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                 .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
  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
  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
  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
  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
  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>");