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