tsc.h

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#ifndef CPU_X86_TSC_H
#define CPU_X86_TSC_H
 
#include <stdint.h>
 
#if CONFIG(TSC_SYNC_MFENCE)
#define TSC_SYNC "mfence\n"
#elif CONFIG(TSC_SYNC_LFENCE)
#define TSC_SYNC "lfence\n"
#else
#define TSC_SYNC
#endif
 
struct tsc_struct {
        unsigned int lo;
        unsigned int hi;
};
typedef struct tsc_struct tsc_t;
 
static inline tsc_t rdtsc(void)
{
        tsc_t res;
        asm volatile (
                TSC_SYNC
                "rdtsc"
                : "=a" (res.lo), "=d"(res.hi) /* outputs */
        );
        return res;
}
 
/* Simple 32- to 64-bit multiplication. Uses 16-bit words to avoid overflow.
 * This code is used to prevent use of libgcc's umoddi3.
 */
static inline void multiply_to_tsc(tsc_t *const tsc, const u32 a, const u32 b)
{
        tsc->lo = (a & 0xffff) * (b & 0xffff);
        tsc->hi = ((tsc->lo >> 16)
                + ((a & 0xffff) * (b >> 16))
                + ((b & 0xffff) * (a >> 16)));
        tsc->lo = ((tsc->hi & 0xffff) << 16) | (tsc->lo & 0xffff);
        tsc->hi = ((a >> 16) * (b >> 16)) + (tsc->hi >> 16);
}
 
static inline uint64_t tsc_to_uint64(tsc_t tstamp)
{
        return (((uint64_t)tstamp.hi) << 32) + tstamp.lo;
}
 
static inline unsigned long long rdtscll(void)
{
        return tsc_to_uint64(rdtsc());
}
 
/* Provided by CPU/chipset code for the TSC rate in MHz. */
unsigned long tsc_freq_mhz(void);
 
static inline int tsc_constant_rate(void)
{
        return !CONFIG(UNKNOWN_TSC_RATE);
}
 
#endif /* CPU_X86_TSC_H */