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

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