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  * All files in this archive are subject to the GNU General Public License.
  13  * See the file COPYING in the source tree root for full license agreement.
  14  *
  15  * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
  16  * KIND, either express or implied.
  17  *
  18  ****************************************************************************/
  19
  20 #include <stdlib.h>
  21 #include <SDL.h>
  22 #include <SDL_thread.h>
  23 #include "memory.h"
  24 #include "system-sdl.h"
  25 #include "uisdl.h"
  26 #include "kernel.h"
  27 #include "thread-sdl.h"
  28 #include "thread.h"
  29 #include "debug.h"
  30
  31 static SDL_TimerID tick_timer_id;
  32 long start_tick;
  33
  34 /* Condition to signal that "interrupts" may proceed */
  35 static SDL_cond *sim_thread_cond;
  36 /* Mutex to serialize changing levels and exclude other threads while
  37  * inside a handler */
  38 static SDL_mutex *sim_irq_mtx;
  39 static int interrupt_level = HIGHEST_IRQ_LEVEL;
  40 static int handlers_pending = 0;
  41 static int status_reg = 0;
  42
  43 extern void (*tick_funcs[MAX_NUM_TICK_TASKS])(void);
  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     if(new_tick != current_tick)
 129     {
 130         long t;
 131         for(t = new_tick - current_tick; t > 0; t--)
 132         {
 133             int i;
 134
 135             sim_enter_irq_handler();
 136
 137             /* Run through the list of tick tasks */
 138             for(i = 0;i < MAX_NUM_TICK_TASKS;i++)
 139             {
 140                 if(tick_funcs[i])
 141                 {
 142                     tick_funcs[i]();
 143                 }
 144             }
 145
 146             sim_exit_irq_handler();
 147         }
 148
 149         current_tick = new_tick;
 150     }
 151
 152     return 1;
 153 }
 154
 155 void tick_start(unsigned int interval_in_ms)
 156 {
 157     if (tick_timer_id != NULL)
 158     {
 159         SDL_RemoveTimer(tick_timer_id);
 160         tick_timer_id = NULL;
 161     }
 162     else
 163     {
 164         start_tick = SDL_GetTicks();
 165     }
 166
 167     tick_timer_id = SDL_AddTimer(interval_in_ms, tick_timer, NULL);
 168 }