KernelLand/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 #include <timers.h>
   9
  10 // === MACROS ===
  11 #define TIMER_QUANTUM   100
  12 #define TIMER_FREQ      PIT_TIMER_BASE_N/(PIT_TIMER_BASE_D*PIT_TIMER_DIVISOR)
  13 #define MS_PER_TICK_WHOLE       (1000*(PIT_TIMER_BASE_D*PIT_TIMER_DIVISOR)/PIT_TIMER_BASE_N)
  14 #define MS_PER_TICK_FRACT       ((0x80000000ULL*1000ULL*PIT_TIMER_BASE_D*PIT_TIMER_DIVISOR/PIT_TIMER_BASE_N)&0x7FFFFFFF)
  15 #define US_PER_TICK     (1000*1000/(TIMER_FREQ))
  16
  17 // === IMPORTS ===
  18 extern volatile Sint64  giTimestamp;
  19 extern volatile Uint64  giTicks;
  20 extern volatile Uint64  giPartMiliseconds;
  21 extern void     Timer_CallTimers(void);
  22
  23 // === GLOBALS ===
  24 volatile Uint64 giTime_TSCAtLastTick = 0;
  25 volatile Uint64 giTime_TSCPerTick = 0;
  26
  27 // === PROTOTYPES ===
  28 //Sint64        now(void);
  29  int    Time_Setup(void);
  30 void    Time_UpdateTimestamp(void);
  31 Uint64  Time_ReadTSC(void);
  32
  33 // === CODE ===
  34 /**
  35  * \fn Sint64 now()
  36  * \brief Return the current timestamp
  37  */
  38 Sint64 now(void)
  39 {
  40         Uint64  tsc = Time_ReadTSC();
  41         tsc -= giTime_TSCAtLastTick;
  42         tsc *= MS_PER_TICK_WHOLE;
  43         if( giTime_TSCPerTick ) {
  44                 tsc /= giTime_TSCPerTick;
  45         }
  46         else
  47                 tsc = 0;
  48         return giTimestamp + tsc;
  49 }
  50
  51 /**
  52  * \fn int Time_Setup(void)
  53  * \brief Sets the system time from the Realtime-Clock
  54  */
  55 int Time_Setup(void)
  56 {
  57         Log_Log("Timer", "PIT Timer firing at %iHz, %i.0x%08x miliseconds per tick",
  58                 TIMER_FREQ, MS_PER_TICK_WHOLE, MS_PER_TICK_FRACT);
  59
  60         // TODO: Read time from RTC
  61
  62         return 0;
  63 }
  64
  65 /**
  66  * \brief Called on the timekeeping IRQ
  67  */
  68 void Time_UpdateTimestamp(void)
  69 {
  70         Uint64  curTSC = Time_ReadTSC();
  71
  72         if( giTime_TSCAtLastTick )
  73         {
  74                 giTime_TSCPerTick = curTSC - giTime_TSCAtLastTick;
  75         }
  76         giTime_TSCAtLastTick = curTSC;
  77
  78         giTicks ++;
  79         giTimestamp += MS_PER_TICK_WHOLE;
  80         giPartMiliseconds += MS_PER_TICK_FRACT;
  81         if(giPartMiliseconds > 0x80000000) {
  82                 giTimestamp ++;
  83                 giPartMiliseconds -= 0x80000000;
  84         }
  85
  86         Timer_CallTimers();
  87 }
  88
  89 #if 0
  90 /**
  91  * \fn void Time_TimerThread(void)
  92  */
  93 void Time_TimerThread(void)
  94 {
  95         Sint64  next;
  96         Threads_SetName("TIMER");
  97
  98         next = giTimestamp + TIMER_QUANTUM;
  99         for(;;)
 100         {
 101                 while(giTimestamp < next)       Threads_Yield();
 102                 next = giTimestamp + TIMER_QUANTUM;
 103                 Timer_CallTimers();
 104         }
 105 }
 106 #endif
 107
 108 void Time_MicroSleep(Uint16 Microsecs)  // max 64 ms
 109 {
 110         Uint64  cur_tsc = Time_ReadTSC();
 111         // tsc_per_us * Microsec
 112         Uint64  delta_tsc = (Uint64)Microsecs * giTime_TSCPerTick / US_PER_TICK;
 113         Uint64  tgt_tsc = cur_tsc + delta_tsc;
 114
 115         if( tgt_tsc < cur_tsc )
 116                 while(Time_ReadTSC() > cur_tsc)
 117                         ;
 118
 119         while( Time_ReadTSC() < tgt_tsc )
 120                 ;
 121 }
 122
 123 Uint64 Time_ReadTSC(void)
 124 {
 125         Uint32  a, d;
 126         __asm__ __volatile__ ("rdtsc" : "=a" (a), "=d" (d));
 127         return ((Uint64)d << 32) | a;
 128 }