1 // SPDX-License-Identifier: GPL-2.0
2 /*
3  * Scheduler code and data structures related to cpufreq.
4  *
5  * Copyright (C) 2016, Intel Corporation
6  * Author: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
7  */
8 
9 DEFINE_PER_CPU(struct update_util_data __rcu *, cpufreq_update_util_data);
10 
11 /**
12  * cpufreq_add_update_util_hook - Populate the CPU's update_util_data pointer.
13  * @cpu: The CPU to set the pointer for.
14  * @data: New pointer value.
15  * @func: Callback function to set for the CPU.
16  *
17  * Set and publish the update_util_data pointer for the given CPU.
18  *
19  * The update_util_data pointer of @cpu is set to @data and the callback
20  * function pointer in the target struct update_util_data is set to @func.
21  * That function will be called by cpufreq_update_util() from RCU-sched
22  * read-side critical sections, so it must not sleep.  @data will always be
23  * passed to it as the first argument which allows the function to get to the
24  * target update_util_data structure and its container.
25  *
26  * The update_util_data pointer of @cpu must be NULL when this function is
27  * called or it will WARN() and return with no effect.
28  */
cpufreq_add_update_util_hook(int cpu,struct update_util_data * data,void (* func)(struct update_util_data * data,u64 time,unsigned int flags))29 void cpufreq_add_update_util_hook(int cpu, struct update_util_data *data,
30 			void (*func)(struct update_util_data *data, u64 time,
31 				     unsigned int flags))
32 {
33 	if (WARN_ON(!data || !func))
34 		return;
35 
36 	if (WARN_ON(per_cpu(cpufreq_update_util_data, cpu)))
37 		return;
38 
39 	data->func = func;
40 	rcu_assign_pointer(per_cpu(cpufreq_update_util_data, cpu), data);
41 }
42 EXPORT_SYMBOL_GPL(cpufreq_add_update_util_hook);
43 
44 /**
45  * cpufreq_remove_update_util_hook - Clear the CPU's update_util_data pointer.
46  * @cpu: The CPU to clear the pointer for.
47  *
48  * Clear the update_util_data pointer for the given CPU.
49  *
50  * Callers must use RCU callbacks to free any memory that might be
51  * accessed via the old update_util_data pointer or invoke synchronize_rcu()
52  * right after this function to avoid use-after-free.
53  */
cpufreq_remove_update_util_hook(int cpu)54 void cpufreq_remove_update_util_hook(int cpu)
55 {
56 	rcu_assign_pointer(per_cpu(cpufreq_update_util_data, cpu), NULL);
57 }
58 EXPORT_SYMBOL_GPL(cpufreq_remove_update_util_hook);
59 
60 /**
61  * cpufreq_this_cpu_can_update - Check if cpufreq policy can be updated.
62  * @policy: cpufreq policy to check.
63  *
64  * Return 'true' if:
65  * - the local and remote CPUs share @policy,
66  * - dvfs_possible_from_any_cpu is set in @policy and the local CPU is not going
67  *   offline (in which case it is not expected to run cpufreq updates any more).
68  */
cpufreq_this_cpu_can_update(struct cpufreq_policy * policy)69 bool cpufreq_this_cpu_can_update(struct cpufreq_policy *policy)
70 {
71 	return cpumask_test_cpu(smp_processor_id(), policy->cpus) ||
72 		(policy->dvfs_possible_from_any_cpu &&
73 		 rcu_dereference_sched(*this_cpu_ptr(&cpufreq_update_util_data)));
74 }
75