Linux Thermal Framework分析及实施
关键词：Zone、Cooling、Governor、Step Wise、Fair Share、trip等等。
Linux Thermal的目的是控制系统运行过程中采样点温度，避免温度过高造成器件损坏，确保芯片长期稳定工作。
整个Thermal框架可以分为四部分：
- Thermal Driver负责将获取温度设备，注册成struct thermal_zone_device，比如Temp Sensor、NTC等。
- Thermal Governor则负责如何控制温度，注册成struct thermal_governor，比如Step Wise、Bang Bang等等。
- Thermal Cooling负责将控制温度设备，注册成struct thermal_cooling_device，比如风扇、CPU、DDR、GPU等。
- Thermal Core则是Thermal Driver、Thermal Governor、Thermal Governor的粘合剂，同时提供了用户空间sysfs节点等通用功能。
所以Thermal的工作流程是通过Thermal Driver获取温度，然后经过Thermal Governor决策，最后通过Thermal Cooling执行温度控制。
下面首先从总体详细分析Thermal框架以及数据结构、API(1. Thermal框架分析)，然后分别分析Thermal Driver实例(2. Thermal Driver实例)、Thermal Governor(Step Wise和Fair Share)(3. Thermal Governor分析)、以及Thermal Cooling实例(4. Thermal Cooling实例)。
最后将这些内容串起来，分析Thermal是如何控制温度的。
1. Thermal框架分析
1.1 Thermal数据结构
struct thermal_zone_device是对获取温度设备的抽象，成员ops是对该Thermal Zone操作的抽象；governor是该Thermal Zone所使用的调温策略；thermal_instances是该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数目。 unsigned long trips_disabled; /* bitmap for disabled trips */ int passive_delay; int polling_delay;-------------------------------------------------轮询读取温度的建个，0表示采用中断形式。 int temperature;---------------------------------------------------当前温度。 int last_temperature;----------------------------------------------最近一次温度。 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;------------------------------当前thermal zone操作函数集。 struct thermal_zone_params *tzp;----------------------------------当前thermal zone参数。 struct thermal_governor *governor; void *governor_data; struct list_head thermal_instances;-------------------------------当前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 *);------------------------将cooling device绑定到thermal zone中，两者通过struct thermal_instances在thermal_zone_bind_cooling_device()中绑定。 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是对降温设备的抽象，对风扇设备就是不同的转速，对CPU、DDR、GPU就是不同的电压或者频率。
struct thermal_cooling_device_ops是Cooling Device操作函数集，其中set_cur_state()是对设备进行温度控制。
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是对温控策略的抽象，也就是根据Thermal Zone的trip来选择Thermal Cooling设备的行为。比如，温度越高风扇转速越快；温度越高CPU运行在更低电压和频率上。
struct thermal_governor { char name[THERMAL_NAME_LENGTH]; int (*bind_to_tz)(struct thermal_zone_device *tz);---------------------将一个governor绑定到thermal zone得一个trip上。 void (*unbind_from_tz)(struct thermal_zone_device *tz);----------------将一个governor从thermal zone解绑。 int (*throttle)(struct thermal_zone_device *tz, int trip);-------------根据trip遍历当前thermal zone下所有的cooling device执行温控策略。 struct list_head governor_list;-------------------------------------thermal_governor_list上的一个列表元素。 };
所有的策略选择都是通过throttle()函数进行的，不同的Governor的区别也主要在这里。内核已经实现了Step Wise、User等等，并且还在演进中。
通过struct thermal_instances可以将thermal zone和thermal cooling设备绑定起来。
struct thermal_instance { int id; char name[THERMAL_NAME_LENGTH]; struct thermal_zone_device *tz;-------------------------------------------绑定的thermal zone。 struct thermal_cooling_device *cdev;--------------------------------------绑定的thermal cooling设备。 int trip;-----------------------------------------------------------------对应的thermal zone的trip。 bool initialized; unsigned long upper; /* Highest cooling state for this trip point */---cooling设备的最高降温状态。 unsigned long lower; /* Lowest cooling state for this trip point */----cooling设备最低降温状态。 unsigned long target; /* expected cooling state */---------------------cooling设备的当前状态，也是thermal_cooling_device_ops->set_cur_state()设置后的值。 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上的节点。 struct list_head cdev_node; /* node in cdev->thermal_instances */---------thermal_cooling_device->thermal_instances上的节点。 unsigned int weight; /* The weight of the cooling device */ };
