git.mutantstargoat.com Git - dosdemo/blob - src/dos/timer.c

   1 /* for sound we use MIDAS, which takes over the PIT and we can't use it
   2  * therefore only compile this file for NO_SOUND builds.
   3  */
   4 #ifdef NO_SOUND
   5
   6 #include <stdio.h>
   7 #include <stdlib.h>
   8 #include <assert.h>
   9 #include <conio.h>
  10 #include <dos.h>
  11
  12 #ifdef __WATCOMC__
  13 #include <i86.h>
  14 #endif
  15
  16 #ifdef __DJGPP__
  17 #include <dpmi.h>
  18 #include <go32.h>
  19 #include <pc.h>
  20 #endif
  21
  22 #include "pit8254.h"
  23 #include "inttypes.h"
  24 #include "util.h"
  25
  26 #define PIT_TIMER_INTR  8
  27 #define DOS_TIMER_INTR  0x1c
  28
  29 /* macro to divide and round to the nearest integer */
  30 #define DIV_ROUND(a, b) \
  31         ((a) / (b) + ((a) % (b)) / ((b) / 2))
  32
  33 static void set_timer_reload(int reload_val);
  34 static void cleanup(void);
  35
  36 #ifdef __WATCOMC__
  37 #define INTERRUPT       __interrupt __far
  38
  39 static void INTERRUPT dos_timer_intr();
  40
  41 static void (INTERRUPT *prev_timer_intr)();
  42 #endif
  43
  44 #ifdef __DJGPP__
  45 #define INTERRUPT
  46
  47 static _go32_dpmi_seginfo intr, prev_intr;
  48
  49 #define outp(p, v)      outportb(p, v)
  50 #endif
  51
  52 static void INTERRUPT timer_irq();
  53
  54 static volatile unsigned long ticks;
  55 static unsigned long tick_interval, ticks_per_dos_intr;
  56 static int inum;
  57
  58 void init_timer(int res_hz)
  59 {
  60         _disable();
  61
  62         if(res_hz > 0) {
  63                 int reload_val = DIV_ROUND(OSC_FREQ_HZ, res_hz);
  64                 set_timer_reload(reload_val);
  65
  66                 tick_interval = DIV_ROUND(1000, res_hz);
  67                 ticks_per_dos_intr = DIV_ROUND(65535L, reload_val);
  68
  69                 inum = PIT_TIMER_INTR;
  70 #ifdef __WATCOMC__
  71                 prev_timer_intr = _dos_getvect(inum);
  72                 _dos_setvect(inum, timer_irq);
  73 #endif
  74 #ifdef __DJGPP__
  75                 _go32_dpmi_get_protected_mode_interrupt_vector(inum, &prev_intr);
  76                 intr.pm_offset = (intptr_t)timer_irq;
  77                 intr.pm_selector = _go32_my_cs();
  78                 _go32_dpmi_allocate_iret_wrapper(&intr);
  79                 _go32_dpmi_set_protected_mode_interrupt_vector(inum, &intr);
  80 #endif
  81         } else {
  82                 tick_interval = 55;
  83
  84                 inum = DOS_TIMER_INTR;
  85 #ifdef __WATCOMC__
  86                 prev_timer_intr = _dos_getvect(inum);
  87                 _dos_setvect(inum, dos_timer_intr);
  88 #endif
  89 #ifdef __DJGPP__
  90                 assert(0);
  91 #endif
  92         }
  93         _enable();
  94
  95         atexit(cleanup);
  96 }
  97
  98 static void cleanup(void)
  99 {
 100         if(!inum) {
 101                 return; /* init hasn't ran, there's nothing to cleanup */
 102         }
 103
 104         _disable();
 105         if(inum == PIT_TIMER_INTR) {
 106                 /* restore the original timer frequency */
 107                 set_timer_reload(65535);
 108         }
 109
 110         /* restore the original interrupt handler */
 111 #ifdef __WATCOMC__
 112         _dos_setvect(inum, prev_timer_intr);
 113 #endif
 114 #ifdef __DJGPP__
 115         _go32_dpmi_set_protected_mode_interrupt_vector(inum, &prev_intr);
 116         _go32_dpmi_free_iret_wrapper(&intr);
 117 #endif
 118
 119         _enable();
 120 }
 121
 122 void reset_timer(void)
 123 {
 124         ticks = 0;
 125 }
 126
 127 unsigned long get_msec(void)
 128 {
 129         return ticks * tick_interval;
 130 }
 131
 132 void sleep_msec(unsigned long msec)
 133 {
 134         unsigned long wakeup_time = ticks + msec / tick_interval;
 135         while(ticks < wakeup_time) {
 136 #ifdef USE_HLT
 137                 halt();
 138 #endif
 139         }
 140 }
 141
 142 static void set_timer_reload(int reload_val)
 143 {
 144         outp(PORT_CMD, CMD_CHAN0 | CMD_ACCESS_BOTH | CMD_OP_SQWAVE);
 145         outp(PORT_DATA0, reload_val & 0xff);
 146         outp(PORT_DATA0, (reload_val >> 8) & 0xff);
 147 }
 148
 149 #ifdef __WATCOMC__
 150 static void INTERRUPT dos_timer_intr()
 151 {
 152         ticks++;
 153         _chain_intr(prev_timer_intr);   /* DOES NOT RETURN */
 154 }
 155 #endif
 156
 157 /* first PIC command port */
 158 #define PIC1_CMD        0x20
 159 /* end of interrupt control word */
 160 #define OCW2_EOI        (1 << 5)
 161
 162 static void INTERRUPT timer_irq()
 163 {
 164         static unsigned long dos_ticks;
 165
 166         ticks++;
 167
 168 #ifdef __WATCOMC__
 169         if(++dos_ticks >= ticks_per_dos_intr) {
 170                 /* I suppose the dos irq handler does the EOI so I shouldn't
 171                  * do it if I am to call the previous function
 172                  */
 173                 dos_ticks = 0;
 174                 _chain_intr(prev_timer_intr);   /* XXX DOES NOT RETURN */
 175                 return; /* just for clarity */
 176         }
 177 #endif
 178
 179         /* send EOI to the PIC */
 180         outp(PIC1_CMD, OCW2_EOI);
 181 }
 182
 183 #endif  /* NO_SOUND */