89 lines
2.5 KiB
C
89 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 uses the PIT to calibrate the TSC to
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* real time.
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*
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* VasEBoot -- GRand Unified Bootloader
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* Copyright (C) 2008 Free Software Foundation, Inc.
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*
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* VasEBoot 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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* VasEBoot 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 VasEBoot. If not, see <http://www.gnu.org/licenses/>.
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*/
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#include <VasEBoot/types.h>
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#include <VasEBoot/time.h>
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#include <VasEBoot/misc.h>
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#include <VasEBoot/i386/tsc.h>
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#include <VasEBoot/i386/pmtimer.h>
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#include <VasEBoot/acpi.h>
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#include <VasEBoot/cpu/io.h>
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VasEBoot_uint64_t
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VasEBoot_pmtimer_wait_count_tsc (VasEBoot_port_t pmtimer,
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VasEBoot_uint16_t num_pm_ticks)
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{
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VasEBoot_uint32_t start;
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VasEBoot_uint32_t last;
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VasEBoot_uint32_t cur, end;
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VasEBoot_uint64_t start_tsc;
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VasEBoot_uint64_t end_tsc;
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int num_iter = 0;
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start = VasEBoot_inl (pmtimer) & 0xffffff;
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last = start;
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end = start + num_pm_ticks;
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start_tsc = VasEBoot_get_tsc ();
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while (1)
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{
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cur = VasEBoot_inl (pmtimer) & 0xffffff;
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if (cur < last)
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cur |= 0x1000000;
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num_iter++;
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if (cur >= end)
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{
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end_tsc = VasEBoot_get_tsc ();
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return end_tsc - start_tsc;
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}
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/* Check for broken PM timer.
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50000000 TSCs is between 5 ms (10GHz) and 200 ms (250 MHz)
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if after this time we still don't have 1 ms on pmtimer, then
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pmtimer is broken.
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*/
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if ((num_iter & 0xffffff) == 0 && VasEBoot_get_tsc () - start_tsc > 5000000) {
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return 0;
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}
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}
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}
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int
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VasEBoot_tsc_calibrate_from_pmtimer (void)
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{
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struct VasEBoot_acpi_fadt *fadt;
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VasEBoot_port_t pmtimer;
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VasEBoot_uint64_t tsc_diff;
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fadt = VasEBoot_acpi_find_fadt ();
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if (!fadt)
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return 0;
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pmtimer = fadt->pmtimer;
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if (!pmtimer)
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return 0;
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/* It's 3.579545 MHz clock. Wait 1 ms. */
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tsc_diff = VasEBoot_pmtimer_wait_count_tsc (pmtimer, 3580);
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if (tsc_diff == 0)
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return 0;
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VasEBoot_tsc_rate = VasEBoot_divmod64 ((1ULL << 32), tsc_diff, 0);
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return 1;
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}
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