thermal_device_mode表示当前的thermal zone是否使能。
thermal_trip_type表示thermal zone的当前trip类型，其中ACTIVE和PASSIVE属于non-critical类型，交由Governor进行处理；HOT和CRITICAL属于critical类型，其中CRITICAL会执行orderly_poweroff()。
thermal_trend表示thermal zone的温度趋势，是平缓、上升、下降还是跳跃式的，这就给Governor选择trip提供依据。
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 */-----------------------表示温度平稳。 THERMAL_TREND_RAISING, /* temperature is raising */---------------------表示当前温度趋势是升高的。 THERMAL_TREND_DROPPING, /* temperature is dropping */-------------------表示当前温度趋势是降低的。 THERMAL_TREND_RAISE_FULL, /* apply highest cooling action */------------直接应用upper对应的trip。 THERMAL_TREND_DROP_FULL, /* apply lowest cooling action */--------------直接应用lower对应的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的粘合剂。
通过Thermal core提供的API，将这三者相互关联起来；从Thermal Zone设备获取温度，选择对应的Thermal Governor，Thermal Governor设置Thermal Cooling的状态，进而达到控制温度的目的。
通过thermal_zone_device_register()注册thermal zone设备，创建一系列sysfs节点，并且和governor、cooling进行绑定。
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链表，放置struct thermal_instances实例。通过thermal_instances可以关联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;------------------------------------创建的设备会在/sys/class/thermal下面有个链接。 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);--------------------------------创建/sys/devices/virtual/thermal/thermal_zone*设备。 if (result) { release_idr(&thermal_tz_idr, &thermal_idr_lock, tz->id); kfree(tz); return ERR_PTR(result); } /* sys I/F */---------------------------------------------------------分别创建type、temp、mode、trip等sysfs节点。 if (type) { result = device_create_file(&tz->device, &dev_attr_type); if (result) goto unregister; } ... result = create_trip_attrs(tz, mask);-----------------------为每个trip创建trip_point_*_temp/hyst/type节点。 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则通过__find_governor()选定；否则使用默认def_governor。 governor = __find_governor(tz->tzp->governor_name); else governor = def_governor; result = thermal_set_governor(tz, governor);-----------------将governor绑定到tz上，优先使用bind_to_tz()执行绑定；否则直接指定tz->governor为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);------------------------将当前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);-------------------------------------------------------调用tz->ops->bind()将thermal_cdev_list上的cooling设备绑定到tz上。 INIT_DELAYED_WORK(&(tz->poll_queue), thermal_zone_device_check); thermal_zone_device_reset(tz);-------------------------------------对thermal zone的温度等复位。 /* 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);------------------------------先调用当前governor进行unbind()。 if (new_gov && new_gov->bind_to_tz) { ret = new_gov->bind_to_tz(tz);---------------------------------使用当前governor进行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) {-----------遍历thermal_cdev_list的cooling设备，然后和当前thermal zone进行绑定。 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, struct thermal_zone_device, poll_queue.work); thermal_zone_device_update(tz, THERMAL_EVENT_UNSPECIFIED); }
thermal_zone_device_unregister()则执行相反的操作，将thermal zone从thermal_tz_list上摘除，并且和cooling设备去绑定，以及删除一系列sysfs节点。
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()创建cooling设备并放入thermal_cdev_list中，以及相关sysfs节点，并将cooling设备和thermal zone绑定。
thermal_cooling_device_unregister()则进行相反的操作。
