1// SPDX-License-Identifier: GPL-2.0
2/*
3 * Simple heartbeat STM source driver
4 * Copyright (c) 2016, Intel Corporation.
5 *
6 * Heartbeat STM source will send repetitive messages over STM devices to a
7 * trace host.
8 */
9
10#include <linux/kernel.h>
11#include <linux/module.h>
12#include <linux/hrtimer.h>
13#include <linux/slab.h>
14#include <linux/stm.h>
15
16#define STM_HEARTBEAT_MAX 32
17
18static int nr_devs = 4;
19static int interval_ms = 10;
20
21module_param(nr_devs, int, 0400);
22module_param(interval_ms, int, 0600);
23
24static struct stm_heartbeat {
25 struct stm_source_data data;
26 struct hrtimer hrtimer;
27 unsigned int active;
28} stm_heartbeat[STM_HEARTBEAT_MAX];
29
30static const char str[] = "heartbeat stm source driver is here to serve you";
31
32static enum hrtimer_restart stm_heartbeat_hrtimer_handler(struct hrtimer *hr)
33{
34 struct stm_heartbeat *heartbeat = container_of(hr, struct stm_heartbeat,
35 hrtimer);
36
37 stm_source_write(data: &heartbeat->data, chan: 0, buf: str, count: sizeof str);
38 if (heartbeat->active)
39 hrtimer_forward_now(timer: hr, interval: ms_to_ktime(ms: interval_ms));
40
41 return heartbeat->active ? HRTIMER_RESTART : HRTIMER_NORESTART;
42}
43
44static int stm_heartbeat_link(struct stm_source_data *data)
45{
46 struct stm_heartbeat *heartbeat =
47 container_of(data, struct stm_heartbeat, data);
48
49 heartbeat->active = 1;
50 hrtimer_start(timer: &heartbeat->hrtimer, tim: ms_to_ktime(ms: interval_ms),
51 mode: HRTIMER_MODE_ABS);
52
53 return 0;
54}
55
56static void stm_heartbeat_unlink(struct stm_source_data *data)
57{
58 struct stm_heartbeat *heartbeat =
59 container_of(data, struct stm_heartbeat, data);
60
61 heartbeat->active = 0;
62 hrtimer_cancel(timer: &heartbeat->hrtimer);
63}
64
65static int stm_heartbeat_init(void)
66{
67 int i, ret;
68
69 if (nr_devs < 0 || nr_devs > STM_HEARTBEAT_MAX)
70 return -EINVAL;
71
72 for (i = 0; i < nr_devs; i++) {
73 stm_heartbeat[i].data.name =
74 kasprintf(GFP_KERNEL, fmt: "heartbeat.%d", i);
75 if (!stm_heartbeat[i].data.name) {
76 ret = -ENOMEM;
77 goto fail_unregister;
78 }
79
80 stm_heartbeat[i].data.nr_chans = 1;
81 stm_heartbeat[i].data.link = stm_heartbeat_link;
82 stm_heartbeat[i].data.unlink = stm_heartbeat_unlink;
83 hrtimer_init(timer: &stm_heartbeat[i].hrtimer, CLOCK_MONOTONIC,
84 mode: HRTIMER_MODE_ABS);
85 stm_heartbeat[i].hrtimer.function =
86 stm_heartbeat_hrtimer_handler;
87
88 ret = stm_source_register_device(NULL, data: &stm_heartbeat[i].data);
89 if (ret)
90 goto fail_free;
91 }
92
93 return 0;
94
95fail_unregister:
96 for (i--; i >= 0; i--) {
97 stm_source_unregister_device(data: &stm_heartbeat[i].data);
98fail_free:
99 kfree(objp: stm_heartbeat[i].data.name);
100 }
101
102 return ret;
103}
104
105static void stm_heartbeat_exit(void)
106{
107 int i;
108
109 for (i = 0; i < nr_devs; i++) {
110 stm_source_unregister_device(data: &stm_heartbeat[i].data);
111 kfree(objp: stm_heartbeat[i].data.name);
112 }
113}
114
115module_init(stm_heartbeat_init);
116module_exit(stm_heartbeat_exit);
117
118MODULE_LICENSE("GPL v2");
119MODULE_DESCRIPTION("stm_heartbeat driver");
120MODULE_AUTHOR("Alexander Shishkin <alexander.shishkin@linux.intel.com>");
121

source code of linux/drivers/hwtracing/stm/heartbeat.c