drivers/hwtracing/stm/heartbeat.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * Simple heartbeat STM source driver
   4  * Copyright (c) 2016, Intel Corporation.
   5  *
   6  * Heartbeat STM source will send repetitive messages over STM devices to a
   7  * trace host.
   8  */
   9
  10 #include <linux/kernel.h>
  11 #include <linux/module.h>
  12 #include <linux/hrtimer.h>
  13 #include <linux/slab.h>
  14 #include <linux/stm.h>
  15
  16 #define STM_HEARTBEAT_MAX       32
  17
  18 static int nr_devs = 4;
  19 static int interval_ms = 10;
  20
  21 module_param(nr_devs, int, 0400);
  22 module_param(interval_ms, int, 0600);
  23
  24 static struct stm_heartbeat {
  25         struct stm_source_data  data;
  26         struct hrtimer          hrtimer;
  27         unsigned int            active;
  28 } stm_heartbeat[STM_HEARTBEAT_MAX];
  29
  30 static const char str[] = "heartbeat stm source driver is here to serve you";
  31
  32 static enum hrtimer_restart stm_heartbeat_hrtimer_handler(struct hrtimer *hr)
  33 {
  34         struct stm_heartbeat *heartbeat = container_of(hr, struct stm_heartbeat,
  35                                                        hrtimer);
  36
  37         stm_source_write(&heartbeat->data, 0, str, sizeof str);
  38         if (heartbeat->active)
  39                 hrtimer_forward_now(hr, ms_to_ktime(interval_ms));
  40
  41         return heartbeat->active ? HRTIMER_RESTART : HRTIMER_NORESTART;
  42 }
  43
  44 static int stm_heartbeat_link(struct stm_source_data *data)
  45 {
  46         struct stm_heartbeat *heartbeat =
  47                 container_of(data, struct stm_heartbeat, data);
  48
  49         heartbeat->active = 1;
  50         hrtimer_start(&heartbeat->hrtimer, ms_to_ktime(interval_ms),
  51                       HRTIMER_MODE_ABS);
  52
  53         return 0;
  54 }
  55
  56 static void stm_heartbeat_unlink(struct stm_source_data *data)
  57 {
  58         struct stm_heartbeat *heartbeat =
  59                 container_of(data, struct stm_heartbeat, data);
  60
  61         heartbeat->active = 0;
  62         hrtimer_cancel(&heartbeat->hrtimer);
  63 }
  64
  65 static int stm_heartbeat_init(void)
  66 {
  67         int i, ret = -ENOMEM;
  68
  69         if (nr_devs < 0 || nr_devs > STM_HEARTBEAT_MAX)
  70                 return -EINVAL;
  71
  72         for (i = 0; i < nr_devs; i++) {
  73                 stm_heartbeat[i].data.name =
  74                         kasprintf(GFP_KERNEL, "heartbeat.%d", i);
  75                 if (!stm_heartbeat[i].data.name)
  76                         goto fail_unregister;
  77
  78                 stm_heartbeat[i].data.nr_chans  = 1;
  79                 stm_heartbeat[i].data.link      = stm_heartbeat_link;
  80                 stm_heartbeat[i].data.unlink    = stm_heartbeat_unlink;
  81                 hrtimer_init(&stm_heartbeat[i].hrtimer, CLOCK_MONOTONIC,
  82                              HRTIMER_MODE_ABS);
  83                 stm_heartbeat[i].hrtimer.function =
  84                         stm_heartbeat_hrtimer_handler;
  85
  86                 ret = stm_source_register_device(NULL, &stm_heartbeat[i].data);
  87                 if (ret)
  88                         goto fail_free;
  89         }
  90
  91         return 0;
  92
  93 fail_unregister:
  94         for (i--; i >= 0; i--) {
  95                 stm_source_unregister_device(&stm_heartbeat[i].data);
  96 fail_free:
  97                 kfree(stm_heartbeat[i].data.name);
  98         }
  99
 100         return ret;
 101 }
 102
 103 static void stm_heartbeat_exit(void)
 104 {
 105         int i;
 106
 107         for (i = 0; i < nr_devs; i++) {
 108                 stm_source_unregister_device(&stm_heartbeat[i].data);
 109                 kfree(stm_heartbeat[i].data.name);
 110         }
 111 }
 112
 113 module_init(stm_heartbeat_init);
 114 module_exit(stm_heartbeat_exit);
 115
 116 MODULE_LICENSE("GPL v2");
 117 MODULE_DESCRIPTION("stm_heartbeat driver");
 118 MODULE_AUTHOR("Alexander Shishkin <alexander.shishkin@linux.intel.com>");