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设备同样会在/sys/class/thermal下创建链接。 cdev->device.groups = cooling_device_attr_groups;--------------------创建cur_state、max_state、type三个sysfs节点。 cdev->devdata = devdata; dev_set_name(&cdev->device, "cooling_device%d", cdev->id); result = device_register(&cdev->device);-----------------------------创建/sys/devices/virtual/thermal/cooling_device*设备节点。 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);---------------------------将设备放入thermal_cdev_list设备链表。 mutex_unlock(&thermal_list_lock); /* Update binding information for 'this' new cdev */ bind_cdev(cdev);-----------------------------------------------------遍历thermal_tz_list，将cdev绑定到上面的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()首先判断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()则相反，将governor和thermal zone调用unbind_from_tz()并置空；最后从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) {--------------------检查此governor是否已经在thermal_governor_list中，如果不在则加入thermal_governor_list。并且判断是否为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已经制定governor，则跳过。 continue; name = pos->tzp->governor_name; if (!strncasecmp(name, governor->name, THERMAL_NAME_LENGTH)) { int ret; ret = thermal_set_governor(pos, governor);----------------给当前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()通过创建thermal_instances设备将Thermal Zone和Thermal Cooling绑定，这样Thermal Zone就可以根据温度处理Thermal Cooling设备。
thermal_zone_unbind_cooling_device() 则将关联Thermal Zone和Thermal Cooling的thermal_instances从两者的链表上摘除。
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);----------------------从Cooling设备操作函数get_max_state()获取max_state，进而决定thermal_instances的lower和upper范围。 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连接到cooling_devicex。 if (result) goto release_idr; sprintf(dev->attr_name, "cdev%d_trip_point", dev->id);-----------------------创建cdevx_trip_point和cdevx_weight节点。 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驱动调用，有可能是polling或者中断触发。
然后更新当前Thermal Zone的温度，最后根据温度值通过handle_thermal_trip()进行处理。
monitor_thermal_zone()根据passive和polling的设置决定是否启动thermal_zone_device->pool_queue这个delayed_work。
整个polling流程由thermal_zone_device_update()触发，依次流程为：handle_thermal_trip()中启动monitor_thermal_zone()，monitor_thermal_zone()中调用mod_delayed_work()进行poll_queue延时值的更新。如果thermal zone有多个trip，poll_queue延时值可能被多次更新。poll_queue放入system_freezable_wq后，达到时间后调用thermal_zone_device_check()，进而调用thermal_zone_device_update()完成周期性循环。
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); else dev_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); else handle_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)-----------------------------------分别设置passive和polling两种延时工作。 thermal_zone_device_set_polling(tz, tz->passive_delay); else if (tz->polling_delay) thermal_zone_device_set_polling(tz, tz->polling_delay); else thermal_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)----------------------------------将poll_queue放入system_freezable_wq工作队列上，多次调用mod_delayed_work()在超时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)); else cancel_delayed_work(&tz->poll_queue);----------如果delay为0，则取消poll_queue延时工作。 }
thermal_cdev_update()是由Governor调用进行cooling device设置。
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) {----------遍历当前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;---------------------------------------------确保cooling设备选择最高cooling状态，然后调用cooling设备的set_cur_state()进行降温。 } 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()在内核fs_initcall()阶段调用，进行governor、thermal_class、Generic Netlink注册等操作。
static int __init thermal_init(void) { int result; result = thermal_register_governors();---------------注册平台支持的所有governor。 if (result) goto error; result = class_register(&thermal_class);-------------注册thermal_class。 if (result) goto unregister_governors; result = genetlink_init();---------------------------注册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实例
下面首先简单看一下Temp Sensor的硬件，然后分析DTS，最后分析驱动的实现。
2.1 Temp Sensor硬件
对Temp Sensor的配置可以通过APB BUS进行，包括两个Temp Sensor，每个Temp Sensor中包括3个Trip触发点设置，以及一个Alarm配置。
