LXR linux/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
  18static int nr_devs = 4;
  19static int interval_ms = 10;
  20
  21module_param(nr_devs, int, 0400);
  22module_param(interval_ms, int, 0600);
  23
  24static struct stm_heartbeat {
  25        struct stm_source_data  data;
  26        struct hrtimer          hrtimer;
  27        unsigned int            active;
  28} stm_heartbeat[STM_HEARTBEAT_MAX];
  29
  30static const char str[] = "heartbeat stm source driver is here to serve you";
  31
  32static 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
  44static 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
  56static 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
  65static 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
  93fail_unregister:
  94        for (i--; i >= 0; i--) {
  95                stm_source_unregister_device(&stm_heartbeat[i].data);
  96fail_free:
  97                kfree(stm_heartbeat[i].data.name);
  98        }
  99
 100        return ret;
 101}
 102
 103static 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
 113module_init(stm_heartbeat_init);
 114module_exit(stm_heartbeat_exit);
 115
 116MODULE_LICENSE("GPL v2");
 117MODULE_DESCRIPTION("stm_heartbeat driver");
 118MODULE_AUTHOR("Alexander Shishkin <alexander.shishkin@linux.intel.com>");
 119