzp || !tz->tzp->no_hwmon) {result = thermal_add_hwmon_sysfs(tz);if (result)goto unregister;}mutex_lock(&thermal_list_lock);list_add_tail(&tz->node, &thermal_tz_list);------------------------將當前thermal zone加入到thermal_tz_list列表上。mutex_unlock(&thermal_list_lock);/* Bind cooling devices for this zone */bind_tz(tz);-------------------------------------------------------調用tz->ops->bind()將thermal_cdev_list上的cooling設備綁定到tz上。INIT_DELAYED_WORK(&(tz->poll_queue), thermal_zone_device_check);thermal_zone_device_reset(tz);-------------------------------------對thermal zone的溫度等復位。/* 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;unregister:release_idr(&thermal_tz_idr, &thermal_idr_lock, tz->id);device_unregister(&tz->device);return ERR_PTR(result); }static int thermal_set_governor(struct thermal_zone_device *tz,struct thermal_governor *new_gov) {int ret = 0;if (tz->governor && tz->governor->unbind_from_tz)tz->governor->unbind_from_tz(tz);------------------------------先調用當前governor進行unbind()。if (new_gov && new_gov->bind_to_tz) {ret = new_gov->bind_to_tz(tz);---------------------------------使用當前governor進行bind()。if (ret) {bind_previous_governor(tz, new_gov->name);return ret;}}tz->governor = new_gov;--------------------------------------------更新tz->governor。return ret; }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 there is ops->bind, try to use ops->bind */if (tz->ops->bind) {list_for_each_entry(pos, &thermal_cdev_list, node) {-----------遍歷thermal_cdev_list的cooling設備，然后和當前thermal zone進行綁定。ret = tz->ops->bind(tz, pos);if (ret)print_bind_err_msg(tz, pos, ret);}goto exit;} ... exit:mutex_unlock(&thermal_list_lock); }static void thermal_zone_device_check(struct work_struct *work) {struct thermal_zone_device *tz = container_of(work, structthermal_zone_device,poll_queue.work);thermal_zone_device_update(tz, THERMAL_EVENT_UNSPECIFIED);

?thermal_zone_device_unregister()則執行相反的操作，將thermal zone從thermal_tz_list上摘除，并且和cooling設備去綁定，以及刪除一系列sysfs節點。

void thermal_zone_device_unregister(struct thermal_zone_device *tz) {int i;const struct thermal_zone_params *tzp;struct thermal_cooling_device *cdev;struct thermal_zone_device *pos = NULL;if (!tz)return;tzp = tz->tzp;mutex_lock(&thermal_list_lock);list_for_each_entry(pos, &thermal_tz_list, node)if (pos == tz)break;if (pos != tz) {/* thermal zone device not found */mutex_unlock(&thermal_list_lock);return;}list_del(&tz->node);/* Unbind all cdevs associated with 'this' thermal zone */list_for_each_entry(cdev, &thermal_cdev_list, node) {if (tz->ops->unbind) {tz->ops->unbind(tz, cdev);continue;} ...} ...return;

thermal_cooling_device_register()創建cooling設備并放入thermal_cdev_list中，以及相關sysfs節點，并將cooling設備和thermal zone綁定。

thermal_cooling_device_unregister()則進行相反的操作。

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);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);cdev->np = np;cdev->ops = ops;cdev->updated = false;cdev->device.class = &thermal_class;---------------------------------cooling設備同樣會在/sys/class/thermal下創建鏈接。cdev->device.groups = cooling_device_attr_groups;--------------------創建cur_state、max_state、type三個sysfs節點。cdev->devdata = devdata;dev_set_name(&cdev->device, "cooling_device%d", cdev->id);result = device_register(&cdev->device);-----------------------------創建/sys/devices/virtual/thermal/cooling_device*設備節點。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 */mutex_lock(&thermal_list_lock);list_add(&cdev->node, &thermal_cdev_list);---------------------------將設備放入thermal_cdev_list設備鏈表。mutex_unlock(&thermal_list_lock);/* Update binding information for 'this' new cdev */bind_cdev(cdev);-----------------------------------------------------遍歷thermal_tz_list，將cdev綁定到上面的thermal zone。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,THERMAL_EVENT_UNSPECIFIED);mutex_unlock(&thermal_list_lock);return cdev; }void thermal_cooling_device_unregister(struct thermal_cooling_device *cdev) {int i;const struct thermal_zone_params *tzp;struct thermal_zone_device *tz;struct thermal_cooling_device *pos = NULL;if (!cdev)return;mutex_lock(&thermal_list_lock);list_for_each_entry(pos, &thermal_cdev_list, node)if (pos == cdev)break;if (pos != cdev) {/* thermal cooling device not found */mutex_unlock(&thermal_list_lock);return;}list_del(&cdev->node);/* Unbind all thermal zones associated with 'this' cdev */list_for_each_entry(tz, &thermal_tz_list, node) {if (tz->ops->unbind) {tz->ops->unbind(tz, cdev);continue;}if (!tz->tzp || !tz->tzp->tbp)continue;tzp = tz->tzp;for (i = 0; i < tzp->num_tbps; i++) {if (tzp->tbp[i].cdev == cdev) {__unbind(tz, tzp->tbp[i].trip_mask, cdev);tzp->tbp[i].cdev = NULL;}}}mutex_unlock(&thermal_list_lock);if (cdev->type[0])device_remove_file(&cdev->device, &dev_attr_cdev_type);device_remove_file(&cdev->device, &dev_attr_max_state);device_remove_file(&cdev->device, &dev_attr_cur_state);release_idr(&thermal_cdev_idr, &thermal_idr_lock, cdev->id);device_unregister(&cdev->device);return;

thermal_register_governor()首先判斷thermal_governor_list上是否有同名governor，然后更新thermal_tz_list上未指定governor的thermal zone。

thermal_unregister_governor()則相反，將governor和thermal zone調用unbind_from_tz()并置空；最后從thermal_go上摘除。

