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
18 static DEFINE_PER_CPU(struct perf_event *, nmi_timer_events);
19 static int ctr_running;
20
21 static 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
nmi_timer_callback(struct perf_event * event,struct perf_sample_data * data,struct pt_regs * regs)29 static 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
nmi_timer_start_cpu(int cpu)37 static 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
nmi_timer_stop_cpu(int cpu)55 static 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
nmi_timer_cpu_online(unsigned int cpu)63 static int nmi_timer_cpu_online(unsigned int cpu)
64 {
65 nmi_timer_start_cpu(cpu);
66 return 0;
67 }
nmi_timer_cpu_predown(unsigned int cpu)68 static int nmi_timer_cpu_predown(unsigned int cpu)
69 {
70 nmi_timer_stop_cpu(cpu);
71 return 0;
72 }
73
nmi_timer_start(void)74 static 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
nmi_timer_stop(void)87 static 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
98 static enum cpuhp_state hp_online;
99
nmi_timer_shutdown(void)100 static 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
nmi_timer_setup(void)116 static 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
op_nmi_timer_init(struct oprofile_operations * ops)136 int __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