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(&heartbeat->data, 0, str, sizeof str);
38	if (heartbeat->active)
39		hrtimer_forward_now(hr, ms_to_ktime(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(&heartbeat->hrtimer, ms_to_ktime(interval_ms),
51		      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(&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, "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(&stm_heartbeat[i].hrtimer, CLOCK_MONOTONIC,
84			     HRTIMER_MODE_ABS);
85		stm_heartbeat[i].hrtimer.function =
86			stm_heartbeat_hrtimer_handler;
87
88		ret = stm_source_register_device(NULL, &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(&stm_heartbeat[i].data);
98fail_free:
99		kfree(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(&stm_heartbeat[i].data);
111		kfree(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