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 extern void (*tick_funcs[MAX_NUM_TICK_TASKS])(void);
  46
  47 /* Nescessary logic:
  48  * 1) All threads must pass unblocked
  49  * 2) Current handler must always pass unblocked
  50  * 3) Threads must be excluded when irq routine is running
  51  * 4) No more than one handler routine should execute at a time
  52  */
  53 int set_irq_level(int level)
  54 {
  55     SDL_LockMutex(sim_irq_mtx);
  56
  57     int oldlevel = interrupt_level;
  58
  59     if (status_reg == 0 && level == 0 && oldlevel != 0)
  60     {
  61         /* Not in a handler and "interrupts" are being reenabled */
  62         if (handlers_pending > 0)
  63             SDL_CondSignal(sim_thread_cond);
  64     }
  65
  66     interrupt_level = level; /* save new level */
  67
  68     SDL_UnlockMutex(sim_irq_mtx);
  69     return oldlevel;
  70 }
  71
  72 void sim_enter_irq_handler(void)
  73 {
  74     SDL_LockMutex(sim_irq_mtx);
  75     handlers_pending++;
  76
  77     if(interrupt_level != 0)
  78     {
  79         /* "Interrupts" are disabled. Wait for reenable */
  80         SDL_CondWait(sim_thread_cond, sim_irq_mtx);
  81     }
  82
  83     status_reg = 1;
  84 }
  85
  86 void sim_exit_irq_handler(void)
  87 {
  88     if (--handlers_pending > 0)
  89         SDL_CondSignal(sim_thread_cond);
  90
  91     status_reg = 0;
  92     SDL_UnlockMutex(sim_irq_mtx);
  93 }
  94
  95 bool sim_kernel_init(void)
  96 {
  97     sim_irq_mtx = SDL_CreateMutex();
  98     if (sim_irq_mtx == NULL)
  99     {
 100         fprintf(stderr, "Cannot create sim_handler_mtx\n");
 101         return false;
 102     }
 103
 104     sim_thread_cond = SDL_CreateCond();
 105     if (sim_thread_cond == NULL)
 106     {
 107         fprintf(stderr, "Cannot create sim_thread_cond\n");
 108         return false;
 109     }
 110
 111     return true;
 112 }
 113
 114 void sim_kernel_shutdown(void)
 115 {
 116     SDL_RemoveTimer(tick_timer_id);
 117     SDL_DestroyMutex(sim_irq_mtx);
 118     SDL_DestroyCond(sim_thread_cond);
 119 }
 120
 121 Uint32 tick_timer(Uint32 interval, void *param)
 122 {
 123     long new_tick;
 124
 125     (void) interval;
 126     (void) param;
 127
 128     new_tick = (SDL_GetTicks() - start_tick) / (1000/HZ);
 129
 130     if(new_tick != current_tick)
 131     {
 132         long t;
 133         for(t = new_tick - current_tick; t > 0; t--)
 134         {
 135             int i;
 136
 137             sim_enter_irq_handler();
 138
 139             /* Run through the list of tick tasks */
 140             for(i = 0;i < MAX_NUM_TICK_TASKS;i++)
 141             {
 142                 if(tick_funcs[i])
 143                 {
 144                     tick_funcs[i]();
 145                 }
 146             }
 147
 148             sim_exit_irq_handler();
 149         }
 150
 151         current_tick = new_tick;
 152     }
 153
 154     return 1;
 155 }
 156
 157 void tick_start(unsigned int interval_in_ms)
 158 {
 159     if (tick_timer_id != NULL)
 160     {
 161         SDL_RemoveTimer(tick_timer_id);
 162         tick_timer_id = NULL;
 163     }
 164     else
 165     {
 166         start_tick = SDL_GetTicks();
 167     }
 168
 169     tick_timer_id = SDL_AddTimer(interval_in_ms, tick_timer, NULL);
 170 }