Kernel/arch/x86_64/time.c

   1 /*
   2  * Acess2 Kernel
   3  * Timekeeping
   4  * arch/x86_64/time.c
   5  */
   6 #include <acess.h>
   7 #include <arch_config.h>
   8
   9 // === MACROS ===
  10 #define TIMER_QUANTUM   100
  11 #define TIMER_FREQ      PIT_TIMER_BASE_N/(PIT_TIMER_BASE_D*PIT_TIMER_DIVISOR)
  12 #define MS_PER_TICK_WHOLE       (1000*(PIT_TIMER_BASE_D*PIT_TIMER_DIVISOR)/PIT_TIMER_BASE_N)
  13 #define MS_PER_TICK_FRACT       ((0x80000000ULL*1000ULL*PIT_TIMER_BASE_D*PIT_TIMER_DIVISOR/PIT_TIMER_BASE_N)&0x7FFFFFFF)
  14
  15 // === IMPORTS ===
  16 extern volatile Sint64  giTimestamp;
  17 extern volatile Uint64  giTicks;
  18 extern volatile Uint64  giPartMiliseconds;
  19 extern void     Timer_CallTimers(void);
  20
  21 // === GLOBALS ===
  22 volatile Uint64 giTime_TSCAtLastTick = 0;
  23 volatile Uint64 giTime_TSCPerTick = 0;
  24
  25 // === PROTOTYPES ===
  26 //Sint64        now(void);
  27  int    Time_Setup(void);
  28 void    Time_UpdateTimestamp(void);
  29 Uint64  Time_ReadTSC(void);
  30
  31 // === CODE ===
  32 /**
  33  * \fn Sint64 now()
  34  * \brief Return the current timestamp
  35  */
  36 Sint64 now(void)
  37 {
  38         Uint64  tsc = Time_ReadTSC();
  39         tsc -= giTime_TSCAtLastTick;
  40         tsc *= MS_PER_TICK_WHOLE;
  41         if( giTime_TSCPerTick ) {
  42                 tsc /= giTime_TSCPerTick;
  43         }
  44         else
  45                 tsc = 0;
  46         return giTimestamp + tsc;
  47 }
  48
  49 /**
  50  * \fn int Time_Setup(void)
  51  * \brief Sets the system time from the Realtime-Clock
  52  */
  53 int Time_Setup(void)
  54 {
  55         Log_Log("Timer", "PIT Timer firing at %iHz, %i.0x%08x miliseconds per tick",
  56                 TIMER_FREQ, MS_PER_TICK_WHOLE, MS_PER_TICK_FRACT);
  57
  58         // TODO: Read time from RTC
  59
  60         return 0;
  61 }
  62
  63 /**
  64  * \brief Called on the timekeeping IRQ
  65  */
  66 void Time_UpdateTimestamp(void)
  67 {
  68         Uint64  curTSC = Time_ReadTSC();
  69
  70         if( giTime_TSCAtLastTick )
  71         {
  72                 giTime_TSCPerTick = curTSC - giTime_TSCAtLastTick;
  73         }
  74         giTime_TSCAtLastTick = curTSC;
  75
  76         giTicks ++;
  77         giTimestamp += MS_PER_TICK_WHOLE;
  78         giPartMiliseconds += MS_PER_TICK_FRACT;
  79         if(giPartMiliseconds > 0x80000000) {
  80                 giTimestamp ++;
  81                 giPartMiliseconds -= 0x80000000;
  82         }
  83
  84         Timer_CallTimers();
  85 }
  86
  87 #if 0
  88 /**
  89  * \fn void Time_TimerThread(void)
  90  */
  91 void Time_TimerThread(void)
  92 {
  93         Sint64  next;
  94         Threads_SetName("TIMER");
  95
  96         next = giTimestamp + TIMER_QUANTUM;
  97         for(;;)
  98         {
  99                 while(giTimestamp < next)       Threads_Yield();
 100                 next = giTimestamp + TIMER_QUANTUM;
 101                 Timer_CallTimers();
 102         }
 103 }
 104 #endif
 105
 106 Uint64 Time_ReadTSC(void)
 107 {
 108         Uint32  a, d;
 109         __asm__ __volatile__ ("rdtsc" : "=a" (a), "=d" (d));
 110         return ((Uint64)d << 32) | a;
 111 }