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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 uses the PIT to calibrate 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/xen.h>
int
grub_tsc_calibrate_from_xen (void)
{
grub_uint64_t t;
t = grub_xen_shared_info->vcpu_info[0].time.tsc_to_system_mul;
if (grub_xen_shared_info->vcpu_info[0].time.tsc_shift > 0)
t <<= grub_xen_shared_info->vcpu_info[0].time.tsc_shift;
else
t >>= -grub_xen_shared_info->vcpu_info[0].time.tsc_shift;
grub_tsc_rate = grub_divmod64 (t, 1000000, 0);
return 1;
}
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