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Urgh, and now actually add the files :-)

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marco_g 2008-08-05 12:26:29 +00:00
parent 9c2ff3eefe
commit a829251bdb
10 changed files with 386 additions and 24 deletions
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102
kern/i386/tsc.c Normal file
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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 RTC (via grub_get_rtc()) 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>
/* Calibrated reference for TSC=0. This defines the time since the epoch in
milliseconds that TSC=0 refers to. */
static grub_uint64_t tsc_boot_time;
/* Calibrated TSC rate. (In TSC ticks per millisecond.) */
static grub_uint64_t tsc_ticks_per_ms;
grub_uint64_t
grub_tsc_get_time_ms (void)
{
return tsc_boot_time + grub_divmod64 (grub_get_tsc (), tsc_ticks_per_ms, 0);
}
/* How many RTC ticks to use for calibration loop. (>= 1) */
#define CALIBRATION_TICKS 2
/* Calibrate the TSC based on the RTC. */
static void
calibrate_tsc (void)
{
/* First calbrate the TSC rate (relative, not absolute time). */
grub_uint64_t start_tsc;
grub_uint64_t end_tsc;
grub_uint32_t initial_tick;
grub_uint32_t start_tick;
grub_uint32_t end_tick;
/* Wait for the start of the next tick;
we'll base out timing off this edge. */
initial_tick = grub_get_rtc ();
do
{
start_tick = grub_get_rtc ();
}
while (start_tick == initial_tick);
start_tsc = grub_get_tsc ();
/* Wait for the start of the next tick. This will
be the end of the 1-tick period. */
do
{
end_tick = grub_get_rtc ();
}
while (end_tick - start_tick < CALIBRATION_TICKS);
end_tsc = grub_get_tsc ();
tsc_ticks_per_ms =
grub_divmod64 (grub_divmod64
(end_tsc - start_tsc, end_tick - start_tick, 0)
* GRUB_TICKS_PER_SECOND, 1000, 0);
/* Reference the TSC zero (boot time) to the epoch to
get an absolute real time reference. */
grub_uint64_t ms_since_boot = grub_divmod64 (end_tsc, tsc_ticks_per_ms, 0);
grub_uint64_t mstime_now = grub_divmod64 ((grub_uint64_t) 1000 * end_tick,
GRUB_TICKS_PER_SECOND,
0);
tsc_boot_time = mstime_now - ms_since_boot;
}
void
grub_tsc_init (void)
{
if (grub_cpu_is_tsc_supported ())
{
calibrate_tsc ();
grub_install_get_time_ms (grub_tsc_get_time_ms);
}
else
{
grub_install_get_time_ms (grub_rtc_get_time_ms);
}
}