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, 0600);
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 unsigned int nr_instances;
39 
40 static const char str[] = "heartbeat stm source driver is here to serve you";
41 
42 static enum hrtimer_restart stm_heartbeat_hrtimer_handler(struct hrtimer *hr)
43 {
44 	struct stm_heartbeat *heartbeat = container_of(hr, struct stm_heartbeat,
45 						       hrtimer);
46 
47 	stm_source_write(&heartbeat->data, 0, str, sizeof str);
48 	if (heartbeat->active)
49 		hrtimer_forward_now(hr, ms_to_ktime(interval_ms));
50 
51 	return heartbeat->active ? HRTIMER_RESTART : HRTIMER_NORESTART;
52 }
53 
54 static int stm_heartbeat_link(struct stm_source_data *data)
55 {
56 	struct stm_heartbeat *heartbeat =
57 		container_of(data, struct stm_heartbeat, data);
58 
59 	heartbeat->active = 1;
60 	hrtimer_start(&heartbeat->hrtimer, ms_to_ktime(interval_ms),
61 		      HRTIMER_MODE_ABS);
62 
63 	return 0;
64 }
65 
66 static void stm_heartbeat_unlink(struct stm_source_data *data)
67 {
68 	struct stm_heartbeat *heartbeat =
69 		container_of(data, struct stm_heartbeat, data);
70 
71 	heartbeat->active = 0;
72 	hrtimer_cancel(&heartbeat->hrtimer);
73 }
74 
75 static int stm_heartbeat_init(void)
76 {
77 	int i, ret = -ENOMEM, __nr_instances = ACCESS_ONCE(nr_devs);
78 
79 	if (__nr_instances < 0 || __nr_instances > STM_HEARTBEAT_MAX)
80 		return -EINVAL;
81 
82 	for (i = 0; i < __nr_instances; i++) {
83 		stm_heartbeat[i].data.name =
84 			kasprintf(GFP_KERNEL, "heartbeat.%d", i);
85 		if (!stm_heartbeat[i].data.name)
86 			goto fail_unregister;
87 
88 		stm_heartbeat[i].data.nr_chans	= 1;
89 		stm_heartbeat[i].data.link		= stm_heartbeat_link;
90 		stm_heartbeat[i].data.unlink	= stm_heartbeat_unlink;
91 		hrtimer_init(&stm_heartbeat[i].hrtimer, CLOCK_MONOTONIC,
92 			     HRTIMER_MODE_ABS);
93 		stm_heartbeat[i].hrtimer.function =
94 			stm_heartbeat_hrtimer_handler;
95 
96 		ret = stm_source_register_device(NULL, &stm_heartbeat[i].data);
97 		if (ret)
98 			goto fail_free;
99 	}
100 
101 	nr_instances = __nr_instances;
102 
103 	return 0;
104 
105 fail_unregister:
106 	for (i--; i >= 0; i--) {
107 		stm_source_unregister_device(&stm_heartbeat[i].data);
108 fail_free:
109 		kfree(stm_heartbeat[i].data.name);
110 	}
111 
112 	return ret;
113 }
114 
115 static void stm_heartbeat_exit(void)
116 {
117 	int i;
118 
119 	for (i = 0; i < nr_instances; i++) {
120 		stm_source_unregister_device(&stm_heartbeat[i].data);
121 		kfree(stm_heartbeat[i].data.name);
122 	}
123 }
124 
125 module_init(stm_heartbeat_init);
126 module_exit(stm_heartbeat_exit);
127 
128 MODULE_LICENSE("GPL v2");
129 MODULE_DESCRIPTION("stm_heartbeat driver");
130 MODULE_AUTHOR("Alexander Shishkin <alexander.shishkin@linux.intel.com>");
131