firmware/target/hosted/sdl/kernel-sdl.c

   1 /***************************************************************************
   2  *             __________               __   ___.
   3  *   Open      \______   \ ____   ____ |  | _\_ |__   _______  ___
   4  *   Source     |       _//  _ \_/ ___\|  |/ /| __ \ /  _ \  \/  /
   5  *   Jukebox    |    |   (  <_> )  \___|    < | \_\ (  <_> > <  <
   6  *   Firmware   |____|_  /\____/ \___  >__|_ \|___  /\____/__/\_ \
   7  *                     \/            \/     \/    \/            \/
   8  * $Id$
   9  *
  10  * Copyright (C) 2002 by Felix Arends
  11  *
  12  * This program is free software; you can redistribute it and/or
  13  * modify it under the terms of the GNU General Public License
  14  * as published by the Free Software Foundation; either version 2
  15  * of the License, or (at your option) any later version.
  16  *
  17  * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
  18  * KIND, either express or implied.
  19  *
  20  ****************************************************************************/
  21
  22 #include <stdlib.h>
  23 #include <stdio.h>
  24 #include <SDL.h>
  25 #include <SDL_thread.h>
  26 #include "memory.h"
  27 #include "system-sdl.h"
  28 #include "thread-sdl.h"
  29 #include "kernel.h"
  30 #include "thread.h"
  31 #include "panic.h"
  32 #include "debug.h"
  33
  34 static SDL_TimerID tick_timer_id;
  35 long start_tick;
  36
  37 /* Condition to signal that "interrupts" may proceed */
  38 static SDL_cond *sim_thread_cond;
  39 /* Mutex to serialize changing levels and exclude other threads while
  40  * inside a handler */
  41 static SDL_mutex *sim_irq_mtx;
  42 static int interrupt_level = HIGHEST_IRQ_LEVEL;
  43 static int handlers_pending = 0;
  44 static int status_reg = 0;
  45
  46 /* Nescessary logic:
  47  * 1) All threads must pass unblocked
  48  * 2) Current handler must always pass unblocked
  49  * 3) Threads must be excluded when irq routine is running
  50  * 4) No more than one handler routine should execute at a time
  51  */
  52 int set_irq_level(int level)
  53 {
  54     SDL_LockMutex(sim_irq_mtx);
  55
  56     int oldlevel = interrupt_level;
  57
  58     if (status_reg == 0 && level == 0 && oldlevel != 0)
  59     {
  60         /* Not in a handler and "interrupts" are being reenabled */
  61         if (handlers_pending > 0)
  62             SDL_CondSignal(sim_thread_cond);
  63     }
  64
  65     interrupt_level = level; /* save new level */
  66
  67     SDL_UnlockMutex(sim_irq_mtx);
  68     return oldlevel;
  69 }
  70
  71 void sim_enter_irq_handler(void)
  72 {
  73     SDL_LockMutex(sim_irq_mtx);
  74     handlers_pending++;
  75
  76     if(interrupt_level != 0)
  77     {
  78         /* "Interrupts" are disabled. Wait for reenable */
  79         SDL_CondWait(sim_thread_cond, sim_irq_mtx);
  80     }
  81
  82     status_reg = 1;
  83 }
  84
  85 void sim_exit_irq_handler(void)
  86 {
  87     if (--handlers_pending > 0)
  88         SDL_CondSignal(sim_thread_cond);
  89
  90     status_reg = 0;
  91     SDL_UnlockMutex(sim_irq_mtx);
  92 }
  93
  94 static bool sim_kernel_init(void)
  95 {
  96     sim_irq_mtx = SDL_CreateMutex();
  97     if (sim_irq_mtx == NULL)
  98     {
  99         panicf("Cannot create sim_handler_mtx\n");
 100         return false;
 101     }
 102
 103     sim_thread_cond = SDL_CreateCond();
 104     if (sim_thread_cond == NULL)
 105     {
 106         panicf("Cannot create sim_thread_cond\n");
 107         return false;
 108     }
 109
 110     return true;
 111 }
 112
 113 void sim_kernel_shutdown(void)
 114 {
 115     SDL_RemoveTimer(tick_timer_id);
 116     SDL_DestroyMutex(sim_irq_mtx);
 117     SDL_DestroyCond(sim_thread_cond);
 118 }
 119
 120 Uint32 tick_timer(Uint32 interval, void *param)
 121 {
 122     long new_tick;
 123
 124     (void) interval;
 125     (void) param;
 126
 127     new_tick = (SDL_GetTicks() - start_tick) / (1000/HZ);
 128
 129     while(new_tick != current_tick)
 130     {
 131         sim_enter_irq_handler();
 132
 133         /* Run through the list of tick tasks - increments tick
 134          * on each iteration. */
 135         call_tick_tasks();
 136
 137         sim_exit_irq_handler();
 138     }
 139
 140     return 1;
 141 }
 142
 143 void tick_start(unsigned int interval_in_ms)
 144 {
 145     if (!sim_kernel_init())
 146     {
 147         panicf("Could not initialize kernel!");
 148         exit(-1);
 149     }
 150
 151     if (tick_timer_id != NULL)
 152     {
 153         SDL_RemoveTimer(tick_timer_id);
 154         tick_timer_id = NULL;
 155     }
 156     else
 157     {
 158         start_tick = SDL_GetTicks();
 159     }
 160
 161     tick_timer_id = SDL_AddTimer(interval_in_ms, tick_timer, NULL);
 162 }