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 .type = STM_FTRACE,
27 .link = stm_ftrace_link,
28 .unlink = stm_ftrace_unlink,
29 },
30 };
31
32 /**
33 * stm_ftrace_write() - write data to STM via 'stm_ftrace' source
34 * @buf: buffer containing the data packet
35 * @len: length of the data packet
36 */
37 static void notrace
stm_ftrace_write(struct trace_export * export,const void * buf,unsigned int len)38 stm_ftrace_write(struct trace_export *export, const void *buf, unsigned int len)
39 {
40 struct stm_ftrace *stm = container_of(export, struct stm_ftrace, ftrace);
41 /* This is called from trace system with preemption disabled */
42 unsigned int cpu = smp_processor_id();
43
44 stm_source_write(&stm->data, STM_FTRACE_CHAN + cpu, buf, len);
45 }
46
stm_ftrace_link(struct stm_source_data * data)47 static int stm_ftrace_link(struct stm_source_data *data)
48 {
49 struct stm_ftrace *sf = container_of(data, struct stm_ftrace, data);
50
51 sf->ftrace.write = stm_ftrace_write;
52 sf->ftrace.flags = TRACE_EXPORT_FUNCTION | TRACE_EXPORT_EVENT
53 | TRACE_EXPORT_MARKER;
54
55 return register_ftrace_export(&sf->ftrace);
56 }
57
stm_ftrace_unlink(struct stm_source_data * data)58 static void stm_ftrace_unlink(struct stm_source_data *data)
59 {
60 struct stm_ftrace *sf = container_of(data, struct stm_ftrace, data);
61
62 unregister_ftrace_export(&sf->ftrace);
63 }
64
stm_ftrace_init(void)65 static int __init stm_ftrace_init(void)
66 {
67 int ret;
68
69 stm_ftrace.data.nr_chans = roundup_pow_of_two(num_possible_cpus());
70 ret = stm_source_register_device(NULL, &stm_ftrace.data);
71 if (ret)
72 pr_err("Failed to register stm_source - ftrace.\n");
73
74 return ret;
75 }
76
stm_ftrace_exit(void)77 static void __exit stm_ftrace_exit(void)
78 {
79 stm_source_unregister_device(&stm_ftrace.data);
80 }
81
82 module_init(stm_ftrace_init);
83 module_exit(stm_ftrace_exit);
84
85 MODULE_LICENSE("GPL v2");
86 MODULE_DESCRIPTION("stm_ftrace driver");
87 MODULE_AUTHOR("Chunyan Zhang <zhang.chunyan@linaro.org>");
88