Kernel/arch/x86/time.c

   1 /*
   2  * Acess2 Kernel
   3  * Timekeeping
   4  * arch/x86/time.c
   5  */
   6 #include <acess.h>
   7
   8 // === MACROS ===
   9 #define TIMER_QUANTUM   100
  10 // 2^(15-rate), 15: 1HZ, 5: 1024Hz, 2: 8192Hz
  11 #define TIMER_RATE      12      // (Max: 15, Min: 2) - 15 = 1Hz, 13 = 4Hz, 12 = 8Hz, 11 = 16Hz 10 = 32Hz, 2
  12 #define TIMER_FREQ      (0x8000>>TIMER_RATE)    //Hz
  13 #define MS_PER_TICK_WHOLE       (1000/(TIMER_FREQ))
  14 #define MS_PER_TICK_FRACT       ((Uint64)(1000*TIMER_FREQ-((Uint64)MS_PER_TICK_WHOLE)*0x80000000/TIMER_FREQ))
  15
  16 // === IMPORTS ===
  17 extern Sint64   giTimestamp;
  18 extern Uint64   giTicks;
  19 extern Uint64   giPartMiliseconds;
  20 extern void     Timer_CallTimers(void);
  21
  22 // === PROTOTYPES ===
  23 void    Time_Interrupt();
  24
  25 // === CODE ===
  26 /**
  27  * \fn int Time_Setup()
  28  * \brief Sets the system time from the Realtime-Clock
  29  */
  30 int Time_Setup()
  31 {
  32         Uint8   val;
  33
  34         outb(0x70, inb(0x70)&0x7F);     // Disable NMIs
  35         __asm__ __volatile__ ("cli");   // Disable normal interrupts
  36
  37         // Set IRQ8 firing rate
  38         outb(0x70, 0x0A);       // Set the index to register A
  39         val = inb(0x71); // Get the current value of register A
  40         outb(0x70, 0x0A); // Reset index to A
  41         val &= 0xF0;
  42         val |= TIMER_RATE;
  43         outb(0x71, val);        // Update the timer rate
  44
  45         // Enable IRQ8
  46         outb(0x70, 0x0B);       // Set the index to register B
  47         val = inb(0x71);        // Read the current value of register B
  48         outb(0x70, 0x0B);       // Set the index again (a read will reset the index to register D)
  49         outb(0x71, val | 0x40); // Write the previous value or'd with 0x40. This turns on bit 6 of register D
  50
  51         __asm__ __volatile__ ("sti");   // Disable normal interrupts
  52         outb(0x70, inb(0x70)|0x80);     // Disable NMIs
  53
  54         // Install IRQ Handler
  55         IRQ_AddHandler(8, Time_Interrupt);
  56         return 0;
  57 }
  58
  59 /**
  60  * \fn void Time_Interrupt()
  61  * \brief Called on the timekeeping IRQ
  62  */
  63 void Time_Interrupt()
  64 {
  65         giTicks ++;
  66         giTimestamp += MS_PER_TICK_WHOLE;
  67         giPartMiliseconds += MS_PER_TICK_FRACT;
  68         if(giPartMiliseconds > 0x80000000) {
  69                 giTimestamp ++;
  70                 giPartMiliseconds -= 0x80000000;
  71         }
  72
  73         Timer_CallTimers();
  74
  75         // Make sure the RTC Fires again
  76         outb(0x70, 0x0C); // Select register C
  77         inb(0x71);      // Just throw away contents.
  78 }
  79
  80 #if 0
  81 /**
  82  * \fn void Time_TimerThread()
  83  */
  84 void Time_TimerThread()
  85 {
  86         Sint64  next;
  87         Threads_SetName("TIMER");
  88
  89         next = giTimestamp + TIMER_QUANTUM;
  90         for(;;)
  91         {
  92                 while(giTimestamp < next)       Threads_Yield();
  93                 next = giTimestamp + TIMER_QUANTUM;
  94                 Timer_CallTimers();
  95         }
  96 }
  97 #endif