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79 lines
2.5 KiB
C
79 lines
2.5 KiB
C
/* kern/i386/tsc.c - x86 TSC time source implementation
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* Requires Pentium or better x86 CPU that supports the RDTSC instruction.
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* This module calibrates the TSC to real time.
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*
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* GRUB -- GRand Unified Bootloader
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* Copyright (C) 2008 Free Software Foundation, Inc.
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*
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* GRUB is free software: you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation, either version 3 of the License, or
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* (at your option) any later version.
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*
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* GRUB is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with GRUB. If not, see <http://www.gnu.org/licenses/>.
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*/
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#include <grub/types.h>
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#include <grub/time.h>
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#include <grub/misc.h>
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#include <grub/i386/tsc.h>
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#include <grub/i386/cpuid.h>
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/* This defines the value TSC had at the epoch (that is, when we calibrated it). */
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static grub_uint64_t tsc_boot_time;
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/* Calibrated TSC rate. (In ms per 2^32 ticks) */
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/* We assume that the tick is less than 1 ms and hence this value fits
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in 32-bit. */
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grub_uint32_t grub_tsc_rate;
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static grub_uint64_t
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grub_tsc_get_time_ms (void)
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{
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grub_uint64_t a = grub_get_tsc () - tsc_boot_time;
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grub_uint64_t ah = a >> 32;
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grub_uint64_t al = a & 0xffffffff;
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return ((al * grub_tsc_rate) >> 32) + ah * grub_tsc_rate;
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}
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static int
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calibrate_tsc_hardcode (void)
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{
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grub_tsc_rate = 5368;/* 800 MHz */
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return 1;
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}
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void
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grub_tsc_init (void)
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{
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if (!grub_cpu_is_tsc_supported ())
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{
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#if defined (GRUB_MACHINE_PCBIOS) || defined (GRUB_MACHINE_IEEE1275)
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grub_install_get_time_ms (grub_rtc_get_time_ms);
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#else
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grub_fatal ("no TSC found");
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#endif
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return;
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}
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tsc_boot_time = grub_get_tsc ();
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#ifdef GRUB_MACHINE_XEN
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(void) (grub_tsc_calibrate_from_xen () || calibrate_tsc_hardcode());
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#elif defined (GRUB_MACHINE_EFI)
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(void) (grub_tsc_calibrate_from_pit () || grub_tsc_calibrate_from_pmtimer () || grub_tsc_calibrate_from_efi() || calibrate_tsc_hardcode());
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#elif defined (GRUB_MACHINE_COREBOOT)
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(void) (grub_tsc_calibrate_from_pmtimer () || grub_tsc_calibrate_from_pit () || calibrate_tsc_hardcode());
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#else
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(void) (grub_tsc_calibrate_from_pit () || calibrate_tsc_hardcode());
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#endif
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grub_install_get_time_ms (grub_tsc_get_time_ms);
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}
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