drivers/hwtracing/stm/ftrace.c

   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
  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
  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
  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
  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
  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>");