Trip达到后会触发中断，CPU的INTC收到中断后，进行中断处理；Alarm达到后直接导致CPU复位或者关闭PLL。
Temp Sensor默认使用32K时钟，每32768个时钟采样一次。还可以根据情况选择24M作为时钟输入。
一个重要工作就是根据实际情况，选定Trip温度以及Alarm温度。
另一个核心的工作就是确定如何根据Data寄存器的值计算出温度值。这就需要计算两个参数A和B。
通过其他测量手段读出温度值，以及当前温度值下的DBN<11:0>。这获取一系列数据之后，通过直线数据拟合，得出A和B的值。
2.2 Temp Sensor DTS
DTS是对硬件的抽象，包括寄存器配置地址和范围、中断、3个trip温度、一个alarm温度。
sensor0: sensor0@0xfc20a000 { compatible = "xxx,xxxxxx-thermal"; reg = <0xfc20a000 0x20>; interrupts = <38>; xxx,temp0 = <90>; xxx,temp1 = <95>; xxx,temp2 = <100>; xxx,alarm_temp = <120>; xxx,alarm_en; };
从DTS可以看出，通过配置不同trip和alarm的温度，中断触发后，CPU会读取温度进行相应处理。
2.3 Temp Sensor驱动
Temp Sensor的驱动首先解析DTS，并进行iomem映射；然后注册中断以及下半部workqueue处理；再进行硬件设置；最后注册thermal zone设备。
在设备正常工作中，根据配置的trip和alarm值触发中断，然后进行work处理；中间会用到struct thermal_zone_device_ops提供的成员函数获取温度、和cooling设备绑定等等操作。
2.3.1 Thermal Sensor注册
static int xxxxxx_thermal_probe(struct platform_device *pdev) { struct xxxxxx_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, "xxx,temp0", &priv->temp0) < 0) { dev_dbg(&pdev->dev, "\"temp0\" property is missing, using default value.\n"); priv->temp0 = 0; } ... INIT_DELAYED_WORK(&priv->work, xxxxxx_thermal_work);---------------------创建delayed_work，对应的处理函数是xxxxxx_thermal_work()。 priv->irq = platform_get_irq(pdev, 0); ... ret = devm_request_irq(&pdev->dev, priv->irq, xxxxxx_thermal_interrupt, 0, dev_name(&pdev->dev), priv);-------------------------------irq注册，中断处理函数为xxxxxx_thermal_interrupt()。 ... xxxxxx_init_thermal(priv);------------------------------------------------硬件初始化。 priv->zone = thermal_zone_device_register("xxxxxx_thermal", xxxxxx_THERMAL_TRIPS, 0, priv, &xxxxxx_thermal_zone_ops, NULL, 0, 0);-------Thermal Zone注册。 #ifdef xxxxxx_THERMAL_STUB if(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 xxxxxx_thermal_remove(struct platform_device *pdev) { struct xxxxxx_thermal_priv *priv = dev_get_drvdata(&pdev->dev); ... return 0; } static const struct of_device_id xxxxxx_thermal_id_table[] = { { .compatible = "xxx,xxxxxx-thermal" },-----------------------------------和dts匹配。 { } }; MODULE_DEVICE_TABLE(of, xxxxxx_thermal_id_table); static struct platform_driver xxxxxx_thermal_driver = { .probe = xxxxxx_thermal_probe, .remove = xxxxxx_thermal_remove, .driver = { .name = "xxxxxx_thermal", .of_match_table = xxxxxx_thermal_id_table, }, }; module_platform_driver(xxxxxx_thermal_driver);
xxxxxx_thermal_zone_ops函数集是Thermal Sensor的核心，对Thermal Zone的操作都是通过调用这些函数实现的。
static struct thermal_zone_device_ops xxxxxx_thermal_zone_ops = { .bind = xxxxxx_thermal_bind, .unbind = xxxxxx_thermal_unbind, .get_trip_type = xxxxxx_thermal_get_trip_type, .get_trip_hyst = xxxxxx_thermal_get_trip_hyst, .get_temp = xxxxxx_thermal_get_temp, .set_trip_temp = xxxxxx_thermal_set_trip_temp, .get_trip_temp = xxxxxx_thermal_get_trip_temp, .get_crit_temp = xxxxxx_thermal_get_crit_temp, };
2.3.2 Thermal Driver中断能触发流程
当Thermal Sensor的温度达到trip值时，会触发中断。
然后进入xxxxxx_thermal_interrupt()，在延时300ms进行xxxxxx_thermal_work()处理。
static irqreturn_t xxxxxx_thermal_interrupt(int irq, void *id) { struct xxxxxx_thermal_priv *priv = (struct xxxxxx_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 xxxxxx_thermal_work(struct work_struct *work) { struct xxxxxx_thermal_priv *priv; priv = container_of(work, struct xxxxxx_thermal_priv, work.work); thermal_zone_device_update(priv->zone, THERMAL_EVENT_UNSPECIFIED); }
最终的工作交给thermal_zone_device_update()进行，读取温度，根据温度选择trip。
3. Thermal Governor分析
下面简单分析两个Governor：Step Wise和Fair Share。
3.1 Step Wise分析
首先看一下Step Wise的注册。
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，首先选用当前thermal zone的throttle()进行处理。
