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 
21 static struct cpuidle_device __percpu *haltpoll_cpuidle_devices;
22 static enum cpuhp_state haltpoll_hp_state;
23 
24 static int default_enter_idle(struct cpuidle_device *dev,
25 			      struct cpuidle_driver *drv, int index)
26 {
27 	if (current_clr_polling_and_test()) {
28 		local_irq_enable();
29 		return index;
30 	}
31 	default_idle();
32 	return index;
33 }
34 
35 static struct cpuidle_driver haltpoll_driver = {
36 	.name = "haltpoll",
37 	.governor = "haltpoll",
38 	.states = {
39 		{ /* entry 0 is for polling */ },
40 		{
41 			.enter			= default_enter_idle,
42 			.exit_latency		= 1,
43 			.target_residency	= 1,
44 			.power_usage		= -1,
45 			.name			= "haltpoll idle",
46 			.desc			= "default architecture idle",
47 		},
48 	},
49 	.safe_state_index = 0,
50 	.state_count = 2,
51 };
52 
53 static int haltpoll_cpu_online(unsigned int cpu)
54 {
55 	struct cpuidle_device *dev;
56 
57 	dev = per_cpu_ptr(haltpoll_cpuidle_devices, cpu);
58 	if (!dev->registered) {
59 		dev->cpu = cpu;
60 		if (cpuidle_register_device(dev)) {
61 			pr_notice("cpuidle_register_device %d failed!\n", cpu);
62 			return -EIO;
63 		}
64 		arch_haltpoll_enable(cpu);
65 	}
66 
67 	return 0;
68 }
69 
70 static int haltpoll_cpu_offline(unsigned int cpu)
71 {
72 	struct cpuidle_device *dev;
73 
74 	dev = per_cpu_ptr(haltpoll_cpuidle_devices, cpu);
75 	if (dev->registered) {
76 		arch_haltpoll_disable(cpu);
77 		cpuidle_unregister_device(dev);
78 	}
79 
80 	return 0;
81 }
82 
83 static void haltpoll_uninit(void)
84 {
85 	if (haltpoll_hp_state)
86 		cpuhp_remove_state(haltpoll_hp_state);
87 	cpuidle_unregister_driver(&haltpoll_driver);
88 
89 	free_percpu(haltpoll_cpuidle_devices);
90 	haltpoll_cpuidle_devices = NULL;
91 }
92 
93 static int __init haltpoll_init(void)
94 {
95 	int ret;
96 	struct cpuidle_driver *drv = &haltpoll_driver;
97 
98 	/* Do not load haltpoll if idle= is passed */
99 	if (boot_option_idle_override != IDLE_NO_OVERRIDE)
100 		return -ENODEV;
101 
102 	cpuidle_poll_state_init(drv);
103 
104 	if (!kvm_para_available() ||
105 		!kvm_para_has_hint(KVM_HINTS_REALTIME))
106 		return -ENODEV;
107 
108 	ret = cpuidle_register_driver(drv);
109 	if (ret < 0)
110 		return ret;
111 
112 	haltpoll_cpuidle_devices = alloc_percpu(struct cpuidle_device);
113 	if (haltpoll_cpuidle_devices == NULL) {
114 		cpuidle_unregister_driver(drv);
115 		return -ENOMEM;
116 	}
117 
118 	ret = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "cpuidle/haltpoll:online",
119 				haltpoll_cpu_online, haltpoll_cpu_offline);
120 	if (ret < 0) {
121 		haltpoll_uninit();
122 	} else {
123 		haltpoll_hp_state = ret;
124 		ret = 0;
125 	}
126 
127 	return ret;
128 }
129 
130 static void __exit haltpoll_exit(void)
131 {
132 	haltpoll_uninit();
133 }
134 
135 module_init(haltpoll_init);
136 module_exit(haltpoll_exit);
137 MODULE_LICENSE("GPL");
138 MODULE_AUTHOR("Marcelo Tosatti <mtosatti@redhat.com>");
139