【policy】【driver】【governor】

之前看过interactive调度器，对应的还有ondemand、performance等调度器，调度器是上层策略，而调度器的实现则是通过policy来实现的。

policy

Governor是调频的上层策略, policy是一次调频操作的实体 (句柄), 一个policy可以与多个cpu对应.

struct cpufreq_policy {/* CPUs sharing clock, require sw coordination(协调) */cpumask_var_t        cpus;   /* Online CPUs only */cpumask_var_t     related_cpus; /* Online + Offline CPUs */cpumask_var_t     real_cpus; /* Related and present */unsigned int        shared_type; /* ACPI: ANY or ALL affected CPUsshould set cpufreq *///  policy的managed cpu号. 一般为注册policy的cpu; 当该cpu offline时, // 会选取cpus的下一cpu作为新的managed cpu. 此时前面的cpu称为last_cpu.unsigned int       cpu;    /* cpu managing this policy, must be online */struct clk        *clk;// 硬件特性struct cpufreq_cpuinfo  cpuinfo;/* see above */// 软件特性unsigned int      min;    /* in kHz */unsigned int        max;    /* in kHz */unsigned int        cur;    /* in kHz, only needed if cpufreq* governors are used */// 类似变频之前的freq和目标frequnsigned int       restore_freq; /* = policy->cur before transition */unsigned int     target_freq; /* freq that the policy wants to set */unsigned int        suspend_freq; /* freq to set during suspend */unsigned int      policy; /* see above */unsigned int     last_policy; /* policy before unplug(拔核) */// 当前使用的governor，governor_data是tuables，governor_enabled是witch开关struct cpufreq_governor *governor; /* see below */void          *governor_data;bool         governor_enabled; /* governor start/stop flag */// 因为governor是可以切换的char         last_governor[CPUFREQ_NAME_LEN]; /* last governor used */struct work_struct update; /* if update_policy() needs to be* called, but you're in IRQ context */// user_policy一般用于保存原始参数，因为温度过高的时候最大频率可能会发生变化struct cpufreq_user_policy user_policy;struct cpufreq_frequency_table   *freq_table;struct list_head        policy_list;struct kobject      kobj;struct completion  kobj_unregister;struct notifier_block pm_qos_freq_nb;/** The rules for this semaphore:* - Any routine that wants to read from the policy structure will*   do a down_read on this semaphore.* - Any routine that will write to the policy structure and/or may take away*   the policy altogether (eg. CPU hotplug), will hold this lock in write*   mode before doing so.** Additional rules:* - Lock should not be held across*     __cpufreq_governor(data, CPUFREQ_GOV_POLICY_EXIT);*/struct rw_semaphore   rwsem;（信号量）/** Fast switch flags:* - fast_switch_possible should be set by the driver if it can*   guarantee that frequency can be changed on any CPU sharing the*   policy and that the change will affect all of the policy CPUs then.* - fast_switch_enabled is to be set by governors that support fast*   freqnency switching with the help of cpufreq_enable_fast_switch().*/bool                    fast_switch_possible;bool                    fast_switch_enabled;/** Preferred average time interval between consecutive invocations of* the driver to set the frequency for this policy.  To be set by the* scaling driver (0, which is the default, means no preference).*/unsigned int      up_transition_delay_us;unsigned int     down_transition_delay_us;/* Cached frequency lookup from cpufreq_driver_resolve_freq. */unsigned int cached_target_freq;int cached_resolved_idx;/* Synchronization for frequency transitions */bool         transition_ongoing; /* Tracks transition status */spinlock_t        transition_lock;wait_queue_head_t   transition_wait;struct task_struct  *transition_task; /* Task which is doing the transition *//* cpufreq-stats */// 对应的是stat这个节点struct cpufreq_stats    *stats;/* For cpufreq driver's internal use */void         *driver_data;
};

其中

struct cpufreq_cpuinfo {// 硬件特性unsigned int      max_freq;unsigned int       min_freq;/* in 10^(-9) s = nanoseconds */纳秒为单位unsigned int     transition_latency;
};

struct cpufreq_user_policy {unsigned int     min;    /* in kHz */unsigned int        max;    /* in kHz */
};

