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 <inttypes.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 /* Level: 0 = enabled, not 0 = disabled */
  43 static int volatile interrupt_level = HIGHEST_IRQ_LEVEL;
  44 /* How many handers waiting? Not strictly needed because CondSignal is a
  45  * noop if no threads were waiting but it filters-out calls to functions
  46  * with higher overhead and provides info when debugging. */
  47 static int handlers_pending = 0;
  48 /* 1 = executing a handler; prevents CondSignal calls in set_irq_level
  49  * while in a handler */
  50 static int status_reg = 0;
  51
  52 /* Nescessary logic:
  53  * 1) All threads must pass unblocked
  54  * 2) Current handler must always pass unblocked
  55  * 3) Threads must be excluded when irq routine is running
  56  * 4) No more than one handler routine should execute at a time
  57  */
  58 int set_irq_level(int level)
  59 {
  60     SDL_LockMutex(sim_irq_mtx);
  61
  62     int oldlevel = interrupt_level;
  63
  64     if (status_reg == 0 && level == 0 && oldlevel != 0)
  65     {
  66         /* Not in a handler and "interrupts" are going from disabled to
  67          * enabled; signal any pending handlers still waiting */
  68         if (handlers_pending > 0)
  69             SDL_CondSignal(sim_thread_cond);
  70     }
  71
  72     interrupt_level = level; /* save new level */
  73
  74     SDL_UnlockMutex(sim_irq_mtx);
  75     return oldlevel;
  76 }
  77
  78 void sim_enter_irq_handler(void)
  79 {
  80     SDL_LockMutex(sim_irq_mtx);
  81     handlers_pending++;
  82
  83     /* Check each time before proceeding: disabled->enabled->...->disabled
  84      * is possible on an app thread before a handler thread is ever granted
  85      * the mutex; a handler can also leave "interrupts" disabled during
  86      * its execution */
  87     while (interrupt_level != 0)
  88         SDL_CondWait(sim_thread_cond, sim_irq_mtx);
  89
  90     status_reg = 1;
  91 }
  92
  93 void sim_exit_irq_handler(void)
  94 {
  95     /* If any others are waiting, give the signal */
  96     if (--handlers_pending > 0)
  97         SDL_CondSignal(sim_thread_cond);
  98
  99     status_reg = 0;
 100     SDL_UnlockMutex(sim_irq_mtx);
 101 }
 102
 103 static bool sim_kernel_init(void)
 104 {
 105     sim_irq_mtx = SDL_CreateMutex();
 106     if (sim_irq_mtx == NULL)
 107     {
 108         panicf("Cannot create sim_handler_mtx\n");
 109         return false;
 110     }
 111
 112     sim_thread_cond = SDL_CreateCond();
 113     if (sim_thread_cond == NULL)
 114     {
 115         panicf("Cannot create sim_thread_cond\n");
 116         return false;
 117     }
 118
 119     return true;
 120 }
 121
 122 void sim_kernel_shutdown(void)
 123 {
 124     SDL_RemoveTimer(tick_timer_id);
 125     SDL_DestroyMutex(sim_irq_mtx);
 126     SDL_DestroyCond(sim_thread_cond);
 127 }
 128
 129 Uint32 tick_timer(Uint32 interval, void *param)
 130 {
 131     long new_tick;
 132
 133     (void) interval;
 134     (void) param;
 135
 136     new_tick = (SDL_GetTicks() - start_tick) / (1000/HZ);
 137
 138     while(new_tick != current_tick)
 139     {
 140         sim_enter_irq_handler();
 141
 142         /* Run through the list of tick tasks - increments tick
 143          * on each iteration. */
 144         call_tick_tasks();
 145
 146         sim_exit_irq_handler();
 147     }
 148
 149     return interval;
 150 }
 151
 152 void tick_start(unsigned int interval_in_ms)
 153 {
 154     if (!sim_kernel_init())
 155     {
 156         panicf("Could not initialize kernel!");
 157         exit(-1);
 158     }
 159
 160     if (tick_timer_id != NULL)
 161     {
 162         SDL_RemoveTimer(tick_timer_id);
 163         tick_timer_id = NULL;
 164     }
 165     else
 166     {
 167         start_tick = SDL_GetTicks();
 168     }
 169
 170     tick_timer_id = SDL_AddTimer(interval_in_ms, tick_timer, NULL);
 171 }