uisimulator/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 <SDL.h>
  24 #include <SDL_thread.h>
  25 #include "memory.h"
  26 #include "system-sdl.h"
  27 #include "uisdl.h"
  28 #include "kernel.h"
  29 #include "thread-sdl.h"
  30 #include "thread.h"
  31 #include "debug.h"
  32
  33 static SDL_TimerID tick_timer_id;
  34 long start_tick;
  35
  36 /* Condition to signal that "interrupts" may proceed */
  37 static SDL_cond *sim_thread_cond;
  38 /* Mutex to serialize changing levels and exclude other threads while
  39  * inside a handler */
  40 static SDL_mutex *sim_irq_mtx;
  41 static int interrupt_level = HIGHEST_IRQ_LEVEL;
  42 static int handlers_pending = 0;
  43 static int status_reg = 0;
  44
  45 /* Nescessary logic:
  46  * 1) All threads must pass unblocked
  47  * 2) Current handler must always pass unblocked
  48  * 3) Threads must be excluded when irq routine is running
  49  * 4) No more than one handler routine should execute at a time
  50  */
  51 int set_irq_level(int level)
  52 {
  53     SDL_LockMutex(sim_irq_mtx);
  54
  55     int oldlevel = interrupt_level;
  56
  57     if (status_reg == 0 && level == 0 && oldlevel != 0)
  58     {
  59         /* Not in a handler and "interrupts" are being reenabled */
  60         if (handlers_pending > 0)
  61             SDL_CondSignal(sim_thread_cond);
  62     }
  63
  64     interrupt_level = level; /* save new level */
  65
  66     SDL_UnlockMutex(sim_irq_mtx);
  67     return oldlevel;
  68 }
  69
  70 void sim_enter_irq_handler(void)
  71 {
  72     SDL_LockMutex(sim_irq_mtx);
  73     handlers_pending++;
  74
  75     if(interrupt_level != 0)
  76     {
  77         /* "Interrupts" are disabled. Wait for reenable */
  78         SDL_CondWait(sim_thread_cond, sim_irq_mtx);
  79     }
  80
  81     status_reg = 1;
  82 }
  83
  84 void sim_exit_irq_handler(void)
  85 {
  86     if (--handlers_pending > 0)
  87         SDL_CondSignal(sim_thread_cond);
  88
  89     status_reg = 0;
  90     SDL_UnlockMutex(sim_irq_mtx);
  91 }
  92
  93 bool sim_kernel_init(void)
  94 {
  95     sim_irq_mtx = SDL_CreateMutex();
  96     if (sim_irq_mtx == NULL)
  97     {
  98         fprintf(stderr, "Cannot create sim_handler_mtx\n");
  99         return false;
 100     }
 101
 102     sim_thread_cond = SDL_CreateCond();
 103     if (sim_thread_cond == NULL)
 104     {
 105         fprintf(stderr, "Cannot create sim_thread_cond\n");
 106         return false;
 107     }
 108
 109     return true;
 110 }
 111
 112 void sim_kernel_shutdown(void)
 113 {
 114     SDL_RemoveTimer(tick_timer_id);
 115     SDL_DestroyMutex(sim_irq_mtx);
 116     SDL_DestroyCond(sim_thread_cond);
 117 }
 118
 119 Uint32 tick_timer(Uint32 interval, void *param)
 120 {
 121     long new_tick;
 122
 123     (void) interval;
 124     (void) param;
 125
 126     new_tick = (SDL_GetTicks() - start_tick) / (1000/HZ);
 127
 128     while(new_tick != current_tick)
 129     {
 130         sim_enter_irq_handler();
 131
 132         /* Run through the list of tick tasks - increments tick
 133          * on each iteration. */
 134         call_tick_tasks();
 135
 136         sim_exit_irq_handler();
 137     }
 138
 139     return 1;
 140 }
 141
 142 void tick_start(unsigned int interval_in_ms)
 143 {
 144     if (tick_timer_id != NULL)
 145     {
 146         SDL_RemoveTimer(tick_timer_id);
 147         tick_timer_id = NULL;
 148     }
 149     else
 150     {
 151         start_tick = SDL_GetTicks();
 152     }
 153
 154     tick_timer_id = SDL_AddTimer(interval_in_ms, tick_timer, NULL);
 155 }