1/**
2 * @file nmi_timer_int.c
3 *
4 * @remark Copyright 2011 Advanced Micro Devices, Inc.
5 *
6 * @author Robert Richter <robert.richter@amd.com>
7 */
8
9#include <linux/init.h>
10#include <linux/smp.h>
11#include <linux/errno.h>
12#include <linux/oprofile.h>
13#include <linux/perf_event.h>
14
15#ifdef CONFIG_OPROFILE_NMI_TIMER
16
17static DEFINE_PER_CPU(struct perf_event *, nmi_timer_events);
18static int ctr_running;
19
20static struct perf_event_attr nmi_timer_attr = {
21	.type           = PERF_TYPE_HARDWARE,
22	.config         = PERF_COUNT_HW_CPU_CYCLES,
23	.size           = sizeof(struct perf_event_attr),
24	.pinned         = 1,
25	.disabled       = 1,
26};
27
28static void nmi_timer_callback(struct perf_event *event,
29			       struct perf_sample_data *data,
30			       struct pt_regs *regs)
31{
32	event->hw.interrupts = 0;       /* don't throttle interrupts */
33	oprofile_add_sample(regs, 0);
34}
35
36static int nmi_timer_start_cpu(int cpu)
37{
38	struct perf_event *event = per_cpu(nmi_timer_events, cpu);
39
40	if (!event) {
41		event = perf_event_create_kernel_counter(&nmi_timer_attr, cpu, NULL,
42							 nmi_timer_callback, NULL);
43		if (IS_ERR(event))
44			return PTR_ERR(event);
45		per_cpu(nmi_timer_events, cpu) = event;
46	}
47
48	if (event && ctr_running)
49		perf_event_enable(event);
50
51	return 0;
52}
53
54static void nmi_timer_stop_cpu(int cpu)
55{
56	struct perf_event *event = per_cpu(nmi_timer_events, cpu);
57
58	if (event && ctr_running)
59		perf_event_disable(event);
60}
61
62static int nmi_timer_cpu_notifier(struct notifier_block *b, unsigned long action,
63				  void *data)
64{
65	int cpu = (unsigned long)data;
66	switch (action) {
67	case CPU_DOWN_FAILED:
68	case CPU_ONLINE:
69		nmi_timer_start_cpu(cpu);
70		break;
71	case CPU_DOWN_PREPARE:
72		nmi_timer_stop_cpu(cpu);
73		break;
74	}
75	return NOTIFY_DONE;
76}
77
78static struct notifier_block nmi_timer_cpu_nb = {
79	.notifier_call = nmi_timer_cpu_notifier
80};
81
82static int nmi_timer_start(void)
83{
84	int cpu;
85
86	get_online_cpus();
87	ctr_running = 1;
88	for_each_online_cpu(cpu)
89		nmi_timer_start_cpu(cpu);
90	put_online_cpus();
91
92	return 0;
93}
94
95static void nmi_timer_stop(void)
96{
97	int cpu;
98
99	get_online_cpus();
100	for_each_online_cpu(cpu)
101		nmi_timer_stop_cpu(cpu);
102	ctr_running = 0;
103	put_online_cpus();
104}
105
106static void nmi_timer_shutdown(void)
107{
108	struct perf_event *event;
109	int cpu;
110
111	cpu_notifier_register_begin();
112	__unregister_cpu_notifier(&nmi_timer_cpu_nb);
113	for_each_possible_cpu(cpu) {
114		event = per_cpu(nmi_timer_events, cpu);
115		if (!event)
116			continue;
117		perf_event_disable(event);
118		per_cpu(nmi_timer_events, cpu) = NULL;
119		perf_event_release_kernel(event);
120	}
121
122	cpu_notifier_register_done();
123}
124
125static int nmi_timer_setup(void)
126{
127	int cpu, err;
128	u64 period;
129
130	/* clock cycles per tick: */
131	period = (u64)cpu_khz * 1000;
132	do_div(period, HZ);
133	nmi_timer_attr.sample_period = period;
134
135	cpu_notifier_register_begin();
136	err = __register_cpu_notifier(&nmi_timer_cpu_nb);
137	if (err)
138		goto out;
139
140	/* can't attach events to offline cpus: */
141	for_each_online_cpu(cpu) {
142		err = nmi_timer_start_cpu(cpu);
143		if (err) {
144			cpu_notifier_register_done();
145			nmi_timer_shutdown();
146			return err;
147		}
148	}
149
150out:
151	cpu_notifier_register_done();
152	return err;
153}
154
155int __init op_nmi_timer_init(struct oprofile_operations *ops)
156{
157	int err = 0;
158
159	err = nmi_timer_setup();
160	if (err)
161		return err;
162	nmi_timer_shutdown();		/* only check, don't alloc */
163
164	ops->create_files	= NULL;
165	ops->setup		= nmi_timer_setup;
166	ops->shutdown		= nmi_timer_shutdown;
167	ops->start		= nmi_timer_start;
168	ops->stop		= nmi_timer_stop;
169	ops->cpu_type		= "timer";
170
171	printk(KERN_INFO "oprofile: using NMI timer interrupt.\n");
172
173	return 0;
174}
175
176#endif
177