1// SPDX-License-Identifier: GPL-2.0
2/**
3 * @file nmi_timer_int.c
4 *
5 * @remark Copyright 2011 Advanced Micro Devices, Inc.
6 *
7 * @author Robert Richter <robert.richter@amd.com>
8 */
9
10#include <linux/init.h>
11#include <linux/smp.h>
12#include <linux/errno.h>
13#include <linux/oprofile.h>
14#include <linux/perf_event.h>
15
16#ifdef CONFIG_OPROFILE_NMI_TIMER
17
18static DEFINE_PER_CPU(struct perf_event *, nmi_timer_events);
19static int ctr_running;
20
21static struct perf_event_attr nmi_timer_attr = {
22	.type           = PERF_TYPE_HARDWARE,
23	.config         = PERF_COUNT_HW_CPU_CYCLES,
24	.size           = sizeof(struct perf_event_attr),
25	.pinned         = 1,
26	.disabled       = 1,
27};
28
29static void nmi_timer_callback(struct perf_event *event,
30			       struct perf_sample_data *data,
31			       struct pt_regs *regs)
32{
33	event->hw.interrupts = 0;       /* don't throttle interrupts */
34	oprofile_add_sample(regs, 0);
35}
36
37static int nmi_timer_start_cpu(int cpu)
38{
39	struct perf_event *event = per_cpu(nmi_timer_events, cpu);
40
41	if (!event) {
42		event = perf_event_create_kernel_counter(&nmi_timer_attr, cpu, NULL,
43							 nmi_timer_callback, NULL);
44		if (IS_ERR(event))
45			return PTR_ERR(event);
46		per_cpu(nmi_timer_events, cpu) = event;
47	}
48
49	if (event && ctr_running)
50		perf_event_enable(event);
51
52	return 0;
53}
54
55static void nmi_timer_stop_cpu(int cpu)
56{
57	struct perf_event *event = per_cpu(nmi_timer_events, cpu);
58
59	if (event && ctr_running)
60		perf_event_disable(event);
61}
62
63static int nmi_timer_cpu_online(unsigned int cpu)
64{
65	nmi_timer_start_cpu(cpu);
66	return 0;
67}
68static int nmi_timer_cpu_predown(unsigned int cpu)
69{
70	nmi_timer_stop_cpu(cpu);
71	return 0;
72}
73
74static int nmi_timer_start(void)
75{
76	int cpu;
77
78	get_online_cpus();
79	ctr_running = 1;
80	for_each_online_cpu(cpu)
81		nmi_timer_start_cpu(cpu);
82	put_online_cpus();
83
84	return 0;
85}
86
87static void nmi_timer_stop(void)
88{
89	int cpu;
90
91	get_online_cpus();
92	for_each_online_cpu(cpu)
93		nmi_timer_stop_cpu(cpu);
94	ctr_running = 0;
95	put_online_cpus();
96}
97
98static enum cpuhp_state hp_online;
99
100static void nmi_timer_shutdown(void)
101{
102	struct perf_event *event;
103	int cpu;
104
105	cpuhp_remove_state(hp_online);
106	for_each_possible_cpu(cpu) {
107		event = per_cpu(nmi_timer_events, cpu);
108		if (!event)
109			continue;
110		perf_event_disable(event);
111		per_cpu(nmi_timer_events, cpu) = NULL;
112		perf_event_release_kernel(event);
113	}
114}
115
116static int nmi_timer_setup(void)
117{
118	int err;
119	u64 period;
120
121	/* clock cycles per tick: */
122	period = (u64)cpu_khz * 1000;
123	do_div(period, HZ);
124	nmi_timer_attr.sample_period = period;
125
126	err = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "oprofile/nmi:online",
127				nmi_timer_cpu_online, nmi_timer_cpu_predown);
128	if (err < 0) {
129		nmi_timer_shutdown();
130		return err;
131	}
132	hp_online = err;
133	return 0;
134}
135
136int __init op_nmi_timer_init(struct oprofile_operations *ops)
137{
138	int err = 0;
139
140	err = nmi_timer_setup();
141	if (err)
142		return err;
143	nmi_timer_shutdown();		/* only check, don't alloc */
144
145	ops->create_files	= NULL;
146	ops->setup		= nmi_timer_setup;
147	ops->shutdown		= nmi_timer_shutdown;
148	ops->start		= nmi_timer_start;
149	ops->stop		= nmi_timer_stop;
150	ops->cpu_type		= "timer";
151
152	printk(KERN_INFO "oprofile: using NMI timer interrupt.\n");
153
154	return 0;
155}
156
157#endif
158