OSDev

#include <cpu.h>#include <systime.h>#include <sysdata.h>#include <lock.h>

/************************************************
 tacts=(1<<32)*time

  tact - tsc
  time - length of tacts

     1 tact = (1<<32) * time_per_tact

      time_per_tact = 1 sec / frequency

 1 tact = (1<<32) * 1 sec / frequency

      1 sec =1 000 000 usec

     1 sec / frequency = 1 000 000 usec / frequency = 50 000 usec / (frequency/20) 

   1 tact = (1<<32)*50 000 usec /(frequency/20)

      time[i+1] = (tacts[i]*(1 tact)+utacts[i])/(1<<32)
  utacts[i+1] = (tacts[i]*(1 tact)+utacts[i])%(1<<32)
       
************************************************/

static unsigned __int64 tsc_delta()
{
      __int64 tsc=sys_tsc;
       sys_tsc=cpu_read_tsc();
        return sys_tsc-tsc;
}

static SYSTEM_TIME tsc_to_time(unsigned __int64 tsc)
{
      SYSTEM_TIME time=0UL;
      unsigned factor=sys_factor;
        static unsigned __int64 utsc=0UL;
  tsc=tsc*factor+utsc;
       time=tsc/0x100000000UL;
        utsc=tsc%0x100000000UL;
        return time;
}
#define time_lock() lock_lock(&sys_timelock)#define time_unlock() lock_unlock(&sys_timelock);

// run only in interrupt disabled mode
SYSTEM_TIME time_update()
{
   time_lock();
   sys_time+=tsc_to_time(tsc_delta());
    time_unlock();
 return sys_time;       
}

SYSTEM_TIME time_get_time(unsigned *low, unsigned *hi)
{
       SYSTEM_TIME time;
  time_lock();
   time=sys_time+sys_start_time;
  time_unlock();
 if (low&&hi)
   {
  *low=((unsigned*)&time)[0];
  *hi=((unsigned*)&time)[1];
       }
  return time;
}

SYSTEM_TIME time_get_uptime(unsigned *low, unsigned *hi)
{
 SYSTEM_TIME time;
  time_lock();
   time=sys_time;
 time_unlock();
 if (low&&hi)
   {
  *low=((unsigned*)&time)[0];
  *hi=((unsigned*)&time)[1];
       }
  return time;
}

  tacts=(1<<32)*time (1)

      tact - tsc
      time - length of tacts

1 tact = (1<<32) * time_per_tact (2)

time_per_tact = 1 sec / frequency (3)

1 tact = (1<<32) * 1 sec / frequency (4)