1 /*
2  * Simple heartbeat STM source driver
3  * Copyright (c) 2016, Intel Corporation.
4  *
5  * This program is free software; you can redistribute it and/or modify it
6  * under the terms and conditions of the GNU General Public License,
7  * version 2, as published by the Free Software Foundation.
8  *
9  * This program is distributed in the hope it will be useful, but WITHOUT
10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
12  * more details.
13  *
14  * Heartbeat STM source will send repetitive messages over STM devices to a
15  * trace host.
16  */
17 
18 #include <linux/kernel.h>
19 #include <linux/module.h>
20 #include <linux/hrtimer.h>
21 #include <linux/slab.h>
22 #include <linux/stm.h>
23 
24 #define STM_HEARTBEAT_MAX	32
25 
26 static int nr_devs = 4;
27 static int interval_ms = 10;
28 
29 module_param(nr_devs, int, 0400);
30 module_param(interval_ms, int, 0600);
31 
32 static struct stm_heartbeat {
33 	struct stm_source_data	data;
34 	struct hrtimer		hrtimer;
35 	unsigned int		active;
36 } stm_heartbeat[STM_HEARTBEAT_MAX];
37 
38 static const char str[] = "heartbeat stm source driver is here to serve you";
39 
40 static enum hrtimer_restart stm_heartbeat_hrtimer_handler(struct hrtimer *hr)
41 {
42 	struct stm_heartbeat *heartbeat = container_of(hr, struct stm_heartbeat,
43 						       hrtimer);
44 
45 	stm_source_write(&heartbeat->data, 0, str, sizeof str);
46 	if (heartbeat->active)
47 		hrtimer_forward_now(hr, ms_to_ktime(interval_ms));
48 
49 	return heartbeat->active ? HRTIMER_RESTART : HRTIMER_NORESTART;
50 }
51 
52 static int stm_heartbeat_link(struct stm_source_data *data)
53 {
54 	struct stm_heartbeat *heartbeat =
55 		container_of(data, struct stm_heartbeat, data);
56 
57 	heartbeat->active = 1;
58 	hrtimer_start(&heartbeat->hrtimer, ms_to_ktime(interval_ms),
59 		      HRTIMER_MODE_ABS);
60 
61 	return 0;
62 }
63 
64 static void stm_heartbeat_unlink(struct stm_source_data *data)
65 {
66 	struct stm_heartbeat *heartbeat =
67 		container_of(data, struct stm_heartbeat, data);
68 
69 	heartbeat->active = 0;
70 	hrtimer_cancel(&heartbeat->hrtimer);
71 }
72 
73 static int stm_heartbeat_init(void)
74 {
75 	int i, ret = -ENOMEM;
76 
77 	if (nr_devs < 0 || nr_devs > STM_HEARTBEAT_MAX)
78 		return -EINVAL;
79 
80 	for (i = 0; i < nr_devs; i++) {
81 		stm_heartbeat[i].data.name =
82 			kasprintf(GFP_KERNEL, "heartbeat.%d", i);
83 		if (!stm_heartbeat[i].data.name)
84 			goto fail_unregister;
85 
86 		stm_heartbeat[i].data.nr_chans	= 1;
87 		stm_heartbeat[i].data.link		= stm_heartbeat_link;
88 		stm_heartbeat[i].data.unlink	= stm_heartbeat_unlink;
89 		hrtimer_init(&stm_heartbeat[i].hrtimer, CLOCK_MONOTONIC,
90 			     HRTIMER_MODE_ABS);
91 		stm_heartbeat[i].hrtimer.function =
92 			stm_heartbeat_hrtimer_handler;
93 
94 		ret = stm_source_register_device(NULL, &stm_heartbeat[i].data);
95 		if (ret)
96 			goto fail_free;
97 	}
98 
99 	return 0;
100 
101 fail_unregister:
102 	for (i--; i >= 0; i--) {
103 		stm_source_unregister_device(&stm_heartbeat[i].data);
104 fail_free:
105 		kfree(stm_heartbeat[i].data.name);
106 	}
107 
108 	return ret;
109 }
110 
111 static void stm_heartbeat_exit(void)
112 {
113 	int i;
114 
115 	for (i = 0; i < nr_devs; i++) {
116 		stm_source_unregister_device(&stm_heartbeat[i].data);
117 		kfree(stm_heartbeat[i].data.name);
118 	}
119 }
120 
121 module_init(stm_heartbeat_init);
122 module_exit(stm_heartbeat_exit);
123 
124 MODULE_LICENSE("GPL v2");
125 MODULE_DESCRIPTION("stm_heartbeat driver");
126 MODULE_AUTHOR("Alexander Shishkin <alexander.shishkin@linux.intel.com>");
127