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 
18 static int nr_devs = 4;
19 static int interval_ms = 10;
20 
21 module_param(nr_devs, int, 0400);
22 module_param(interval_ms, int, 0600);
23 
24 static struct stm_heartbeat {
25 	struct stm_source_data	data;
26 	struct hrtimer		hrtimer;
27 	unsigned int		active;
28 } stm_heartbeat[STM_HEARTBEAT_MAX];
29 
30 static const char str[] = "heartbeat stm source driver is here to serve you";
31 
32 static 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 
44 static 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 
56 static 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 
65 static int stm_heartbeat_init(void)
66 {
67 	int i, ret = -ENOMEM;
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 			goto fail_unregister;
77 
78 		stm_heartbeat[i].data.nr_chans	= 1;
79 		stm_heartbeat[i].data.link		= stm_heartbeat_link;
80 		stm_heartbeat[i].data.unlink	= stm_heartbeat_unlink;
81 		hrtimer_init(&stm_heartbeat[i].hrtimer, CLOCK_MONOTONIC,
82 			     HRTIMER_MODE_ABS);
83 		stm_heartbeat[i].hrtimer.function =
84 			stm_heartbeat_hrtimer_handler;
85 
86 		ret = stm_source_register_device(NULL, &stm_heartbeat[i].data);
87 		if (ret)
88 			goto fail_free;
89 	}
90 
91 	return 0;
92 
93 fail_unregister:
94 	for (i--; i >= 0; i--) {
95 		stm_source_unregister_device(&stm_heartbeat[i].data);
96 fail_free:
97 		kfree(stm_heartbeat[i].data.name);
98 	}
99 
100 	return ret;
101 }
102 
103 static void stm_heartbeat_exit(void)
104 {
105 	int i;
106 
107 	for (i = 0; i < nr_devs; i++) {
108 		stm_source_unregister_device(&stm_heartbeat[i].data);
109 		kfree(stm_heartbeat[i].data.name);
110 	}
111 }
112 
113 module_init(stm_heartbeat_init);
114 module_exit(stm_heartbeat_exit);
115 
116 MODULE_LICENSE("GPL v2");
117 MODULE_DESCRIPTION("stm_heartbeat driver");
118 MODULE_AUTHOR("Alexander Shishkin <alexander.shishkin@linux.intel.com>");
119