对于Step Wise governor来说，对外的接口只有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);-----------------------------根据当前温度和上次温度对比，得到温度趋势；然后根据温度趋势得出Cooling设备对应的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);------------------------遍历cdev->thermal_instances选择最深的cooling状态。然后调用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);----------------------------------------根据当前温度tz->temperature和tz->last_temperature对比，判定tend是STABLE/RAISING/DROPPING等中的一种。 if (tz->temperature >= trip_temp) { throttle = true;---------------------------------------------------throttle为true表示需要节流，即降温。 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不做处理。 continue; old_target = instance->target; instance->target = get_target_state(instance, trend, throttle);----instance->target是将要设置到Cooling设备的状态。 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为false表示Cooling设备需要更新状态，在thermal_cdev_update()中会进行判断。 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:------------------------------------升温状态下，next_target为cur_state+1，但是不超过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:------------------------------------降温状态下，next_target为cur_state-1，但不低于instance->lower。存在特殊情况为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; } else next_target = instance->lower; break; default:--------------------------------------------------------stable状态，不改变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在中断触发后根据温度的变化趋势选择Cooling状态。而不是根据trip值选择Cooling状态。
* 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 instance
如上是step_wise.c中关于Step Wise governor的温控策略。分别对高于或低于trip温度下不同趋势行为做出了解释。
3.2 Fair Share分析
FairShare引入了weight概念。如果一个thermal zone中存在多个Cooling设备，不同的设备降温效果可能不同，用weight表示降温的能力。
weight大的设备得分较高，因此可以选择更深的Cooling状态。
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()首先根据温度得出当前trip等级，然后综合不同Cooling的weight等计算出每个Cooling设备的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);------------------------------------根据温度获取对应trip等级。 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;----------------------------------在都没有定义weight的情况下，每个Cooling设备同样percentage。 else percentage = (instance->weight * 100) / total_weight;---------------如果存在weight的情况下，根据权重来划分percentage。 instance->target = get_target_state(tz, cdev, percentage, cur_trip_level);------------------------------------获取当前Cooling设备对应的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)----------------------------------------根据thermal zone的温度值，选择合适的trip等级。 break; } if (count > 0) { tz->ops->get_trip_type(tz, count - 1, &trip_type);----------------------仅是更新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为0的情况下，不同Cooling设备state均等映射到trip。在只有一个Cooling设备情况下，如果Cooling最大状态和ThermalZone trip最大值相等，怎可以trip和状态一一对应。
* 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 * P1
fair_share.c中给出了计算Cooling设备状态的计算公式，new_state=percentage*cur_trip_level*max_state/(100*max_no_of_trips)。
4. Thermal Cooling实例
创建一个Dummy Cooling驱动表示Cooling设备，通过thermal_cooling_device_register()注册Thermal Cooling设备，将其和Thermal Zone绑定。在Thermal Zone中断出发后，通过Governor选择state，然后通过set_cur_state()执行温控操作。
/* 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设备最深降温状态。 .get_cur_state = dummy_cooling_get_cur_state,---------------------------当前Cooling状态。 .set_cur_state = dummy_cooling_set_cur_state,---------------------------根据状态，执行温控操作。 }; 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调试以及流程分析
首先使能已有Thermal调试手段，并添加proc节点模拟中断触发；然后基于log分析Thermal流程。
5.1 Thermal调试手段
对Termal的调试可以有两种方式：
- 在thermal_core.c和step_wise.c的include之前#define DEBUG打开调试功能。
- 打开thermal trace point：echo 1 > /sys/kernel/debug/tracing/events/thermal/enable
为了模拟温度变化，添加proc节点，然后使用脚本模拟温度触发流程。
