grub/kern/i386/pit.c
chrfranke 5c41d44d7d 2008-08-07 Christian Franke <franke@computer.org>
* kern/i386/pit.c (TIMER2_SPEAKER): New define.
	(TIMER2_GATE): Likewise.
	(grub_pit_wait): Add enable/disable of the timer2 gate
	bit of port 0x61.  This fixes a possible infinite loop.
2008-08-07 19:43:36 +00:00

56 lines
1.8 KiB
C

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