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	get_online_cpus();
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	put_online_cpus();
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	get_online_cpus();
136	err = register_cpu_notifier(&nmi_timer_cpu_nb);
137	if (err)
138		goto out;
139	/* can't attach events to offline cpus: */
140	for_each_online_cpu(cpu) {
141		err = nmi_timer_start_cpu(cpu);
142		if (err)
143			break;
144	}
145	if (err)
146		nmi_timer_shutdown();
147out:
148	put_online_cpus();
149	return err;
150}
151
152int __init op_nmi_timer_init(struct oprofile_operations *ops)
153{
154	int err = 0;
155
156	err = nmi_timer_setup();
157	if (err)
158		return err;
159	nmi_timer_shutdown();		/* only check, don't alloc */
160
161	ops->create_files	= NULL;
162	ops->setup		= nmi_timer_setup;
163	ops->shutdown		= nmi_timer_shutdown;
164	ops->start		= nmi_timer_start;
165	ops->stop		= nmi_timer_stop;
166	ops->cpu_type		= "timer";
167
168	printk(KERN_INFO "oprofile: using NMI timer interrupt.\n");
169
170	return 0;
171}
172
173#endif