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 // (Max: 15, Min: 2) - 15 = 1Hz, 13 = 4Hz, 12 = 8Hz, 11 = 16Hz 10 = 32Hz, 2 = 8192Hz
  12 //#define TIMER_RATE    10      // 32 Hz
  13 //#define TIMER_RATE    12      // 8 Hz
  14 #define TIMER_RATE      14      // 2Hz
  15 //#define TIMER_RATE    15      // 1HZ
  16 #define TIMER_FREQ      (0x8000>>TIMER_RATE)    //Hz
  17 #define MS_PER_TICK_WHOLE       (1000/(TIMER_FREQ))
  18 #define MS_PER_TICK_FRACT       ((0x80000000*(1000%TIMER_FREQ))/TIMER_FREQ)
  19
  20 // === IMPORTS ===
  21 extern volatile Sint64  giTimestamp;
  22 extern volatile Uint64  giTicks;
  23 extern volatile Uint64  giPartMiliseconds;
  24 extern void     Timer_CallTimers(void);
  25
  26 // === GLOBALS ===
  27 volatile Uint64 giTime_TSCAtLastTick = 0;
  28 volatile Uint64 giTime_TSCPerTick = 0;
  29
  30 // === PROTOTYPES ===
  31 Sint64  now(void);
  32  int    Time_Setup(void);
  33 void    Time_Interrupt(int);
  34 Uint64  Time_ReadTSC(void);
  35
  36 // === CODE ===
  37 /**
  38  * \fn Sint64 now()
  39  * \brief Return the current timestamp
  40  */
  41 Sint64 now(void)
  42 {
  43         Uint64  tsc = Time_ReadTSC();
  44         tsc -= giTime_TSCAtLastTick;
  45         tsc *= MS_PER_TICK_WHOLE;
  46         if( giTime_TSCPerTick ) {
  47                 tsc /= giTime_TSCPerTick;
  48         }
  49         else
  50                 tsc = 0;
  51         return giTimestamp + tsc;
  52 }
  53
  54 /**
  55  * \fn int Time_Setup(void)
  56  * \brief Sets the system time from the Realtime-Clock
  57  */
  58 int Time_Setup(void)
  59 {
  60         Uint8   val;
  61
  62         Log_Log("Timer", "RTC Timer firing at %iHz (%i divisor), %i.0x%08x",
  63                 TIMER_FREQ, TIMER_RATE, MS_PER_TICK_WHOLE, MS_PER_TICK_FRACT);
  64
  65         outb(0x70, inb(0x70)&0x7F);     // Disable NMIs
  66         __asm__ __volatile__ ("cli");   // Disable normal interrupts
  67
  68         // Set IRQ8 firing rate
  69         outb(0x70, 0x0A);       // Set the index to register A
  70         val = inb(0x71); // Get the current value of register A
  71         outb(0x70, 0x0A); // Reset index to A
  72         val &= 0xF0;
  73         val |= TIMER_RATE;
  74         outb(0x71, val);        // Update the timer rate
  75
  76         // Enable IRQ8
  77         outb(0x70, 0x0B);       // Set the index to register B
  78         val = inb(0x71);        // Read the current value of register B
  79         outb(0x70, 0x0B);       // Set the index again (a read will reset the index to register D)
  80         outb(0x71, val | 0x40); // Write the previous value or'd with 0x40. This turns on bit 6 of register D
  81
  82         __asm__ __volatile__ ("sti");   // Re-enable normal interrupts
  83         outb(0x70, inb(0x70)|0x80);     // Re-enable NMIs
  84
  85         // Install IRQ Handler
  86         IRQ_AddHandler(8, Time_Interrupt);
  87
  88         // Make sure the RTC actually fires
  89         outb(0x70, 0x0C); // Select register C
  90         inb(0x71);      // Just throw away contents.
  91
  92         return 0;
  93 }
  94
  95 /**
  96  * \brief Called on the timekeeping IRQ
  97  * \param irq   IRQ number (unused)
  98  */
  99 void Time_Interrupt(int irq)
 100 {
 101         //Log("RTC Tick");
 102         Uint64  curTSC = Time_ReadTSC();
 103
 104         if( giTime_TSCAtLastTick )
 105         {
 106                 giTime_TSCPerTick = curTSC - giTime_TSCAtLastTick;
 107                 //Log("curTSC = %lli, giTime_TSCPerTick = %lli", curTSC, giTime_TSCPerTick);
 108         }
 109         giTime_TSCAtLastTick = curTSC;
 110
 111         giTicks ++;
 112         giTimestamp += MS_PER_TICK_WHOLE;
 113         giPartMiliseconds += MS_PER_TICK_FRACT;
 114         if(giPartMiliseconds > 0x80000000) {
 115                 giTimestamp ++;
 116                 giPartMiliseconds -= 0x80000000;
 117         }
 118
 119         Timer_CallTimers();
 120
 121         // Make sure the RTC Fires again
 122         outb(0x70, 0x0C); // Select register C
 123         inb(0x71);      // Just throw away contents.
 124 }
 125
 126 #if 0
 127 /**
 128  * \fn void Time_TimerThread(void)
 129  */
 130 void Time_TimerThread(void)
 131 {
 132         Sint64  next;
 133         Threads_SetName("TIMER");
 134
 135         next = giTimestamp + TIMER_QUANTUM;
 136         for(;;)
 137         {
 138                 while(giTimestamp < next)       Threads_Yield();
 139                 next = giTimestamp + TIMER_QUANTUM;
 140                 Timer_CallTimers();
 141         }
 142 }
 143 #endif
 144
 145 Uint64 Time_ReadTSC(void)
 146 {
 147         Uint32  a, d;
 148         __asm__ __volatile__ ("rdtsc" : "=a" (a), "=d" (d));
 149         return ((Uint64)d << 32) | a;
 150 }