1 // SPDX-License-Identifier: GPL-2.0
2 /*
3 * Simple kernel driver to link kernel Ftrace and an STM device
4 * Copyright (c) 2016, Linaro Ltd.
5 *
6 * STM Ftrace will be registered as a trace_export.
7 */
8
9 #include <linux/module.h>
10 #include <linux/stm.h>
11 #include <linux/trace.h>
12
13 #define STM_FTRACE_NR_CHANNELS 1
14 #define STM_FTRACE_CHAN 0
15
16 static int stm_ftrace_link(struct stm_source_data *data);
17 static void stm_ftrace_unlink(struct stm_source_data *data);
18
19 static struct stm_ftrace {
20 struct stm_source_data data;
21 struct trace_export ftrace;
22 } stm_ftrace = {
23 .data = {
24 .name = "ftrace",
25 .nr_chans = STM_FTRACE_NR_CHANNELS,
26 .link = stm_ftrace_link,
27 .unlink = stm_ftrace_unlink,
28 },
29 };
30
31 /**
32 * stm_ftrace_write() - write data to STM via 'stm_ftrace' source
33 * @buf: buffer containing the data packet
34 * @len: length of the data packet
35 */
36 static void notrace
stm_ftrace_write(struct trace_export * export,const void * buf,unsigned int len)37 stm_ftrace_write(struct trace_export *export, const void *buf, unsigned int len)
38 {
39 struct stm_ftrace *stm = container_of(export, struct stm_ftrace, ftrace);
40 /* This is called from trace system with preemption disabled */
41 unsigned int cpu = smp_processor_id();
42
43 stm_source_write(&stm->data, STM_FTRACE_CHAN + cpu, buf, len);
44 }
45
stm_ftrace_link(struct stm_source_data * data)46 static int stm_ftrace_link(struct stm_source_data *data)
47 {
48 struct stm_ftrace *sf = container_of(data, struct stm_ftrace, data);
49
50 sf->ftrace.write = stm_ftrace_write;
51 sf->ftrace.flags = TRACE_EXPORT_FUNCTION | TRACE_EXPORT_EVENT
52 | TRACE_EXPORT_MARKER;
53
54 return register_ftrace_export(&sf->ftrace);
55 }
56
stm_ftrace_unlink(struct stm_source_data * data)57 static void stm_ftrace_unlink(struct stm_source_data *data)
58 {
59 struct stm_ftrace *sf = container_of(data, struct stm_ftrace, data);
60
61 unregister_ftrace_export(&sf->ftrace);
62 }
63
stm_ftrace_init(void)64 static int __init stm_ftrace_init(void)
65 {
66 int ret;
67
68 stm_ftrace.data.nr_chans = roundup_pow_of_two(num_possible_cpus());
69 ret = stm_source_register_device(NULL, &stm_ftrace.data);
70 if (ret)
71 pr_err("Failed to register stm_source - ftrace.\n");
72
73 return ret;
74 }
75
stm_ftrace_exit(void)76 static void __exit stm_ftrace_exit(void)
77 {
78 stm_source_unregister_device(&stm_ftrace.data);
79 }
80
81 module_init(stm_ftrace_init);
82 module_exit(stm_ftrace_exit);
83
84 MODULE_LICENSE("GPL v2");
85 MODULE_DESCRIPTION("stm_ftrace driver");
86 MODULE_AUTHOR("Chunyan Zhang <zhang.chunyan@linaro.org>");
87