1 #ifndef _GPXE_RDTSC_TIMER_H 2 #define _GPXE_RDTSC_TIMER_H 3 4 /** @file 5 * 6 * RDTSC timer 7 * 8 */ 9 10 FILE_LICENCE ( GPL2_OR_LATER ); 11 12 #ifdef TIMER_RDTSC 13 #define TIMER_PREFIX_rdtsc 14 #else 15 #define TIMER_PREFIX_rdtsc __rdtsc_ 16 #endif 17 18 /** 19 * RDTSC values can easily overflow an unsigned long. We discard the 20 * low-order bits in order to obtain sensibly-scaled values. 21 */ 22 #define TSC_SHIFT 8 23 24 /** 25 * Get current system time in ticks 26 * 27 * @ret ticks Current time, in ticks 28 */ 29 static inline __always_inline unsigned long 30 TIMER_INLINE ( rdtsc, currticks ) ( void ) { 31 unsigned long ticks; 32 33 __asm__ __volatile__ ( "rdtsc\n\t" 34 "shrdl %1, %%edx, %%eax\n\t" 35 : "=a" ( ticks ) : "i" ( TSC_SHIFT ) : "edx" ); 36 return ticks; 37 } 38 39 #endif /* _GPXE_RDTSC_TIMER_H */ 40