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) {--------------------檢查此governor是否已經在thermal_governor_list中，如果不在則加入thermal_governor_list。并且判斷是否為def_governor。err = 0;list_add(&governor->governor_list, &thermal_governor_list);if (!def_governor && !strncmp(governor->name,DEFAULT_THERMAL_GOVERNOR, THERMAL_NAME_LENGTH))def_governor = governor;}mutex_lock(&thermal_list_lock);list_for_each_entry(pos, &thermal_tz_list, node) {if (pos->governor)--------------------------------------------如果thermal zone已經制定governor，則跳過。continue;name = pos->tzp->governor_name;if (!strncasecmp(name, governor->name, THERMAL_NAME_LENGTH)) {int ret;ret = thermal_set_governor(pos, governor);----------------給當前thermal zone制定governor。if (ret)dev_err(&pos->device,"Failed to set governor %s for thermal zone %s: %d\n",governor->name, pos->type, ret);}}mutex_unlock(&thermal_list_lock);mutex_unlock(&thermal_governor_lock);return err; }void thermal_unregister_governor(struct thermal_governor *governor) {struct thermal_zone_device *pos;if (!governor)return;mutex_lock(&thermal_governor_lock);if (__find_governor(governor->name) == NULL)goto exit;mutex_lock(&thermal_list_lock);list_for_each_entry(pos, &thermal_tz_list, node) {if (!strncasecmp(pos->governor->name, governor->name,THERMAL_NAME_LENGTH))thermal_set_governor(pos, NULL);}mutex_unlock(&thermal_list_lock);list_del(&governor->governor_list); exit:mutex_unlock(&thermal_governor_lock);return;

thermal_zone_bind_cooling_device()通過創建thermal_instances設備將Thermal Zone和Thermal Cooling綁定，這樣Thermal Zone就可以根據溫度處理Thermal Cooling設備。

thermal_zone_unbind_cooling_device() 則將關聯Thermal Zone和Thermal Cooling的thermal_instances從兩者的鏈表上摘除。

int thermal_zone_bind_cooling_device(struct thermal_zone_device *tz,int trip,struct thermal_cooling_device *cdev,unsigned long upper, unsigned long lower,unsigned int weight) {struct thermal_instance *dev;struct thermal_instance *pos;struct thermal_zone_device *pos1;struct thermal_cooling_device *pos2;unsigned long max_state;int result, ret;if (trip >= tz->trips || (trip < 0 && trip != THERMAL_TRIPS_NONE))return -EINVAL;list_for_each_entry(pos1, &thermal_tz_list, node) {if (pos1 == tz)break;}list_for_each_entry(pos2, &thermal_cdev_list, node) {if (pos2 == cdev)break;}if (tz != pos1 || cdev != pos2)return -EINVAL;ret = cdev->ops->get_max_state(cdev, &max_state);----------------------從Cooling設備操作函數get_max_state()獲取max_state，進而決定thermal_instances的lower和upper范圍。if (ret)return ret;/* lower default 0, upper default max_state */lower = lower == THERMAL_NO_LIMIT ? 0 : lower;upper = upper == THERMAL_NO_LIMIT ? max_state : upper;if (lower > upper || upper > max_state)return -EINVAL;dev =kzalloc(sizeof(struct thermal_instance), GFP_KERNEL);if (!dev)return -ENOMEM;dev->tz = tz;dev->cdev = cdev;dev->trip = trip;dev->upper = upper;dev->lower = lower;dev->target = THERMAL_NO_TARGET;dev->weight = weight;result = get_idr(&tz->idr, &tz->lock, &dev->id);if (result)goto free_mem;sprintf(dev->name, "cdev%d", dev->id);result =sysfs_create_link(&tz->device.kobj, &cdev->device.kobj, dev->name);------cdevx連接到cooling_devicex。if (result)goto release_idr;sprintf(dev->attr_name, "cdev%d_trip_point", dev->id);-----------------------創建cdevx_trip_point和cdevx_weight節點。sysfs_attr_init(&dev->attr.attr);dev->attr.attr.name = dev->attr_name;dev->attr.attr.mode = 0444;dev->attr.show = thermal_cooling_device_trip_point_show;result = device_create_file(&tz->device, &dev->attr);if (result)goto remove_symbol_link;sprintf(dev->weight_attr_name, "cdev%d_weight", dev->id);sysfs_attr_init(&dev->weight_attr.attr);dev->weight_attr.attr.name = dev->weight_attr_name;dev->weight_attr.attr.mode = S_IWUSR | S_IRUGO;dev->weight_attr.show = thermal_cooling_device_weight_show;dev->weight_attr.store = thermal_cooling_device_weight_store;result = device_create_file(&tz->device, &dev->weight_attr);if (result)goto remove_trip_file;... }int thermal_zone_unbind_cooling_device(struct thermal_zone_device *tz,int trip,struct thermal_cooling_device *cdev) {struct thermal_instance *pos, *next;mutex_lock(&tz->lock);mutex_lock(&cdev->lock);list_for_each_entry_safe(pos, next, &tz->thermal_instances, tz_node) {if (pos->tz == tz && pos->trip == trip && pos->cdev == cdev) {list_del(&pos->tz_node);list_del(&pos->cdev_node);mutex_unlock(&cdev->lock);mutex_unlock(&tz->lock);goto unbind;}}mutex_unlock(&cdev->lock);mutex_unlock(&tz->lock);return -ENODEV;unbind:device_remove_file(&tz->device, &pos->weight_attr);device_remove_file(&tz->device, &pos->attr);sysfs_remove_link(&tz->device.kobj, pos->name);release_idr(&tz->idr, &tz->lock, pos->id);kfree(pos);return 0;

