1// SPDX-License-Identifier: GPL-2.0
2/*
3 * cpuidle driver for haltpoll governor.
4 *
5 * Copyright 2019 Red Hat, Inc. and/or its affiliates.
6 *
7 * This work is licensed under the terms of the GNU GPL, version 2. See
8 * the COPYING file in the top-level directory.
9 *
10 * Authors: Marcelo Tosatti <mtosatti@redhat.com>
11 */
12
13#include <linux/init.h>
14#include <linux/cpu.h>
15#include <linux/cpuidle.h>
16#include <linux/module.h>
17#include <linux/sched/idle.h>
18#include <linux/kvm_para.h>
19#include <linux/cpuidle_haltpoll.h>
20
21static bool force __read_mostly;
22module_param(force, bool, 0444);
23MODULE_PARM_DESC(force, "Load unconditionally");
24
25static struct cpuidle_device __percpu *haltpoll_cpuidle_devices;
26static enum cpuhp_state haltpoll_hp_state;
27
28static int default_enter_idle(struct cpuidle_device *dev,
29 struct cpuidle_driver *drv, int index)
30{
31 if (current_clr_polling_and_test()) {
32 local_irq_enable();
33 return index;
34 }
35 arch_cpu_idle();
36 return index;
37}
38
39static struct cpuidle_driver haltpoll_driver = {
40 .name = "haltpoll",
41 .governor = "haltpoll",
42 .states = {
43 { /* entry 0 is for polling */ },
44 {
45 .enter = default_enter_idle,
46 .exit_latency = 1,
47 .target_residency = 1,
48 .power_usage = -1,
49 .name = "haltpoll idle",
50 .desc = "default architecture idle",
51 },
52 },
53 .safe_state_index = 0,
54 .state_count = 2,
55};
56
57static int haltpoll_cpu_online(unsigned int cpu)
58{
59 struct cpuidle_device *dev;
60
61 dev = per_cpu_ptr(haltpoll_cpuidle_devices, cpu);
62 if (!dev->registered) {
63 dev->cpu = cpu;
64 if (cpuidle_register_device(dev)) {
65 pr_notice("cpuidle_register_device %d failed!\n", cpu);
66 return -EIO;
67 }
68 arch_haltpoll_enable(cpu);
69 }
70
71 return 0;
72}
73
74static int haltpoll_cpu_offline(unsigned int cpu)
75{
76 struct cpuidle_device *dev;
77
78 dev = per_cpu_ptr(haltpoll_cpuidle_devices, cpu);
79 if (dev->registered) {
80 arch_haltpoll_disable(cpu);
81 cpuidle_unregister_device(dev);
82 }
83
84 return 0;
85}
86
87static void haltpoll_uninit(void)
88{
89 if (haltpoll_hp_state)
90 cpuhp_remove_state(state: haltpoll_hp_state);
91 cpuidle_unregister_driver(drv: &haltpoll_driver);
92
93 free_percpu(pdata: haltpoll_cpuidle_devices);
94 haltpoll_cpuidle_devices = NULL;
95}
96
97static bool haltpoll_want(void)
98{
99 return kvm_para_has_hint(KVM_HINTS_REALTIME) || force;
100}
101
102static int __init haltpoll_init(void)
103{
104 int ret;
105 struct cpuidle_driver *drv = &haltpoll_driver;
106
107 /* Do not load haltpoll if idle= is passed */
108 if (boot_option_idle_override != IDLE_NO_OVERRIDE)
109 return -ENODEV;
110
111 if (!kvm_para_available() || !haltpoll_want())
112 return -ENODEV;
113
114 cpuidle_poll_state_init(drv);
115
116 ret = cpuidle_register_driver(drv);
117 if (ret < 0)
118 return ret;
119
120 haltpoll_cpuidle_devices = alloc_percpu(struct cpuidle_device);
121 if (haltpoll_cpuidle_devices == NULL) {
122 cpuidle_unregister_driver(drv);
123 return -ENOMEM;
124 }
125
126 ret = cpuhp_setup_state(state: CPUHP_AP_ONLINE_DYN, name: "cpuidle/haltpoll:online",
127 startup: haltpoll_cpu_online, teardown: haltpoll_cpu_offline);
128 if (ret < 0) {
129 haltpoll_uninit();
130 } else {
131 haltpoll_hp_state = ret;
132 ret = 0;
133 }
134
135 return ret;
136}
137
138static void __exit haltpoll_exit(void)
139{
140 haltpoll_uninit();
141}
142
143module_init(haltpoll_init);
144module_exit(haltpoll_exit);
145MODULE_LICENSE("GPL");
146MODULE_AUTHOR("Marcelo Tosatti <mtosatti@redhat.com>");
147

source code of linux/drivers/cpuidle/cpuidle-haltpoll.c