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 EXPORT_PER_CPU_SYMBOL_GPL(cpufreq_update_util_data);
11
12 /**
13 * cpufreq_add_update_util_hook - Populate the CPU's update_util_data pointer.
14 * @cpu: The CPU to set the pointer for.
15 * @data: New pointer value.
16 * @func: Callback function to set for the CPU.
17 *
18 * Set and publish the update_util_data pointer for the given CPU.
19 *
20 * The update_util_data pointer of @cpu is set to @data and the callback
21 * function pointer in the target struct update_util_data is set to @func.
22 * That function will be called by cpufreq_update_util() from RCU-sched
23 * read-side critical sections, so it must not sleep. @data will always be
24 * passed to it as the first argument which allows the function to get to the
25 * target update_util_data structure and its container.
26 *
27 * The update_util_data pointer of @cpu must be NULL when this function is
28 * called or it will WARN() and return with no effect.
29 */
cpufreq_add_update_util_hook(int cpu,struct update_util_data * data,void (* func)(struct update_util_data * data,u64 time,unsigned int flags))30 void cpufreq_add_update_util_hook(int cpu, struct update_util_data *data,
31 void (*func)(struct update_util_data *data, u64 time,
32 unsigned int flags))
33 {
34 if (WARN_ON(!data || !func))
35 return;
36
37 if (WARN_ON(per_cpu(cpufreq_update_util_data, cpu)))
38 return;
39
40 data->func = func;
41 rcu_assign_pointer(per_cpu(cpufreq_update_util_data, cpu), data);
42 }
43 EXPORT_SYMBOL_GPL(cpufreq_add_update_util_hook);
44
45 /**
46 * cpufreq_remove_update_util_hook - Clear the CPU's update_util_data pointer.
47 * @cpu: The CPU to clear the pointer for.
48 *
49 * Clear the update_util_data pointer for the given CPU.
50 *
51 * Callers must use RCU callbacks to free any memory that might be
52 * accessed via the old update_util_data pointer or invoke synchronize_rcu()
53 * right after this function to avoid use-after-free.
54 */
cpufreq_remove_update_util_hook(int cpu)55 void cpufreq_remove_update_util_hook(int cpu)
56 {
57 rcu_assign_pointer(per_cpu(cpufreq_update_util_data, cpu), NULL);
58 }
59 EXPORT_SYMBOL_GPL(cpufreq_remove_update_util_hook);
60
61 /**
62 * cpufreq_this_cpu_can_update - Check if cpufreq policy can be updated.
63 * @policy: cpufreq policy to check.
64 *
65 * Return 'true' if:
66 * - the local and remote CPUs share @policy,
67 * - dvfs_possible_from_any_cpu is set in @policy and the local CPU is not going
68 * offline (in which case it is not expected to run cpufreq updates any more).
69 */
cpufreq_this_cpu_can_update(struct cpufreq_policy * policy)70 bool cpufreq_this_cpu_can_update(struct cpufreq_policy *policy)
71 {
72 return cpumask_test_cpu(smp_processor_id(), policy->cpus) ||
73 (policy->dvfs_possible_from_any_cpu &&
74 rcu_dereference_sched(*this_cpu_ptr(&cpufreq_update_util_data)));
75 }
76 EXPORT_SYMBOL_GPL(cpufreq_this_cpu_can_update);
77