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annotate src/timer.c @ 55:88a6c4e192f9

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Fixed most important task switching bugs. Now it seems that I can switch in and out of user space reliably.
author John Tsiombikas <nuclear@member.fsf.org>
date Mon, 15 Aug 2011 04:03:39 +0300
parents b1e8c8251884
children 0be4615594df
rev   line source
nuclear@33 1 #include <stdio.h>
nuclear@37 2 #include <time.h>
nuclear@33 3 #include "intr.h"
nuclear@33 4 #include "asmops.h"
nuclear@34 5 #include "timer.h"
nuclear@51 6 #include "proc.h"
nuclear@51 7 #include "sched.h"
nuclear@33 8 #include "config.h"
nuclear@33 9
nuclear@33 10 /* frequency of the oscillator driving the 8254 timer */
nuclear@33 11 #define OSC_FREQ_HZ 1193182
nuclear@33 12
nuclear@33 13 /* macro to divide and round to the nearest integer */
nuclear@33 14 #define DIV_ROUND(a, b) ((a) / (b) + ((a) % (b)) / ((b) / 2))
nuclear@33 15
nuclear@33 16 /* I/O ports connected to the 8254 */
nuclear@33 17 #define PORT_DATA0 0x40
nuclear@33 18 #define PORT_DATA1 0x41
nuclear@33 19 #define PORT_DATA2 0x42
nuclear@33 20 #define PORT_CMD 0x43
nuclear@33 21
nuclear@33 22 /* command bits */
nuclear@33 23 #define CMD_CHAN0 0
nuclear@33 24 #define CMD_CHAN1 (1 << 6)
nuclear@33 25 #define CMD_CHAN2 (2 << 6)
nuclear@33 26 #define CMD_RDBACK (3 << 6)
nuclear@33 27
nuclear@33 28 #define CMD_LATCH 0
nuclear@33 29 #define CMD_ACCESS_LOW (1 << 4)
nuclear@33 30 #define CMD_ACCESS_HIGH (2 << 4)
nuclear@33 31 #define CMD_ACCESS_BOTH (3 << 4)
nuclear@33 32
nuclear@33 33 #define CMD_OP_INT_TERM 0
nuclear@33 34 #define CMD_OP_ONESHOT (1 << 1)
nuclear@33 35 #define CMD_OP_RATE (2 << 1)
nuclear@33 36 #define CMD_OP_SQWAVE (3 << 1)
nuclear@33 37 #define CMD_OP_SOFT_STROBE (4 << 1)
nuclear@33 38 #define CMD_OP_HW_STROBE (5 << 1)
nuclear@33 39
nuclear@33 40 #define CMD_MODE_BIN 0
nuclear@33 41 #define CMD_MODE_BCD 1
nuclear@33 42
nuclear@33 43
nuclear@51 44 #define MSEC_TO_TICKS(ms) ((ms) * TICK_FREQ_HZ / 1000)
nuclear@51 45
nuclear@51 46 struct timer_event {
nuclear@51 47 int dt; /* remaining ticks delta from the previous event */
nuclear@51 48 struct timer_event *next;
nuclear@51 49 };
nuclear@51 50
nuclear@51 51
nuclear@33 52 static void intr_handler();
nuclear@33 53
nuclear@33 54
nuclear@51 55 static struct timer_event *evlist;
nuclear@51 56
nuclear@51 57
nuclear@33 58 void init_timer(void)
nuclear@33 59 {
nuclear@34 60 /* calculate the reload count: round(osc / freq) */
nuclear@34 61 int reload_count = DIV_ROUND(OSC_FREQ_HZ, TICK_FREQ_HZ);
nuclear@33 62
nuclear@33 63 /* set the mode to square wave for channel 0, both low
nuclear@34 64 * and high reload count bytes will follow...
