56 lines
1.8 KiB
C
56 lines
1.8 KiB
C
/*
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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/i386/io.h>
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#include <grub/i386/pit.h>
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#define TIMER2_REG_CONTROL 0x42
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#define TIMER_REG_COMMAND 0x43
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#define TIMER2_REG_LATCH 0x61
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#define TIMER2_SELECT 0x80
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#define TIMER_ENABLE_LSB 0x20
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#define TIMER_ENABLE_MSB 0x10
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#define TIMER2_LATCH 0x20
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#define TIMER2_SPEAKER 0x02
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#define TIMER2_GATE 0x01
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void
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grub_pit_wait (grub_uint16_t tics)
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{
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/* Disable timer2 gate and speaker. */
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grub_outb (grub_inb (TIMER2_REG_LATCH) & ~ (TIMER2_SPEAKER | TIMER2_GATE),
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TIMER2_REG_LATCH);
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/* Set tics. */
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grub_outb (TIMER2_SELECT | TIMER_ENABLE_LSB | TIMER_ENABLE_MSB, TIMER_REG_COMMAND);
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grub_outb (tics & 0xff, TIMER2_REG_CONTROL);
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grub_outb (tics >> 8, TIMER2_REG_CONTROL);
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/* Enable timer2 gate, keep speaker disabled. */
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grub_outb ((grub_inb (TIMER2_REG_LATCH) & ~ TIMER2_SPEAKER) | TIMER2_GATE,
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TIMER2_REG_LATCH);
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/* Wait. */
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while ((grub_inb (TIMER2_REG_LATCH) & TIMER2_LATCH) == 0x00);
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/* Disable timer2 gate and speaker. */
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grub_outb (grub_inb (TIMER2_REG_LATCH) & ~ (TIMER2_SPEAKER | TIMER2_GATE),
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TIMER2_REG_LATCH);
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}
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