provide disable_cpufreq() function to disable the API.

useful for disabling cpufreq altogether. The cpu frequency
scaling drivers and cpu frequency governors will fail to register.

Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Signed-off-by: Dave Jones <davej@redhat.com>

diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
index 622013f..7f2f149 100644 (file)
--- a/drivers/cpufreq/cpufreq.c
+++ b/drivers/cpufreq/cpufreq.c
@@ -126,6 +126,15 @@ static int __init init_cpufreq_transition_notifier_list(void)
 }
 pure_initcall(init_cpufreq_transition_notifier_list);
 
+static int off __read_mostly;
+int cpufreq_disabled(void)
+{
+       return off;
+}
+void disable_cpufreq(void)
+{
+       off = 1;
+}
 static LIST_HEAD(cpufreq_governor_list);
 static DEFINE_MUTEX(cpufreq_governor_mutex);
 
@@ -1441,6 +1450,9 @@ int __cpufreq_driver_target(struct cpufreq_policy *policy,
 {
        int retval = -EINVAL;
 
+       if (cpufreq_disabled())
+               return -ENODEV;
+
        pr_debug("target for CPU %u: %u kHz, relation %u\n", policy->cpu,
                target_freq, relation);
        if (cpu_online(policy->cpu) && cpufreq_driver->target)
@@ -1549,6 +1561,9 @@ int cpufreq_register_governor(struct cpufreq_governor *governor)
        if (!governor)
                return -EINVAL;
 
+       if (cpufreq_disabled())
+               return -ENODEV;
+
        mutex_lock(&cpufreq_governor_mutex);
 
        err = -EBUSY;
@@ -1572,6 +1587,9 @@ void cpufreq_unregister_governor(struct cpufreq_governor *governor)
        if (!governor)
                return;
 
+       if (cpufreq_disabled())
+               return;
+
 #ifdef CONFIG_HOTPLUG_CPU
        for_each_present_cpu(cpu) {
                if (cpu_online(cpu))
@@ -1814,6 +1832,9 @@ int cpufreq_register_driver(struct cpufreq_driver *driver_data)
        unsigned long flags;
        int ret;
 
+       if (cpufreq_disabled())
+               return -ENODEV;
+
        if (!driver_data || !driver_data->verify || !driver_data->init ||
            ((!driver_data->setpolicy) && (!driver_data->target)))
                return -EINVAL;
@@ -1901,6 +1922,9 @@ static int __init cpufreq_core_init(void)
 {
        int cpu;
 
+       if (cpufreq_disabled())
+               return -ENODEV;
+
        for_each_possible_cpu(cpu) {
                per_cpu(cpufreq_policy_cpu, cpu) = -1;
                init_rwsem(&per_cpu(cpu_policy_rwsem, cpu));

diff --git a/include/linux/cpufreq.h b/include/linux/cpufreq.h
index 6216115..8ff4427 100644 (file)
--- a/include/linux/cpufreq.h
+++ b/include/linux/cpufreq.h
@@ -35,6 +35,7 @@
 #ifdef CONFIG_CPU_FREQ
 int cpufreq_register_notifier(struct notifier_block *nb, unsigned int list);
 int cpufreq_unregister_notifier(struct notifier_block *nb, unsigned int list);
+extern void disable_cpufreq(void);
 #else          /* CONFIG_CPU_FREQ */
 static inline int cpufreq_register_notifier(struct notifier_block *nb,
                                                unsigned int list)
@@ -46,6 +47,7 @@ static inline int cpufreq_unregister_notifier(struct notifier_block *nb,
 {
        return 0;
 }
+static inline void disable_cpufreq(void) { }
 #endif         /* CONFIG_CPU_FREQ */
 
 /* if (cpufreq_driver->target) exists, the ->governor decides what frequency