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 __cpuidle int default_enter_idle(struct cpuidle_device *dev,
29 struct cpuidle_driver *drv, int index)
30{
31 if (current_clr_polling_and_test())
32 return index;
33
34 arch_cpu_idle();
35 return index;
36}
37
38static struct cpuidle_driver haltpoll_driver = {
39 .name = "haltpoll",
40 .governor = "haltpoll",
41 .states = {
42 { /* entry 0 is for polling */ },
43 {
44 .enter = default_enter_idle,
45 .exit_latency = 1,
46 .target_residency = 1,
47 .power_usage = -1,
48 .name = "haltpoll idle",
49 .desc = "default architecture idle",
50 },
51 },
52 .safe_state_index = 0,
53 .state_count = 2,
54};
55
56static int haltpoll_cpu_online(unsigned int cpu)
57{
58 struct cpuidle_device *dev;
59
60 dev = per_cpu_ptr(haltpoll_cpuidle_devices, cpu);
61 if (!dev->registered) {
62 dev->cpu = cpu;
63 if (cpuidle_register_device(dev)) {
64 pr_notice("cpuidle_register_device %d failed!\n", cpu);
65 return -EIO;
66 }
67 arch_haltpoll_enable(cpu);
68 }
69
70 return 0;
71}
72
73static int haltpoll_cpu_offline(unsigned int cpu)
74{
75 struct cpuidle_device *dev;
76
77 dev = per_cpu_ptr(haltpoll_cpuidle_devices, cpu);
78 if (dev->registered) {
79 arch_haltpoll_disable(cpu);
80 cpuidle_unregister_device(dev);
81 }
82
83 return 0;
84}
85
86static void haltpoll_uninit(void)
87{
88 if (haltpoll_hp_state)
89 cpuhp_remove_state(state: haltpoll_hp_state);
90 cpuidle_unregister_driver(drv: &haltpoll_driver);
91
92 free_percpu(pdata: haltpoll_cpuidle_devices);
93 haltpoll_cpuidle_devices = NULL;
94}
95
96static bool haltpoll_want(void)
97{
98 return kvm_para_has_hint(KVM_HINTS_REALTIME) || force;
99}
100
101static int __init haltpoll_init(void)
102{
103 int ret;
104 struct cpuidle_driver *drv = &haltpoll_driver;
105
106 /* Do not load haltpoll if idle= is passed */
107 if (boot_option_idle_override != IDLE_NO_OVERRIDE)
108 return -ENODEV;
109
110 if (!kvm_para_available() || !haltpoll_want())
111 return -ENODEV;
112
113 cpuidle_poll_state_init(drv);
114
115 ret = cpuidle_register_driver(drv);
116 if (ret < 0)
117 return ret;
118
119 haltpoll_cpuidle_devices = alloc_percpu(struct cpuidle_device);
120 if (haltpoll_cpuidle_devices == NULL) {
121 cpuidle_unregister_driver(drv);
122 return -ENOMEM;
123 }
124
125 ret = cpuhp_setup_state(state: CPUHP_AP_ONLINE_DYN, name: "cpuidle/haltpoll:online",
126 startup: haltpoll_cpu_online, teardown: haltpoll_cpu_offline);
127 if (ret < 0) {
128 haltpoll_uninit();
129 } else {
130 haltpoll_hp_state = ret;
131 ret = 0;
132 }
133
134 return ret;
135}
136
137static void __exit haltpoll_exit(void)
138{
139 haltpoll_uninit();
140}
141
142module_init(haltpoll_init);
143module_exit(haltpoll_exit);
144MODULE_DESCRIPTION("cpuidle driver for haltpoll governor");
145MODULE_LICENSE("GPL");
146MODULE_AUTHOR("Marcelo Tosatti <mtosatti@redhat.com>");
147