timebase.c

#define SPRN_TBRL       0x10C       // Time Base Read Lower Register (user & sup R/O)
#define SPRN_TBRU       0x10D       // Time Base Read Upper Register (user & sup R/O)

#define _bgp_mfspr( SPRN )\
({\
   unsigned int tmp;\
   do {\
      asm volatile ("mfspr %0,%1" : "=&r" (tmp) : "i" (SPRN) : "memory" );\
      }\
      while(0);\
   tmp;\
})\

unsigned long long timebase( void )
{
   union {
         unsigned int ul[2];
         unsigned long long  ull;
         }
         hack;
   unsigned int utmp;

   do {
      utmp       = _bgp_mfspr( SPRN_TBRU );
      hack.ul[1] = _bgp_mfspr( SPRN_TBRL );
      hack.ul[0] = _bgp_mfspr( SPRN_TBRU );
      }
      while( utmp != hack.ul[0] );

   return( hack.ull );
}

double getTime( void )
{
   union {
         unsigned int ul[2];
         unsigned long long  ull;
         }
         hack;
   unsigned int utmp;

   do {
      utmp       = _bgp_mfspr( SPRN_TBRU );
      hack.ul[1] = _bgp_mfspr( SPRN_TBRL );
      hack.ul[0] = _bgp_mfspr( SPRN_TBRU );
      }
      while( utmp != hack.ul[0] );

   return( (1.0/850000000.0) * ((double) hack.ull)  );
}