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