grub-savannah-mirror/include/grub/i386/tsc.h

/*
 *  GRUB  --  GRand Unified Bootloader
 *  Copyright (C) 2008,2009  Free Software Foundation, Inc.
 *
 *  GRUB is free software: you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License as published by
 *  the Free Software Foundation, either version 3 of the License, or
 *  (at your option) any later version.
 *
 *  GRUB is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with GRUB.  If not, see <http://www.gnu.org/licenses/>.
 */

#ifndef KERNEL_CPU_TSC_HEADER
#define KERNEL_CPU_TSC_HEADER   1

#include <grub/types.h>
#include <grub/i386/cpuid.h>

void grub_tsc_init (void);
/* In ms per 2^32 ticks.  */
extern grub_uint32_t EXPORT_VAR(grub_tsc_rate);
int
grub_tsc_calibrate_from_xen (void);
int
grub_tsc_calibrate_from_efi (void);
int
grub_tsc_calibrate_from_pmtimer (void);
int
grub_tsc_calibrate_from_pit (void);

/* Read the TSC value, which increments with each CPU clock cycle. */
static __inline grub_uint64_t
grub_get_tsc (void)
{
  grub_uint32_t lo, hi;
  grub_uint32_t a,b,c,d;

  /* The CPUID instruction is a 'serializing' instruction, and
     avoids out-of-order execution of the RDTSC instruction. */
  grub_cpuid (0,a,b,c,d);
  /* Read TSC value.  We cannot use "=A", since this would use
     %rax on x86_64. */
  asm volatile ("rdtsc":"=a" (lo), "=d" (hi));
  /*
   * Run cpuid after rdtsc instruction to ensure rdtsc is executed before
   * subsequent instruction.
   */
  grub_cpuid (0, a, b, c, d);

  return (((grub_uint64_t) hi) << 32) | lo;
}

static __inline int
grub_cpu_is_tsc_supported (void)
{
#if !defined(GRUB_MACHINE_XEN) && !defined(GRUB_MACHINE_XEN_PVH)
  grub_uint32_t a,b,c,d;
  if (! grub_cpu_is_cpuid_supported ())
    return 0;

  grub_cpuid(1,a,b,c,d);

  return (d & (1 << 4)) != 0;
#else
  return 1;
#endif
}

#endif /* ! KERNEL_CPU_TSC_HEADER */