#ifdef xxxxxx_THERMAL_STUB static int xxxxxx_temp_stub = 0; struct thermal_zone_device *thermal_zone_0, *thermal_zone_1; struct proc_dir_entry *xxxxxx_temp_proc = NULL; #endif static int xxxxxx_thermal_get_temp(struct thermal_zone_device *zone, int *temp) { #ifdef xxxxxx_THERMAL_STUB *temp = xxxxxx_temp_stub;--------------------------------------------------------替代从寄存器获取温度流程，使用/proc/xxxxxx_temp_stub输入的温度值。 #else ... #endif return 0; } #ifdef xxxxxx_THERMAL_STUB static int xxxxxx_temp_stub_proc_show(struct seq_file *m, void *v) { seq_printf(m, "%d\n", xxxxxx_temp_stub); return 0; } static int xxxxxx_temp_stub_proc_open(struct inode *inode, struct file *file) { return single_open(file, xxxxxx_temp_stub_proc_show, NULL); } static ssize_t xxxxxx_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, &xxxxxx_temp_stub); if (rc) return rc; thermal_zone_device_update(thermal_zone_0, THERMAL_EVENT_UNSPECIFIED);------------对/proc/xxxxxx_temp_stub写入温度，触发流程。模拟中断触发流程。 // thermal_zone_device_update(thermal_zone_1, THERMAL_EVENT_UNSPECIFIED); return count; } static const struct file_operations xxxxxx_temp_stub_proc_fops = { .open = xxxxxx_temp_stub_proc_open, .read = seq_read, .llseek = seq_lseek, .release = single_release, .write = xxxxxx_temp_stub_proc_write, }; #endif static void xxxxxx_init_thermal(struct xxxxxx_thermal_priv *priv) { ... #ifdef xxxxxx_THERMAL_STUB if(!xxxxxx_temp_proc) xxxxxx_temp_proc = proc_create("xxxxxx_temp_stub", 0, NULL, &xxxxxx_temp_stub_proc_fops);------------创建/proc/xxxxxx_temp_stub节点。 #endif ... } static int xxxxxx_thermal_probe(struct platform_device *pdev) { ... priv->zone = thermal_zone_device_register("xxxxxx_thermal", xxxxxx_THERMAL_TRIPS, 0, priv, &xxxxxx_thermal_zone_ops, NULL, 0, 0); #ifdef xxxxxx_THERMAL_STUB if(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
使用如下脚本进行Thermal流程调试：
echo 0 > /sys/kernel/debug/tracing/events/enable echo 1 > /sys/kernel/debug/tracing/events/thermal/enable echo > /sys/kernel/debug/tracing/trace for i in 89 95 100 95 90 95 100 do echo -e "\n" echo $i > /proc/xxxxxx_temp_stub sleep 1 done cat /sys/kernel/debug/tracing/trace
得到的结果如下：
[ 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度达到trip0的触发温度，而且是升温状态。trip1和trip2都没有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设备当前状态时0，所以要将状态设置为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的触发温度，所以Cooling状态从当前的1设置到2。trip2没有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
...
从thermal trace可以才看出，首先获取温度，然后选择trip，最后设置Cooling设备。
# TASK-PID CPU# |||| TIMESTAMP FUNCTION # | | | |||| | | sh-156 [000] .... 35.899971: thermal_temperature: thermal_zone=xxxxxx_thermal id=0 temp_prev=0 temp=89 sh-156 [000] .... 35.907265: thermal_zone_trip: thermal_zone=xxxxxx_thermal id=0 trip=0 trip_type=ACTIVE sh-156 [000] .n.. 35.935374: cdev_update: type=dummy_cooling target=1 sh-156 [000] .... 36.999933: thermal_temperature: thermal_zone=xxxxxx_thermal id=0 temp_prev=89 temp=95 sh-156 [000] .n.. 37.007312: thermal_zone_trip: thermal_zone=xxxxxx_thermal id=0 trip=0 trip_type=ACTIVE sh-156 [000] .n.. 37.035327: cdev_update: type=dummy_cooling target=2 sh-156 [000] .n.. 37.040238: thermal_zone_trip: thermal_zone=xxxxxx_thermal id=0 trip=1 trip_type=ACTIVE sh-156 [000] .... 38.079912: thermal_temperature: thermal_zone=xxxxxx_thermal id=0 temp_prev=95 temp=100 sh-156 [000] .n.. 38.087374: thermal_zone_trip: thermal_zone=xxxxxx_thermal id=0 trip=0 trip_type=ACTIVE sh-156 [000] .n.. 38.115385: cdev_update: type=dummy_cooling target=3 ...
6. 小结
Thermal Framework一共可以分为四部分，Thermal Core、Thermal Zone、Thermal Governor、Thermal Cooling。
其中Core很稳定，主要是会使用；Governor也比较稳定，已有的Governor能覆盖大部分场景；需要开发的主要有Thermal Zone的Driver和降温设备Cooling。
在开发过程中，可以借助Trace point等措施进行问题定位。
联系方式:arnoldlu@qq.com