thermal_zone_device_update()一般由Thermal驅動調用，有可能是polling或者中斷觸發。

然后更新當前Thermal Zone的溫度，最后根據溫度值通過handle_thermal_trip()進行處理。

monitor_thermal_zone()根據passive和polling的設置決定是否啟動thermal_zone_device->pool_queue這個delayed_work。

整個polling流程由thermal_zone_device_update()觸發，依次流程為：handle_thermal_trip()中啟動monitor_thermal_zone()，monitor_thermal_zone()中調用mod_delayed_work()進行poll_queue延時值的更新。如果thermal zone有多個trip，poll_queue延時值可能被多次更新。poll_queue放入system_freezable_wq后，達到時間后調用thermal_zone_device_check()，進而調用thermal_zone_device_update()完成周期性循環。

void thermal_zone_device_update(struct thermal_zone_device *tz,enum thermal_notify_event event) {int count;if (atomic_read(&in_suspend))return;if (!tz->ops->get_temp)return;update_temperature(tz);thermal_zone_set_trips(tz);tz->notify_event = event;for (count = 0; count < tz->trips; count++)handle_thermal_trip(tz, count); }static void update_temperature(struct thermal_zone_device *tz) {int temp, ret;ret = thermal_zone_get_temp(tz, &temp);if (ret) {if (ret != -EAGAIN)dev_warn(&tz->device,"failed to read out thermal zone (%d)\n",ret);return;}mutex_lock(&tz->lock);tz->last_temperature = tz->temperature;tz->temperature = temp;mutex_unlock(&tz->lock);trace_thermal_temperature(tz);if (tz->last_temperature == THERMAL_TEMP_INVALID)dev_dbg(&tz->device, "last_temperature N/A, current_temperature=%d\n",tz->temperature);elsedev_dbg(&tz->device, "last_temperature=%d, current_temperature=%d\n",tz->last_temperature, tz->temperature); }void thermal_zone_set_trips(struct thermal_zone_device *tz) {int low = -INT_MAX;int high = INT_MAX;int trip_temp, hysteresis;int i, ret;mutex_lock(&tz->lock);if (!tz->ops->set_trips || !tz->ops->get_trip_hyst)goto exit;for (i = 0; i < tz->trips; i++) {int trip_low;tz->ops->get_trip_temp(tz, i, &trip_temp);tz->ops->get_trip_hyst(tz, i, &hysteresis);trip_low = trip_temp - hysteresis;if (trip_low < tz->temperature && trip_low > low)low = trip_low;if (trip_temp > tz->temperature && trip_temp < high)high = trip_temp;}/* No need to change trip points */if (tz->prev_low_trip == low && tz->prev_high_trip == high)goto exit;tz->prev_low_trip = low;tz->prev_high_trip = high;dev_dbg(&tz->device,"new temperature boundaries: %d < x < %d\n", low, high);ret = tz->ops->set_trips(tz, low, high);if (ret)dev_err(&tz->device, "Failed to set trips: %d\n", ret);exit:mutex_unlock(&tz->lock); }static void handle_thermal_trip(struct thermal_zone_device *tz, int trip) {enum thermal_trip_type type;/* Ignore disabled trip points */if (test_bit(trip, &tz->trips_disabled))return;tz->ops->get_trip_type(tz, trip, &type);if (type == THERMAL_TRIP_CRITICAL || type == THERMAL_TRIP_HOT)handle_critical_trips(tz, trip, type);elsehandle_non_critical_trips(tz, trip, type);/** Alright, we handled this trip successfully.* So, start monitoring again.*/monitor_thermal_zone(tz); }static void handle_critical_trips(struct thermal_zone_device *tz,int trip, enum thermal_trip_type trip_type) {int trip_temp;tz->ops->get_trip_temp(tz, trip, &trip_temp);/* If we have not crossed the trip_temp, we do not care. */if (trip_temp <= 0 || tz->temperature < trip_temp)return;trace_thermal_zone_trip(tz, trip, trip_type);if (tz->ops->notify)tz->ops->notify(tz, trip, trip_type);if (trip_type == THERMAL_TRIP_CRITICAL) {dev_emerg(&tz->device,"critical temperature reached(%d C),shutting down\n",tz->temperature / 1000);orderly_poweroff(true);} }static void handle_non_critical_trips(struct thermal_zone_device *tz,int trip, enum thermal_trip_type trip_type) {tz->governor ? tz->governor->throttle(tz, trip) :def_governor->throttle(tz, trip); }static void monitor_thermal_zone(struct thermal_zone_device *tz) {mutex_lock(&tz->lock);if (tz->passive)-----------------------------------分別設置passive和polling兩種延時工作。thermal_zone_device_set_polling(tz, tz->passive_delay);else if (tz->polling_delay)thermal_zone_device_set_polling(tz, tz->polling_delay);elsethermal_zone_device_set_polling(tz, 0);mutex_unlock(&tz->lock); }static void thermal_zone_device_set_polling(struct thermal_zone_device *tz,int delay) {if (delay > 1000)----------------------------------將poll_queue放入system_freezable_wq工作隊列上，多次調用mod_delayed_work()在超時前只有最后一次生效。mod_delayed_work(system_freezable_wq, &tz->poll_queue,round_jiffies(msecs_to_jiffies(delay)));else if (delay)mod_delayed_work(system_freezable_wq, &tz->poll_queue,msecs_to_jiffies(delay));elsecancel_delayed_work(&tz->poll_queue);----------如果delay為0，則取消poll_queue延時工作。

