88 lines
2.4 KiB
C
88 lines
2.4 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/i386/pmtimer.h>
|
|
#include <grub/acpi.h>
|
|
#include <grub/cpu/io.h>
|
|
|
|
grub_uint64_t
|
|
grub_pmtimer_wait_count_tsc (grub_port_t pmtimer,
|
|
grub_uint16_t num_pm_ticks)
|
|
{
|
|
grub_uint32_t start;
|
|
grub_uint32_t last;
|
|
grub_uint32_t cur, end;
|
|
grub_uint64_t start_tsc;
|
|
grub_uint64_t end_tsc;
|
|
int num_iter = 0;
|
|
|
|
start = grub_inl (pmtimer) & 0xffffff;
|
|
last = start;
|
|
end = start + num_pm_ticks;
|
|
start_tsc = grub_get_tsc ();
|
|
while (1)
|
|
{
|
|
cur = grub_inl (pmtimer) & 0xffffff;
|
|
if (cur < last)
|
|
cur |= 0x1000000;
|
|
num_iter++;
|
|
if (cur >= end)
|
|
{
|
|
end_tsc = grub_get_tsc ();
|
|
return end_tsc - start_tsc;
|
|
}
|
|
/* Check for broken PM timer.
|
|
50000000 TSCs is between 5 ms (10GHz) and 200 ms (250 MHz)
|
|
if after this time we still don't have 1 ms on pmtimer, then
|
|
pmtimer is broken.
|
|
*/
|
|
if ((num_iter & 0xffffff) == 0 && grub_get_tsc () - start_tsc > 5000000) {
|
|
return 0;
|
|
}
|
|
}
|
|
}
|
|
|
|
int
|
|
grub_tsc_calibrate_from_pmtimer (void)
|
|
{
|
|
struct grub_acpi_fadt *fadt;
|
|
grub_port_t pmtimer;
|
|
grub_uint64_t tsc_diff;
|
|
|
|
fadt = grub_acpi_find_fadt ();
|
|
if (!fadt)
|
|
return 0;
|
|
pmtimer = fadt->pmtimer;
|
|
if (!pmtimer)
|
|
return 0;
|
|
|
|
/* It's 3.579545 MHz clock. Wait 1 ms. */
|
|
tsc_diff = grub_pmtimer_wait_count_tsc (pmtimer, 3580);
|
|
if (tsc_diff == 0)
|
|
return 0;
|
|
grub_tsc_rate = grub_divmod64 ((1ULL << 32), tsc_diff, 0);
|
|
return 1;
|
|
}
|