userspace governer 是用户空间设定cpu freq频率来运行，因此提供了show_setspeed和store_setspeed 两个函数用于现实当前的cpu freq 和设置当前cpu freq
125 static struct cpufreq_governor cpufreq_gov_userspace = {
126 .name = "userspace",
127 .governor = cpufreq_governor_userspace,
128 .store_setspeed = cpufreq_set,
129 .show_setspeed = show_speed,
130 .owner = THIS_MODULE,
131 };
我们看看store_setspeed的实现cpufreq_set。
就是把freq通过__cpufreq_driver_target设定到寄存器中
32 static int cpufreq_set(struct cpufreq_policy *policy, unsigned int freq)
33 {
34 int ret = -EINVAL;
35 unsigned int *setspeed = policy->governor_data;
36
37 pr_debug("cpufreq_set for cpu %u, freq %u kHz\n", policy->cpu, freq);
38
39 mutex_lock(&userspace_mutex);
40 if (!per_cpu(cpu_is_managed, policy->cpu))
41 goto err;
42
43 *setspeed = freq;
44
45 ret = __cpufreq_driver_target(policy, freq, CPUFREQ_RELATION_L);
46 err:
47 mutex_unlock(&userspace_mutex);
48 return ret;
49 }
而show_setspeed的实现show_speed就是显示当前的freq.
51 static ssize_t show_speed(struct cpufreq_policy *policy, char *buf)
52 {
53 return sprintf(buf, "%u\n", policy->cur);
54 }
需要注意的是set 和show的freq有可能不同.
我们再来看看governor的实现函数cpufreq_governor_userspace
主要处理CPUFREQ_GOV_POLICY_INIT/CPUFREQ_GOV_START event 。
其中CPUFREQ_GOV_START只是将percpu中的当前cpu 置1表示当前cpu已经设定过freq。并保存这个频率.
static int cpufreq_governor_userspace(struct cpufreq_policy *policy,
69 unsigned int event)
70 {
71 unsigned int *setspeed = policy->governor_data;
72 unsigned int cpu = policy->cpu;
73 int rc = 0;
74
75 if (event == CPUFREQ_GOV_POLICY_INIT)
76 return cpufreq_userspace_policy_init(policy);
77
78 if (!setspeed)
79 return -EINVAL;
80
81 switch (event) {
82 case CPUFREQ_GOV_POLICY_EXIT:
83 mutex_lock(&userspace_mutex);
84 policy->governor_data = NULL;
85 kfree(setspeed);
86 mutex_unlock(&userspace_mutex);
87 break;
88 case CPUFREQ_GOV_START:
89 BUG_ON(!policy->cur);
90 pr_debug("started managing cpu %u\n", cpu);
91
92 mutex_lock(&userspace_mutex);
93 per_cpu(cpu_is_managed, cpu) = 1;
94 *setspeed = policy->cur;
95 mutex_unlock(&userspace_mutex);
96 break;
97 case CPUFREQ_GOV_STOP:
98 pr_debug("managing cpu %u stopped\n", cpu);
99
100 mutex_lock(&userspace_mutex);
101 per_cpu(cpu_is_managed, cpu) = 0;
102 *setspeed = 0;
103 mutex_unlock(&userspace_mutex);
104 break;
105 case CPUFREQ_GOV_LIMITS:
106 mutex_lock(&userspace_mutex);
107 pr_debug("limit event for cpu %u: %u - %u kHz, currently %u kHz, last set to %u kHz\n",
108 cpu, policy->min, policy->max, policy->cur, *setspeed);
109
110 if (policy->max < *setspeed)
111 __cpufreq_driver_target(policy, policy->max,
112 CPUFREQ_RELATION_H);
113 else if (policy->min > *setspeed)
114 __cpufreq_driver_target(policy, policy->min,
115 CPUFREQ_RELATION_L);
116 else
117 __cpufreq_driver_target(policy, *setspeed,
118 CPUFREQ_RELATION_L);
119 mutex_unlock(&userspace_mutex);
120 break;
121 }
122 return rc;
123 }
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