thermal_cdev_update()是由Governor調用進行cooling device設置。

void thermal_cdev_update(struct thermal_cooling_device *cdev) {struct thermal_instance *instance;unsigned long target = 0;mutex_lock(&cdev->lock);/* cooling device is updated*/if (cdev->updated) {mutex_unlock(&cdev->lock);return;}/* Make sure cdev enters the deepest cooling state */list_for_each_entry(instance, &cdev->thermal_instances, cdev_node) {----------遍歷當前cooling device上所有的thermal zone。dev_dbg(&cdev->device, "zone%d->target=%lu\n",instance->tz->id, instance->target);if (instance->target == THERMAL_NO_TARGET)continue;if (instance->target > target)target = instance->target;---------------------------------------------確保cooling設備選擇最高cooling狀態，然后調用cooling設備的set_cur_state()進行降溫。}cdev->ops->set_cur_state(cdev, target);cdev->updated = true;mutex_unlock(&cdev->lock);trace_cdev_update(cdev, target);dev_dbg(&cdev->device, "set to state %lu\n", target);

1.3 Thermal初始化

thermal_init()在內核fs_initcall()階段調用，進行governor、thermal_class、Generic Netlink注冊等操作。

static int __init thermal_init(void) {int result;result = thermal_register_governors();---------------注冊平臺支持的所有governor。if (result)goto error;result = class_register(&thermal_class);-------------注冊thermal_class。if (result)goto unregister_governors;result = genetlink_init();---------------------------注冊Generic Netlink。if (result)goto unregister_class;...return result; }static void __exit thermal_exit(void) {unregister_pm_notifier(&thermal_pm_nb);of_thermal_destroy_zones();genetlink_exit();class_unregister(&thermal_class);thermal_unregister_governors();... }fs_initcall(thermal_init); module_exit(thermal_exit)

2. Thermal Driver實例

?下面首先簡單看一下Temp Sensor的硬件，然后分析DTS，最后分析驅動的實現。

2.1 Temp Sensor硬件

對Temp Sensor的配置可以通過APB BUS進行，包括兩個Temp Sensor，每個Temp Sensor中包括3個Trip觸發點設置，以及一個Alarm配置。

Trip達到后會觸發中斷，CPU的INTC收到中斷后，進行中斷處理；Alarm達到后直接導致CPU復位或者關閉PLL。

Temp Sensor默認使用32K時鐘，每32768個時鐘采樣一次。還可以根據情況選擇24M作為時鐘輸入。

一個重要工作就是根據實際情況，選定Trip溫度以及Alarm溫度。

另一個核心的工作就是確定如何根據Data寄存器的值計算出溫度值。這就需要計算兩個參數A和B。

通過其他測量手段讀出溫度值，以及當前溫度值下的DBN<11:0>。這獲取一系列數據之后，通過直線數據擬合，得出A和B的值。

2.2 Temp Sensor DTS

?DTS是對硬件的抽象，包括寄存器配置地址和范圍、中斷、3個trip溫度、一個alarm溫度。

sensor0: sensor0@0xfc20a000 {compatible = "vsi,dp1000-thermal";reg = <0xfc20a000 0x20>;interrupts = <38>;vsi,temp0 = <90>;vsi,temp1 = <95>;vsi,temp2 = <100>;vsi,alarm_temp = <120>;vsi,alarm_en;};

從DTS可以看出，通過配置不同trip和alarm的溫度，中斷觸發后，CPU會讀取溫度進行相應處理。

2.3 Temp Sensor驅動

Temp Sensor的驅動首先解析DTS，并進行iomem映射；然后注冊中斷以及下半部workqueue處理；再進行硬件設置；最后注冊thermal zone設備。

在設備正常工作中，根據配置的trip和alarm值觸發中斷，然后進行work處理；中間會用到struct thermal_zone_device_ops提供的成員函數獲取溫度、和cooling設備綁定等等操作。