nuclear@33 65 */
nuclear@33 66 outb(CMD_CHAN0 | CMD_ACCESS_BOTH | CMD_OP_SQWAVE, PORT_CMD);
nuclear@33 67
nuclear@34 68 /* write the low and high bytes of the reload count to the
nuclear@33 69 * port for channel 0
nuclear@33 70 */
nuclear@34 71 outb(reload_count & 0xff, PORT_DATA0);
nuclear@34 72 outb((reload_count >> 8) & 0xff, PORT_DATA0);
nuclear@33 73
nuclear@33 74 /* set the timer interrupt handler */
nuclear@35 75 interrupt(IRQ_TO_INTR(0), intr_handler);
nuclear@33 76 }
nuclear@33 77
nuclear@55 78 void sleep(unsigned long msec)
nuclear@51 79 {
nuclear@51 80 int ticks, tsum, istate;
nuclear@51 81 struct timer_event *ev, *node;
nuclear@51 82
nuclear@55 83 printf("sleep(%lu)\n", msec);
nuclear@51 84
nuclear@51 85 if((ticks = MSEC_TO_TICKS(msec)) <= 0) {
nuclear@55 86 return;
nuclear@51 87 }
nuclear@51 88
nuclear@51 89 if(!(ev = malloc(sizeof *ev))) {
nuclear@55 90 printf("sleep: failed to allocate timer_event structure\n");
nuclear@55 91 return;
nuclear@51 92 }
nuclear@51 93
nuclear@51 94 istate = get_intr_state();
nuclear@51 95 disable_intr();
nuclear@51 96
nuclear@51 97 /* insert at the beginning */
nuclear@51 98 if(!evlist || ticks <= evlist->dt) {
nuclear@51 99 ev->next = evlist;
nuclear@51 100 evlist = ev;
nuclear@51 101
nuclear@51 102 ev->dt = ticks;
nuclear@51 103 if(ev->next) {
nuclear@51 104 ev->next->dt -= ticks;
nuclear@51 105 }
nuclear@55 106 } else {
nuclear@51 107
nuclear@55 108 tsum = evlist->dt;
nuclear@55 109 node = evlist;
nuclear@51 110
nuclear@55 111 while(node->next && ticks > tsum + node->next->dt) {
nuclear@55 112 tsum += node->next->dt;
nuclear@55 113 node = node->next;
nuclear@55 114 }
nuclear@51 115
nuclear@55 116 ev->next = node->next;
nuclear@55 117 node->next = ev;
nuclear@51 118
nuclear@55 119 /* fix the relative times */
nuclear@55 120 ev->dt = ticks - tsum;
nuclear@55 121 if(ev->next) {
nuclear@55 122 ev->next->dt -= ev->dt;
nuclear@55 123 }
nuclear@51 124 }
nuclear@51 125
nuclear@51 126 set_intr_state(istate);
nuclear@55 127
nuclear@55 128 /* wait on the address of this timer event */
nuclear@55 129 wait(ev);
nuclear@51 130 }
nuclear@51 131
nuclear@33 132 /* This will be called by the interrupt dispatcher approximately
nuclear@33 133 * every 1/250th of a second, so it must be extremely fast.
nuclear@33 134 * For now, just increasing a tick counter will suffice.
nuclear@33 135 */
nuclear@51 136 static void intr_handler(int inum)
nuclear@33 137 {
nuclear@51 138 int istate;
nuclear@51 139 struct process *cur_proc;
nuclear@51 140
nuclear@33 141 nticks++;
nuclear@51 142
nuclear@51 143 printf("TICKS: %d\n", nticks);
nuclear@51 144
nuclear@51 145 istate = get_intr_state();
nuclear@51 146 disable_intr();
nuclear@51 147
nuclear@51 148 /* find out if there are any timers that have to go off */
nuclear@51 149 if(evlist) {
nuclear@51 150 evlist->dt--;
nuclear@51 151
nuclear@51 152 while(evlist->dt <= 0) {
nuclear@51 153 struct timer_event *ev = evlist;
nuclear@51 154 evlist = evlist->next;
nuclear@51 155
nuclear@51 156 printf("timer going off!!!\n");
nuclear@55 157 /* wake up all processes waiting on this address */
nuclear@55 158 wakeup(ev);
nuclear@51 159 free(ev);
nuclear@51 160 }
nuclear@51 161 }
nuclear@51 162
nuclear@51 163 if((cur_proc = get_current_proc())) {
nuclear@55 164 /* if the timeslice of this process has expire, call the scheduler */
nuclear@51 165 if(--cur_proc->ticks_left <= 0) {
nuclear@51 166 schedule();
nuclear@51 167 }
nuclear@51 168 }
nuclear@51 169
nuclear@51 170 set_intr_state(istate);
nuclear@33 171 }