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/* kern/i386/tsc.c - x86 TSC time source implementation
* Requires Pentium or better x86 CPU that supports the RDTSC instruction.
* This module calibrates the TSC to real time.
*
* GRUB -- GRand Unified Bootloader
* Copyright (C) 2008 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/>.
*/
#include <grub/types.h>
#include <grub/time.h>
#include <grub/misc.h>
#include <grub/i386/tsc.h>
#include <grub/i386/cpuid.h>
/* This defines the value TSC had at the epoch (that is, when we calibrated it). */
static grub_uint64_t tsc_boot_time;
/* Calibrated TSC rate. (In ms per 2^32 ticks) */
/* We assume that the tick is less than 1 ms and hence this value fits
in 32-bit. */
grub_uint32_t grub_tsc_rate;
static grub_uint64_t
grub_tsc_get_time_ms (void)
{
grub_uint64_t a = grub_get_tsc () - tsc_boot_time;
grub_uint64_t ah = a >> 32;
grub_uint64_t al = a & 0xffffffff;
return ((al * grub_tsc_rate) >> 32) + ah * grub_tsc_rate;
}
static int
calibrate_tsc_hardcode (void)
{
grub_tsc_rate = 5368;/* 800 MHz */
return 1;
}
void
grub_tsc_init (void)
{
if (!grub_cpu_is_tsc_supported ())
{
#if defined (GRUB_MACHINE_PCBIOS) || defined (GRUB_MACHINE_IEEE1275)
grub_install_get_time_ms (grub_rtc_get_time_ms);
#else
grub_fatal ("no TSC found");
#endif
return;
}
tsc_boot_time = grub_get_tsc ();
#if defined (GRUB_MACHINE_XEN) || defined (GRUB_MACHINE_XEN_PVH)
(void) (grub_tsc_calibrate_from_xen () || calibrate_tsc_hardcode());
#elif defined (GRUB_MACHINE_EFI)
(void) (grub_tsc_calibrate_from_pmtimer () || grub_tsc_calibrate_from_pit () || grub_tsc_calibrate_from_efi() || calibrate_tsc_hardcode());
#elif defined (GRUB_MACHINE_COREBOOT)
(void) (grub_tsc_calibrate_from_pmtimer () || grub_tsc_calibrate_from_pit () || calibrate_tsc_hardcode());
#else
(void) (grub_tsc_calibrate_from_pit () || calibrate_tsc_hardcode());
#endif
grub_install_get_time_ms (grub_tsc_get_time_ms);
}
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