2.3.1 Thermal Sensor注冊

static int dp1000_thermal_probe(struct platform_device *pdev) {struct dp1000_thermal_priv *priv;struct resource *res;int ret;priv = devm_kzalloc(&pdev->dev, sizeof(*priv), GFP_KERNEL);if (!priv)return -ENOMEM;res = platform_get_resource(pdev, IORESOURCE_MEM, 0);priv->reg_base = devm_ioremap_resource(&pdev->dev, res);if (IS_ERR(priv->reg_base))return PTR_ERR(priv->reg_base);if (device_property_read_u32(&pdev->dev, "vsi,temp0", &priv->temp0) < 0) {dev_dbg(&pdev->dev,"\"temp0\" property is missing, using default value.\n");priv->temp0 = 0;} ...INIT_DELAYED_WORK(&priv->work, dp1000_thermal_work);---------------------創建delayed_work，對應的處理函數是dp1000_thermal_work()。priv->irq = platform_get_irq(pdev, 0); ...ret = devm_request_irq(&pdev->dev, priv->irq,dp1000_thermal_interrupt, 0,dev_name(&pdev->dev), priv);-------------------------------irq注冊，中斷處理函數為dp1000_thermal_interrupt()。 ...dp1000_init_thermal(priv);------------------------------------------------硬件初始化。priv->zone = thermal_zone_device_register("dp1000_thermal", DP1000_THERMAL_TRIPS, 0,priv, &dp1000_thermal_zone_ops, NULL, 0, 0);-------Thermal Zone注冊。#ifdef DP1000_THERMAL_STUBif(priv->zone->id == 0)thermal_zone_0 = priv->zone;else if(priv->zone->id == 1)thermal_zone_1 = priv->zone;#endif ...return 0; }static int dp1000_thermal_remove(struct platform_device *pdev) {struct dp1000_thermal_priv *priv = dev_get_drvdata(&pdev->dev); ... return 0; }static const struct of_device_id dp1000_thermal_id_table[] = {{ .compatible = "vsi,dp1000-thermal" },-----------------------------------和dts匹配。{ } }; MODULE_DEVICE_TABLE(of, dp1000_thermal_id_table);static struct platform_driver dp1000_thermal_driver = {.probe = dp1000_thermal_probe,.remove = dp1000_thermal_remove,.driver = {.name = "dp1000_thermal",.of_match_table = dp1000_thermal_id_table,}, };module_platform_driver(dp1000_thermal_driver)

dp1000_thermal_zone_ops函數集是Thermal Sensor的核心，對Thermal Zone的操作都是通過調用這些函數實現的。

static struct thermal_zone_device_ops dp1000_thermal_zone_ops = {.bind = dp1000_thermal_bind,.unbind = dp1000_thermal_unbind,.get_trip_type = dp1000_thermal_get_trip_type,.get_trip_hyst = dp1000_thermal_get_trip_hyst,.get_temp = dp1000_thermal_get_temp,.set_trip_temp = dp1000_thermal_set_trip_temp,.get_trip_temp = dp1000_thermal_get_trip_temp,.get_crit_temp = dp1000_thermal_get_crit_temp, };

2.3.2 Thermal Driver中斷能觸發流程

當Thermal Sensor的溫度達到trip值時，會觸發中斷。

然后進入dp1000_thermal_interrupt()，在延時300ms進行dp1000_thermal_work()處理。

static irqreturn_t dp1000_thermal_interrupt(int irq, void *id) {struct dp1000_thermal_priv *priv = (struct dp1000_thermal_priv *)id;unsigned int status;if (status == 0)return IRQ_NONE;else {schedule_delayed_work(&priv->work, msecs_to_jiffies(300));}return IRQ_HANDLED; }static void dp1000_thermal_work(struct work_struct *work) {struct dp1000_thermal_priv *priv;priv = container_of(work, struct dp1000_thermal_priv, work.work);thermal_zone_device_update(priv->zone, THERMAL_EVENT_UNSPECIFIED);

最終的工作交給thermal_zone_device_update()進行，讀取溫度，根據溫度選擇trip。

->3. Thermal Governor分析

下面簡單分析兩個Governor：Step Wise和Fair Share。

3.1 Step Wise分析

首先看一下Step Wise的注冊。

static struct thermal_governor thermal_gov_step_wise = {.name = "step_wise",.throttle = step_wise_throttle, };int thermal_gov_step_wise_register(void) {return thermal_register_governor(&thermal_gov_step_wise); }void thermal_gov_step_wise_unregister(void) {thermal_unregister_governor(&thermal_gov_step_wise);

