d43a5ee651
PIT isn't available on some of new hardware including Hyper-V. So use pmtimer for calibration. Moreover pmtimer calibration is faster, so use it on coreboor where booting time is important. Based on patch by Michael Chang.
40 lines
1.4 KiB
C
40 lines
1.4 KiB
C
/* 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;
|
|
}
|