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	default_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(haltpoll_hp_state);
91	cpuidle_unregister_driver(&haltpoll_driver);
92
93	free_percpu(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	cpuidle_poll_state_init(drv);
112
113	if (!kvm_para_available() || !haltpoll_want())
114		return -ENODEV;
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(CPUHP_AP_ONLINE_DYN, "cpuidle/haltpoll:online",
127				haltpoll_cpu_online, 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