在handle_non_critical_trips()中，首先選用當前thermal zone的throttle()進行處理。

對于Step Wise governor來說，對外的接口只有step_wise_throttle()。

static int step_wise_throttle(struct thermal_zone_device *tz, int trip) {struct thermal_instance *instance;thermal_zone_trip_update(tz, trip);-----------------------------根據當前溫度和上次溫度對比，得到溫度趨勢；然后根據溫度趨勢得出Cooling設備對應的state。if (tz->forced_passive)thermal_zone_trip_update(tz, THERMAL_TRIPS_NONE);mutex_lock(&tz->lock);list_for_each_entry(instance, &tz->thermal_instances, tz_node)thermal_cdev_update(instance->cdev);------------------------遍歷cdev->thermal_instances選擇最深的cooling狀態。然后調用cdev->ops->set_cur_state()中。mutex_unlock(&tz->lock);return 0; }static void thermal_zone_trip_update(struct thermal_zone_device *tz, int trip) {int trip_temp;enum thermal_trip_type trip_type;enum thermal_trend trend;struct thermal_instance *instance;bool throttle = false;int old_target;if (trip == THERMAL_TRIPS_NONE) {trip_temp = tz->forced_passive;trip_type = THERMAL_TRIPS_NONE;} else {tz->ops->get_trip_temp(tz, trip, &trip_temp);tz->ops->get_trip_type(tz, trip, &trip_type);}trend = get_tz_trend(tz, trip);----------------------------------------根據當前溫度tz->temperature和tz->last_temperature對比，判定tend是STABLE/RAISING/DROPPING等中的一種。if (tz->temperature >= trip_temp) {throttle = true;---------------------------------------------------throttle為true表示需要節流，即降溫。trace_thermal_zone_trip(tz, trip, trip_type);}mutex_lock(&tz->lock);list_for_each_entry(instance, &tz->thermal_instances, tz_node) {if (instance->trip != trip)----------------------------------------相同trip不做處理。continue;old_target = instance->target;instance->target = get_target_state(instance, trend, throttle);----instance->target是將要設置到Cooling設備的狀態。 if (instance->initialized && old_target == instance->target)continue;/* Activate a passive thermal instance */if (old_target == THERMAL_NO_TARGET &&instance->target != THERMAL_NO_TARGET)update_passive_instance(tz, trip_type, 1);/* Deactivate a passive thermal instance */else if (old_target != THERMAL_NO_TARGET &&instance->target == THERMAL_NO_TARGET)update_passive_instance(tz, trip_type, -1);instance->initialized = true;mutex_lock(&instance->cdev->lock);instance->cdev->updated = false;------------------------------------updated為false表示Cooling設備需要更新狀態，在thermal_cdev_update()中會進行判斷。mutex_unlock(&instance->cdev->lock);}mutex_unlock(&tz->lock); }static unsigned long get_target_state(struct thermal_instance *instance,enum thermal_trend trend, bool throttle) {struct thermal_cooling_device *cdev = instance->cdev;unsigned long cur_state;unsigned long next_target;cdev->ops->get_cur_state(cdev, &cur_state);next_target = instance->target;dev_dbg(&cdev->device, "cur_state=%ld\n", cur_state);if (!instance->initialized) {if (throttle) {next_target = (cur_state + 1) >= instance->upper ?instance->upper :((cur_state + 1) < instance->lower ?instance->lower : (cur_state + 1));} else {next_target = THERMAL_NO_TARGET;}return next_target;}switch (trend) {case THERMAL_TREND_RAISING:------------------------------------升溫狀態下，next_target為cur_state+1，但是不超過instance->upper。if (throttle) {next_target = cur_state < instance->upper ?(cur_state + 1) : instance->upper;if (next_target < instance->lower)next_target = instance->lower;}break;case THERMAL_TREND_RAISE_FULL:if (throttle)next_target = instance->upper;break;case THERMAL_TREND_DROPPING:------------------------------------降溫狀態下，next_target為cur_state-1，但不低于instance->lower。存在特殊情況為THERMAL_NO_TARGET。if (cur_state <= instance->lower) {if (!throttle)next_target = THERMAL_NO_TARGET;} else {next_target = cur_state - 1;if (next_target > instance->upper)next_target = instance->upper;}break;case THERMAL_TREND_DROP_FULL:if (cur_state == instance->lower) {if (!throttle)next_target = THERMAL_NO_TARGET;} elsenext_target = instance->lower;break;default:--------------------------------------------------------stable狀態，不改變target值。break;}return next_target; }static void update_passive_instance(struct thermal_zone_device *tz,enum thermal_trip_type type, int value) {if (type == THERMAL_TRIP_PASSIVE || type == THERMAL_TRIPS_NONE)tz->passive += value;

Step Wise在中斷觸發后根據溫度的變化趨勢選擇Cooling狀態。而不是根據trip值選擇Cooling狀態。

* If the temperature is higher than a trip point,* a. if the trend is THERMAL_TREND_RAISING, use higher cooling* state for this trip point* b. if the trend is THERMAL_TREND_DROPPING, use lower cooling* state for this trip point* c. if the trend is THERMAL_TREND_RAISE_FULL, use upper limit* for this trip point* d. if the trend is THERMAL_TREND_DROP_FULL, use lower limit* for this trip point* If the temperature is lower than a trip point,* a. if the trend is THERMAL_TREND_RAISING, do nothing* b. if the trend is THERMAL_TREND_DROPPING, use lower cooling* state for this trip point, if the cooling state already* equals lower limit, deactivate the thermal instance* c. if the trend is THERMAL_TREND_RAISE_FULL, do nothing* d. if the trend is THERMAL_TREND_DROP_FULL, use lower limit,* if the cooling state already equals lower limit,* deactivate the thermal instanc

如上是step_wise.c中關于Step Wise governor的溫控策略。分別對高于或低于trip溫度下不同趨勢行為做出了解釋。

3.2 Fair Share分析

FairShare引入了weight概念。如果一個thermal zone中存在多個Cooling設備，不同的設備降溫效果可能不同，用weight表示降溫的能力。

weight大的設備得分較高，因此可以選擇更深的Cooling狀態。

static struct thermal_governor thermal_gov_fair_share = {.name = "fair_share",.throttle = fair_share_throttle, };int thermal_gov_fair_share_register(void) {return thermal_register_governor(&thermal_gov_fair_share); }void thermal_gov_fair_share_unregister(void) {thermal_unregister_governor(&thermal_gov_fair_share);

fair_share_throttle()首先根據溫度得出當前trip等級，然后綜合不同Cooling的weight等計算出每個Cooling設備的target。