不管具体的驱动如何变化，核心层都提供了节点，而不是每家驱动各自添加的，这就解释了为什么不同芯片厂商，只要架构是相同的，他们的节点就都相同

/*** show_cpuinfo_cur_freq - current CPU frequency as detected by hardware*/
static ssize_t show_cpuinfo_cur_freq(struct cpufreq_policy *policy,char *buf)
{unsigned int cur_freq = __cpufreq_get(policy);if (cur_freq)return sprintf(buf, "%u\n", cur_freq);return sprintf(buf, "<unknown>\n");
}
/*** show_scaling_driver - show the cpufreq driver currently loaded*/
static ssize_t show_scaling_driver(struct cpufreq_policy *policy, char *buf)
{return scnprintf(buf, CPUFREQ_NAME_PLEN, "%s\n", cpufreq_driver->name);
}
/*** show_scaling_governor - show the current policy for the specified CPU*/static ssize_t show_scaling_governor(struct cpufreq_policy *policy, char *buf)
{// 也就是说policy里面的powersave和performance，和governor里面的是不一样的嘛！if (policy->policy == CPUFREQ_POLICY_POWERSAVE)return sprintf(buf, "powersave\n");else if (policy->policy == CPUFREQ_POLICY_PERFORMANCE)return sprintf(buf, "performance\n");else if (policy->governor)return scnprintf(buf, CPUFREQ_NAME_PLEN, "%s\n", policy->governor->name);return -EINVAL;
}
static ssize_t show_scaling_cur_freq(struct cpufreq_policy *policy, char *buf)
{ssize_t ret;if (cpufreq_driver && cpufreq_driver->setpolicy && cpufreq_driver->get)ret = sprintf(buf, "%u\n", cpufreq_driver->get(policy->cpu));elseret = sprintf(buf, "%u\n", policy->cur);return ret;
}
static ssize_t show_scaling_cur_freq(struct cpufreq_policy *policy, char *buf)
{ssize_t ret;// 一般都是没有设置setpolicy函数的if (cpufreq_driver && cpufreq_driver->setpolicy && cpufreq_driver->get)ret = sprintf(buf, "%u\n", cpufreq_driver->get(policy->cpu));elseret = sprintf(buf, "%u\n", policy->cur);return ret;
}

driver

struct cpufreq_driver {char      name[CPUFREQ_NAME_LEN];u8       flags;void      *driver_data;/* needed by all drivers */int     (*init)(struct cpufreq_policy *policy);int      (*verify)(struct cpufreq_policy *policy);//检查policy的参数是否被支持// 定义下面两个中的一个/* define one out of two *///如果不支持通过governor选择合适的运行频率，则实现setpolicy回调函数，//这样系统只能支持CPUFREQ_POLICY_POWERSAVE和CPUFREQ_POLICY_PERFORMANCE这两种工作策略 int       (*setpolicy)(struct cpufreq_policy *policy);/** On failure, should always restore frequency to policy->restore_freq* (i.e. old freq).*///实现target回调函数，通过target回调设定governor所需要的频率//target或者target_index设定目标频率int       (*target)(struct cpufreq_policy *policy,unsigned int target_freq,unsigned int relation);    /* Deprecated */int     (*target_index)(struct cpufreq_policy *policy,unsigned int index);/** Only for drivers with target_index() and CPUFREQ_ASYNC_NOTIFICATION* unset.** get_intermediate should return a stable intermediate frequency* platform wants to switch to and target_intermediate() should set CPU* to to that frequency, before jumping to the frequency corresponding* to 'index'. Core will take care of sending notifications and driver* doesn't have to handle them in target_intermediate() or* target_index().** Drivers can return '0' from get_intermediate() in case they don't* wish to switch to intermediate frequency for some target frequency.* In that case core will directly call ->target_index().*/unsigned int    (*get_intermediate)(struct cpufreq_policy *policy,unsigned int index);int       (*target_intermediate)(struct cpufreq_policy *policy,unsigned int index);/* should be defined, if possible */// 从硬件获取当前frequnsigned int (*get)(unsigned int cpu);/* optional */int      (*bios_limit)(int cpu, unsigned int *limit);// 与init对应int       (*exit)(struct cpufreq_policy *policy);void     (*stop_cpu)(struct cpufreq_policy *policy);// 针对boot cpu, 因为其他cpu已经在suspend前offline了int     (*suspend)(struct cpufreq_policy *policy);int       (*resume)(struct cpufreq_policy *policy);/* Will be called after the driver is fully initialized */void     (*ready)(struct cpufreq_policy *policy);struct freq_attr **attr;/* platform specific boost support code */bool      boost_supported;bool        boost_enabled;int       (*set_boost)(int state);
};

governor

struct cpufreq_governor {char    name[CPUFREQ_NAME_LEN];int  initialized;//指向一个回调函数，CPUFreq Core会在不同的阶段调用该回调函数，用于该governor的启动、停止、初始化、退出动作int   (*governor) (struct cpufreq_policy *policy,unsigned int event);ssize_t  (*show_setspeed)    (struct cpufreq_policy *policy,char *buf);int   (*store_setspeed)   (struct cpufreq_policy *policy,unsigned int freq);unsigned int max_transition_latency; /* HW must be able to switch tonext freq faster than this value in nano secs or wewill fallback to performance governor *///所有注册的governor都会利用该字段链接在一个全局链表中，以供系统查询和使用struct list_head  governor_list;struct module     *owner;
};

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【policy】【driver】【governor】

policy

不管具体的驱动如何变化，核心层都提供了节点，而不是每家驱动各自添加的，这就解释了为什么不同芯片厂商，只要架构是相同的，他们的节点就都相同

driver

governor

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