diff options
Diffstat (limited to 'lib_i386/pcat_timer.c')
-rw-r--r-- | lib_i386/pcat_timer.c | 102 |
1 files changed, 102 insertions, 0 deletions
diff --git a/lib_i386/pcat_timer.c b/lib_i386/pcat_timer.c new file mode 100644 index 0000000000..e282f649ac --- /dev/null +++ b/lib_i386/pcat_timer.c @@ -0,0 +1,102 @@ +/* + * (C) Copyright 2002 + * Daniel Engström, Omicron Ceti AB, daniel@omicron.se. + * + * See file CREDITS for list of people who contributed to this + * project. + * + * This program 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 2 of + * the License, or (at your option) any later version. + * + * This program 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 this program; if not, write to the Free Software + * Foundation, Inc., 59 Temple Place, Suite 330, Boston, + * MA 02111-1307 USA + */ + +#include <common.h> +#include <asm/io.h> +#include <asm/i8254.h> +#include <asm/ibmpc.h> + +#define TIMER0_VALUE 0x04aa /* 1kHz 1.9318MHz / 1000 */ +#define TIMER2_VALUE 0x0a8e /* 440Hz */ + +int timer_init(void) +{ + /* initialize timer 0 and 2 + * + * Timer 0 is used to increment system_tick 1000 times/sec + * Timer 1 was used for DRAM refresh in early PC's + * Timer 2 is used to drive the speaker + * (to stasrt a beep: write 3 to port 0x61, + * to stop it again: write 0) + */ + outb (PIT_CMD_CTR0 | PIT_CMD_BOTH | PIT_CMD_MODE2, + PIT_BASE + PIT_COMMAND); + outb (TIMER0_VALUE & 0xff, PIT_BASE + PIT_T0); + outb (TIMER0_VALUE >> 8, PIT_BASE + PIT_T0); + + outb (PIT_CMD_CTR2 | PIT_CMD_BOTH | PIT_CMD_MODE3, + PIT_BASE + PIT_COMMAND); + outb (TIMER2_VALUE & 0xff, PIT_BASE + PIT_T2); + outb (TIMER2_VALUE >> 8, PIT_BASE + PIT_T2); + + irq_install_handler (0, timer_isr, NULL); + unmask_irq (0); + + return 0; +} + +static u16 read_pit(void) +{ + u8 low; + + outb (PIT_CMD_LATCH, PIT_BASE + PIT_COMMAND); + low = inb (PIT_BASE + PIT_T0); + + return ((inb (PIT_BASE + PIT_T0) << 8) | low); +} + +/* this is not very exact */ +void udelay (unsigned long usec) +{ + int counter; + int wraps; + + if (timer_init_done) + { + counter = read_pit (); + wraps = usec / 1000; + usec = usec % 1000; + + usec *= 1194; + usec /= 1000; + usec += counter; + + while (usec > 1194) { + usec -= 1194; + wraps++; + } + + while (1) { + int new_count = read_pit (); + + if (((new_count < usec) && !wraps) || wraps < 0) + break; + + if (new_count > counter) + wraps--; + + counter = new_count; + } + } + +} |