static int fair_share_throttle(struct thermal_zone_device *tz, int trip) {struct thermal_instance *instance;int total_weight = 0;int total_instance = 0;int cur_trip_level = get_trip_level(tz);------------------------------------根據溫度獲取對應trip等級。list_for_each_entry(instance, &tz->thermal_instances, tz_node) {if (instance->trip != trip)continue;total_weight += instance->weight;total_instance++;}list_for_each_entry(instance, &tz->thermal_instances, tz_node) {int percentage;struct thermal_cooling_device *cdev = instance->cdev;if (instance->trip != trip)continue;if (!total_weight)percentage = 100 / total_instance;----------------------------------在都沒有定義weight的情況下，每個Cooling設備同樣percentage。elsepercentage = (instance->weight * 100) / total_weight;---------------如果存在weight的情況下，根據權重來劃分percentage。instance->target = get_target_state(tz, cdev, percentage,cur_trip_level);------------------------------------獲取當前Cooling設備對應的state。mutex_lock(&instance->cdev->lock);instance->cdev->updated = false;mutex_unlock(&instance->cdev->lock);thermal_cdev_update(cdev);}return 0; }static int get_trip_level(struct thermal_zone_device *tz) {int count = 0;int trip_temp;enum thermal_trip_type trip_type;if (tz->trips == 0 || !tz->ops->get_trip_temp)return 0;for (count = 0; count < tz->trips; count++) {tz->ops->get_trip_temp(tz, count, &trip_temp);if (tz->temperature < trip_temp)----------------------------------------根據thermal zone的溫度值，選擇合適的trip等級。break;}if (count > 0) {tz->ops->get_trip_type(tz, count - 1, &trip_type);----------------------僅是更新thermal trace point。trace_thermal_zone_trip(tz, count - 1, trip_type);} return count; }static long get_target_state(struct thermal_zone_device *tz,struct thermal_cooling_device *cdev, int percentage, int level) {unsigned long max_state;cdev->ops->get_max_state(cdev, &max_state); return (long)(percentage * level * max_state) / (100 * tz->trips);--------------

在weight為0的情況下，不同Cooling設備state均等映射到trip。在只有一個Cooling設備情況下，如果Cooling最大狀態和ThermalZone trip最大值相等，怎可以trip和狀態一一對應。

* Parameters used for Throttling:* P1. max_state: Maximum throttle state exposed by the cooling device.* P2. percentage[i]/100:* How 'effective' the 'i'th device is, in cooling the given zone.* P3. cur_trip_level/max_no_of_trips:* This describes the extent to which the devices should be throttled.* We do not want to throttle too much when we trip a lower temperature,* whereas the throttling is at full swing if we trip critical levels.* (Heavily assumes the trip points are in ascending order)* new_state of cooling device = P3 * P2 * P

fair_share.c中給出了計算Cooling設備狀態的計算公式，new_state=percentage*cur_trip_level*max_state/(100*max_no_of_trips)。

4. Thermal Cooling實例

創建一個Dummy Cooling驅動表示Cooling設備，通過thermal_cooling_device_register()注冊Thermal Cooling設備，將其和Thermal Zone綁定。在Thermal Zone中斷出發后，通過Governor選擇state，然后通過set_cur_state()執行溫控操作。

/* bind to generic thermal layer as cooling device*/ static struct thermal_cooling_device_ops dummy_cooling_ops = {.get_max_state = dummy_cooling_get_max_state,---------------------------Cooling設備最深降溫狀態。.get_cur_state = dummy_cooling_get_cur_state,---------------------------當前Cooling狀態。.set_cur_state = dummy_cooling_set_cur_state,---------------------------根據狀態，執行溫控操作。 };static int __init dummy_cooling_init(void) {int retval;dummy_cooling_dev = thermal_cooling_device_register("dummy_cooling", NULL,&dummy_cooling_ops);if (IS_ERR(dummy_cooling_dev)) {retval = -ENODEV;}return retval; } module_init(dummy_cooling_init);static void __exit dummy_cooling_exit(void) {thermal_cooling_device_unregister(dummy_cooling_dev); } module_exit(dummy_cooling_exit)

5. Thermal調試以及流程分析

首先使能已有Thermal調試手段，并添加proc節點模擬中斷觸發；然后基于log分析Thermal流程。

5.1 Thermal調試手段

對Termal的調試可以有兩種方式：

在thermal_core.c和step_wise.c的include之前#define DEBUG打開調試功能。
打開thermal trace point：echo 1 > /sys/kernel/debug/tracing/events/thermal/enable

為了模擬溫度變化，添加proc節點，然后使用腳本模擬溫度觸發流程。

#ifdef DP1000_THERMAL_STUB static int dp1000_temp_stub = 0; struct thermal_zone_device *thermal_zone_0, *thermal_zone_1; struct proc_dir_entry *dp1000_temp_proc = NULL; #endifstatic int dp1000_thermal_get_temp(struct thermal_zone_device *zone, int *temp) { #ifdef DP1000_THERMAL_STUB*temp = dp1000_temp_stub;--------------------------------------------------------替代從寄存器獲取溫度流程，使用/proc/dp1000_temp_stub輸入的溫度值。 #else ... #endifreturn 0; }#ifdef DP1000_THERMAL_STUB static int dp1000_temp_stub_proc_show(struct seq_file *m, void *v) {seq_printf(m, "%d\n", dp1000_temp_stub);return 0; }static int dp1000_temp_stub_proc_open(struct inode *inode, struct file *file) {return single_open(file, dp1000_temp_stub_proc_show, NULL); }static ssize_t dp1000_temp_stub_proc_write(struct file *file,const char __user *buffer, size_t count, loff_t *ppos) {int rc;rc = kstrtoint_from_user(buffer, count, 0, &dp1000_temp_stub);if (rc)return rc;thermal_zone_device_update(thermal_zone_0, THERMAL_EVENT_UNSPECIFIED);------------對/proc/dp1000_temp_stub寫入溫度，觸發流程。模擬中斷觸發流程。 // thermal_zone_device_update(thermal_zone_1, THERMAL_EVENT_UNSPECIFIED);return count; }static const struct file_operations dp1000_temp_stub_proc_fops = {.open = dp1000_temp_stub_proc_open,.read = seq_read,.llseek = seq_lseek,.release = single_release,.write = dp1000_temp_stub_proc_write, }; #endifstatic void dp1000_init_thermal(struct dp1000_thermal_priv *priv) { ...#ifdef DP1000_THERMAL_STUBif(!dp1000_temp_proc)dp1000_temp_proc = proc_create("dp1000_temp_stub", 0, NULL, &dp1000_temp_stub_proc_fops);------------創建/proc/dp1000_temp_stub節點。#endif ... }static int dp1000_thermal_probe(struct platform_device *pdev) { ...priv->zone = thermal_zone_device_register("dp1000_thermal", DP1000_THERMAL_TRIPS, 0,priv, &dp1000_thermal_zone_ops, NULL, 0, 0);#ifdef DP1000_THERMAL_STUBif(priv->zone->id == 0)thermal_zone_0 = priv->zone;else if(priv->zone->id == 1)thermal_zone_1 = priv->zone;#endif ...

