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