cpu/i386/timer.c

   1 /*
   2  * (C) Copyright 2002
   3  * Daniel Engström, Omicron Ceti AB, daniel@omicron.se.
   4  *
   5  * See file CREDITS for list of people who contributed to this
   6  * project.
   7  *
   8  * This program is free software; you can redistribute it and/or
   9  * modify it under the terms of the GNU General Public License as
  10  * published by the Free Software Foundation; either version 2 of
  11  * the License, or (at your option) any later version.
  12  *
  13  * This program is distributed in the hope that it will be useful,
  14  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  15  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  16  * GNU General Public License for more details.
  17  *
  18  * You should have received a copy of the GNU General Public License
  19  * along with this program; if not, write to the Free Software
  20  * Foundation, Inc., 59 Temple Place, Suite 330, Boston,
  21  * MA 02111-1307 USA
  22  */
  23
  24 #include <common.h>
  25 #include <asm/io.h>
  26 #include <asm/i8254.h>
  27 #include <asm/ibmpc.h>
  28
  29
  30 static volatile unsigned long system_ticks;
  31 static int timer_init_done =0;
  32
  33 static void timer_isr(void *unused)
  34 {
  35         system_ticks++;
  36 }
  37
  38 unsigned long get_system_ticks(void)
  39 {
  40         return system_ticks;
  41 }
  42
  43 #define TIMER0_VALUE 0x04aa /* 1kHz 1.9318MHz / 1000 */
  44 #define TIMER2_VALUE 0x0a8e /* 440Hz */
  45
  46 int timer_init(void)
  47 {
  48         system_ticks = 0;
  49
  50         irq_install_handler(0, timer_isr, NULL);
  51
  52         /* initialize timer 0 and 2
  53          *
  54          * Timer 0 is used to increment system_tick 1000 times/sec
  55          * Timer 1 was used for DRAM refresh in early PC's
  56          * Timer 2 is used to drive the speaker
  57          * (to stasrt a beep: write 3 to port 0x61,
  58          * to stop it again: write 0)
  59          */
  60
  61         outb(PIT_CMD_CTR0|PIT_CMD_BOTH|PIT_CMD_MODE2, PIT_BASE + PIT_COMMAND);
  62         outb(TIMER0_VALUE&0xff, PIT_BASE + PIT_T0);
  63         outb(TIMER0_VALUE>>8, PIT_BASE + PIT_T0);
  64
  65         outb(PIT_CMD_CTR2|PIT_CMD_BOTH|PIT_CMD_MODE3, PIT_BASE + PIT_COMMAND);
  66         outb(TIMER2_VALUE&0xff, PIT_BASE + PIT_T2);
  67         outb(TIMER2_VALUE>>8, PIT_BASE + PIT_T2);
  68
  69         timer_init_done = 1;
  70
  71         return 0;
  72 }
  73
  74
  75 #ifdef CFG_TIMER_GENERIC
  76
  77 /* the unit for these is CFG_HZ */
  78
  79 /* FixMe: implement these */
  80 void reset_timer (void)
  81 {
  82         system_ticks = 0;
  83 }
  84
  85 ulong get_timer (ulong base)
  86 {
  87         return (system_ticks - base);
  88 }
  89
  90 void set_timer (ulong t)
  91 {
  92         system_ticks = t;
  93 }
  94
  95 static u16 read_pit(void)
  96 {
  97         u8 low;
  98         outb(PIT_CMD_LATCH, PIT_BASE + PIT_COMMAND);
  99         low = inb(PIT_BASE + PIT_T0);
 100         return ((inb(PIT_BASE + PIT_T0) << 8) | low);
 101 }
 102
 103 /* this is not very exact */
 104 void udelay (unsigned long usec)
 105 {
 106         int counter;
 107         int wraps;
 108
 109         if (!timer_init_done) {
 110                 return;
 111         }
 112         counter = read_pit();
 113         wraps = usec/1000;
 114         usec = usec%1000;
 115
 116         usec*=1194;
 117         usec/=1000;
 118         usec+=counter;
 119         if (usec > 1194) {
 120                 usec-=1194;
 121                 wraps++;
 122         }
 123
 124         while (1) {
 125                 int new_count = read_pit();
 126
 127                 if (((new_count < usec) && !wraps) || wraps < 0) {
 128                         break;
 129                 }
 130
 131                 if (new_count > counter) {
 132                         wraps--;
 133                 }
 134                 counter = new_count;
 135         }
 136
 137 }
 138
 139 #if 0
 140 /* this is a version with debug output */
 141 void _udelay (unsigned long usec)
 142 {
 143         int counter;
 144         int wraps;
 145
 146         int usec1, usec2, usec3;
 147         int wraps1, wraps2, wraps3, wraps4;
 148         int ctr1, ctr2, ctr3, nct1, nct2;
 149         int i;
 150         usec1=usec;
 151         if (!timer_init_done) {
 152                 return;
 153         }
 154         counter = read_pit();
 155         ctr1 = counter;
 156         wraps = usec/1000;
 157         usec = usec%1000;
 158
 159         usec2 = usec;
 160         wraps1 = wraps;
 161
 162         usec*=1194;
 163         usec/=1000;
 164         usec+=counter;
 165         if (usec > 1194) {
 166                 usec-=1194;
 167                 wraps++;
 168         }
 169
 170         usec3 = usec;
 171         wraps2 = wraps;
 172
 173         ctr2 = wraps3 = nct1 = 4711;
 174         ctr3 = wraps4 = nct2 = 4711;
 175         i=0;
 176         while (1) {
 177                 int new_count = read_pit();
 178                 i++;
 179                 if ((new_count < usec && !wraps) || wraps < 0) {
 180                         break;
 181                 }
 182
 183                 if (new_count > counter) {
 184                         wraps--;
 185                 }
 186                 if (ctr2==4711) {
 187                         ctr2 = counter;
 188                         wraps3 = wraps;
 189                         nct1 = new_count;
 190                 } else {
 191                         ctr3 = counter;
 192                         wraps4 = wraps;
 193                         nct2 = new_count;
 194                 }
 195
 196                 counter = new_count;
 197         }
 198
 199         printf("udelay(%d)\n", usec1);
 200         printf("counter %d\n", ctr1);
 201         printf("1: wraps %d, usec %d\n", wraps1, usec2);
 202         printf("2: wraps %d, usec %d\n", wraps2, usec3);
 203         printf("new_count[0] %d counter %d wraps %d\n", nct1, ctr2, wraps3);
 204         printf("new_count[%d] %d counter %d wraps %d\n", i, nct2, ctr3, wraps4);
 205
 206         printf("%d %d %d %d %d\n",
 207                read_pit(), read_pit(), read_pit(),
 208                read_pit(), read_pit());
 209 }
 210 #endif
 211 #endif