5.2 Thermal流程分析

使用如下腳本進行Thermal流程調試：

echo 0 > /sys/kernel/debug/tracing/events/enable echo 1 > /sys/kernel/debug/tracing/events/thermal/enable echo > /sys/kernel/debug/tracing/tracefor i in 89 95 100 95 90 95 100 doecho -e "\n"echo $i > /proc/dp1000_temp_stubsleep 1 donecat /sys/kernel/debug/tracing/trac

得到的結果如下：

[ 35.900013] thermal thermal_zone0: last_temperature=0, current_temperature=89 [ 35.907277] thermal thermal_zone0: Trip0[type=0,temp=89]:trend=1,throttle=1--------------89度達到trip0的觸發溫度，而且是升溫狀態。trip1和trip2都沒有throttle。 [ 35.914290] thermal cooling_device0: cur_state=0 [ 35.918933] thermal cooling_device0: old_target=-1, target=1 [ 35.924619] thermal cooling_device0: zone0->target=1 [ 35.929608] thermal cooling_device0: zone1->target=4294967295 [ 35.935383] thermal cooling_device0: set to state 1--------------------------------------Cooling設備當前狀態時0，所以要將狀態設置為1。 [ 35.940293] thermal thermal_zone0: Trip1[type=0,temp=94]:trend=1,throttle=0 [ 35.947286] thermal thermal_zone0: Trip2[type=0,temp=99]:trend=1,throttle=0[ 36.999977] thermal thermal_zone0: last_temperature=89, current_temperature=95 [ 37.007326] thermal thermal_zone0: Trip0[type=0,temp=89]:trend=1,throttle=1 [ 37.014332] thermal cooling_device0: cur_state=1 [ 37.018973] thermal cooling_device0: old_target=1, target=2 [ 37.024570] thermal cooling_device0: zone0->target=2 [ 37.029558] thermal cooling_device0: zone1->target=4294967295 [ 37.035336] thermal cooling_device0: set to state 2--------------------------------------95度是trip1的觸發溫度，所以Cooling狀態從當前的1設置到2。trip2沒有throttle。 [ 37.040248] thermal thermal_zone0: Trip1[type=0,temp=94]:trend=1,throttle=1 [ 37.047240] thermal thermal_zone0: Trip2[type=0,temp=99]:trend=1,throttle=0 ..

從thermal trace可以才看出，首先獲取溫度，然后選擇trip，最后設置Cooling設備。

# TASK-PID CPU# |||| TIMESTAMP FUNCTION # | | | |||| | |sh-156 [000] .... 35.899971: thermal_temperature: thermal_zone=dp1000_thermal id=0 temp_prev=0 temp=89sh-156 [000] .... 35.907265: thermal_zone_trip: thermal_zone=dp1000_thermal id=0 trip=0 trip_type=ACTIVEsh-156 [000] .n.. 35.935374: cdev_update: type=dummy_cooling target=1sh-156 [000] .... 36.999933: thermal_temperature: thermal_zone=dp1000_thermal id=0 temp_prev=89 temp=95sh-156 [000] .n.. 37.007312: thermal_zone_trip: thermal_zone=dp1000_thermal id=0 trip=0 trip_type=ACTIVEsh-156 [000] .n.. 37.035327: cdev_update: type=dummy_cooling target=2sh-156 [000] .n.. 37.040238: thermal_zone_trip: thermal_zone=dp1000_thermal id=0 trip=1 trip_type=ACTIVEsh-156 [000] .... 38.079912: thermal_temperature: thermal_zone=dp1000_thermal id=0 temp_prev=95 temp=100sh-156 [000] .n.. 38.087374: thermal_zone_trip: thermal_zone=dp1000_thermal id=0 trip=0 trip_type=ACTIVEsh-156 [000] .n.. 38.115385: cdev_update: type=dummy_cooling target=3 ..

6. 小結

Thermal Framework一共可以分為四部分，Thermal Core、Thermal Zone、Thermal Governor、Thermal Cooling。

其中Core很穩定，主要是會使用；Governor也比較穩定，已有的Governor能覆蓋大部分場景；需要開發的主要有Thermal Zone的Driver和降溫設備Cooling。

在開發過程中，可以借助Trace point等措施進行問題定位。

聯系方式:arnoldlu@qq.com

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