kern

annotate src/timer.c @ 35:06172322fb76

- made interrupt number - irq mapping macros public in intr.h - disabled the interrupts in various vga driver functions
author John Tsiombikas <nuclear@member.fsf.org>
date Thu, 09 Jun 2011 05:09:49 +0300
parents 17433fcaa563
children 2c401f69128e
rev   line source
nuclear@33 1 #include <stdio.h>
nuclear@33 2 #include "intr.h"
nuclear@33 3 #include "asmops.h"
nuclear@34 4 #include "timer.h"
nuclear@33 5 #include "config.h"
nuclear@33 6
nuclear@33 7 /* frequency of the oscillator driving the 8254 timer */
nuclear@33 8 #define OSC_FREQ_HZ 1193182
nuclear@33 9
nuclear@33 10 /* macro to divide and round to the nearest integer */
nuclear@33 11 #define DIV_ROUND(a, b) ((a) / (b) + ((a) % (b)) / ((b) / 2))
nuclear@33 12
nuclear@33 13 /* I/O ports connected to the 8254 */
nuclear@33 14 #define PORT_DATA0 0x40
nuclear@33 15 #define PORT_DATA1 0x41
nuclear@33 16 #define PORT_DATA2 0x42
nuclear@33 17 #define PORT_CMD 0x43
nuclear@33 18
nuclear@33 19 /* command bits */
nuclear@33 20 #define CMD_CHAN0 0
nuclear@33 21 #define CMD_CHAN1 (1 << 6)
nuclear@33 22 #define CMD_CHAN2 (2 << 6)
nuclear@33 23 #define CMD_RDBACK (3 << 6)
nuclear@33 24
nuclear@33 25 #define CMD_LATCH 0
nuclear@33 26 #define CMD_ACCESS_LOW (1 << 4)
nuclear@33 27 #define CMD_ACCESS_HIGH (2 << 4)
nuclear@33 28 #define CMD_ACCESS_BOTH (3 << 4)
nuclear@33 29
nuclear@33 30 #define CMD_OP_INT_TERM 0
nuclear@33 31 #define CMD_OP_ONESHOT (1 << 1)
nuclear@33 32 #define CMD_OP_RATE (2 << 1)
nuclear@33 33 #define CMD_OP_SQWAVE (3 << 1)
nuclear@33 34 #define CMD_OP_SOFT_STROBE (4 << 1)
nuclear@33 35 #define CMD_OP_HW_STROBE (5 << 1)
nuclear@33 36
nuclear@33 37 #define CMD_MODE_BIN 0
nuclear@33 38 #define CMD_MODE_BCD 1
nuclear@33 39
nuclear@33 40
nuclear@33 41 static void intr_handler();
nuclear@33 42
nuclear@33 43
nuclear@33 44 void init_timer(void)
nuclear@33 45 {
nuclear@34 46 /* calculate the reload count: round(osc / freq) */
nuclear@34 47 int reload_count = DIV_ROUND(OSC_FREQ_HZ, TICK_FREQ_HZ);
nuclear@33 48
nuclear@33 49 /* set the mode to square wave for channel 0, both low
nuclear@34 50 * and high reload count bytes will follow...
nuclear@33 51 */
nuclear@33 52 outb(CMD_CHAN0 | CMD_ACCESS_BOTH | CMD_OP_SQWAVE, PORT_CMD);
nuclear@33 53
nuclear@34 54 /* write the low and high bytes of the reload count to the
nuclear@33 55 * port for channel 0
nuclear@33 56 */
nuclear@34 57 outb(reload_count & 0xff, PORT_DATA0);
nuclear@34 58 outb((reload_count >> 8) & 0xff, PORT_DATA0);
nuclear@33 59
nuclear@33 60 /* set the timer interrupt handler */
nuclear@35 61 interrupt(IRQ_TO_INTR(0), intr_handler);
nuclear@33 62 }
nuclear@33 63
nuclear@33 64 /* This will be called by the interrupt dispatcher approximately
nuclear@33 65 * every 1/250th of a second, so it must be extremely fast.
nuclear@33 66 * For now, just increasing a tick counter will suffice.
nuclear@33 67 */
nuclear@33 68 static void intr_handler()
nuclear@33 69 {
nuclear@33 70 nticks++;
nuclear@33 71
nuclear@33 72 if(nticks % TICK_FREQ_HZ == 0) {
nuclear@33 73 printf("%lu sec\n", nticks / TICK_FREQ_HZ);
nuclear@33 74 }
nuclear@33 75 }