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
16static int stm_ftrace_link(struct stm_source_data *data);
17static void stm_ftrace_unlink(struct stm_source_data *data);
18
19static 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 */
36static void notrace
37stm_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(data: &stm->data, STM_FTRACE_CHAN + cpu, buf, count: len);
44}
45
46static 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(export: &sf->ftrace);
55}
56
57static 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(export: &sf->ftrace);
62}
63
64static 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, data: &stm_ftrace.data);
70 if (ret)
71 pr_err("Failed to register stm_source - ftrace.\n");
72
73 return ret;
74}
75
76static void __exit stm_ftrace_exit(void)
77{
78 stm_source_unregister_device(data: &stm_ftrace.data);
79}
80
81module_init(stm_ftrace_init);
82module_exit(stm_ftrace_exit);
83
84MODULE_LICENSE("GPL v2");
85MODULE_DESCRIPTION("stm_ftrace driver");
86MODULE_AUTHOR("Chunyan Zhang <zhang.chunyan@linaro.org>");
87

source code of linux/drivers/hwtracing/stm/ftrace.c