hw/i8254.c

   1 /*
   2  * QEMU 8253/8254 interval timer emulation
   3  *
   4  * Copyright (c) 2003-2004 Fabrice Bellard
   5  *
   6  * Permission is hereby granted, free of charge, to any person obtaining a copy
   7  * of this software and associated documentation files (the "Software"), to deal
   8  * in the Software without restriction, including without limitation the rights
   9  * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
  10  * copies of the Software, and to permit persons to whom the Software is
  11  * furnished to do so, subject to the following conditions:
  12  *
  13  * The above copyright notice and this permission notice shall be included in
  14  * all copies or substantial portions of the Software.
  15  *
  16  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  17  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  18  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
  19  * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  20  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  21  * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
  22  * THE SOFTWARE.
  23  */
  24 #include "hw.h"
  25 #include "pc.h"
  26 #include "isa.h"
  27 #include "qemu-timer.h"
  28
  29 //#define DEBUG_PIT
  30
  31 #define RW_STATE_LSB 1
  32 #define RW_STATE_MSB 2
  33 #define RW_STATE_WORD0 3
  34 #define RW_STATE_WORD1 4
  35
  36 typedef struct PITChannelState {
  37     int count; /* can be 65536 */
  38     uint16_t latched_count;
  39     uint8_t count_latched;
  40     uint8_t status_latched;
  41     uint8_t status;
  42     uint8_t read_state;
  43     uint8_t write_state;
  44     uint8_t write_latch;
  45     uint8_t rw_mode;
  46     uint8_t mode;
  47     uint8_t bcd; /* not supported */
  48     uint8_t gate; /* timer start */
  49     int64_t count_load_time;
  50     /* irq handling */
  51     int64_t next_transition_time;
  52     QEMUTimer *irq_timer;
  53     qemu_irq irq;
  54 } PITChannelState;
  55
  56 struct PITState {
  57     PITChannelState channels[3];
  58 };
  59
  60 static PITState pit_state;
  61
  62 static void pit_irq_timer_update(PITChannelState *s, int64_t current_time);
  63
  64 static int pit_get_count(PITChannelState *s)
  65 {
  66     uint64_t d;
  67     int counter;
  68
  69     d = muldiv64(qemu_get_clock(vm_clock) - s->count_load_time, PIT_FREQ, ticks_per_sec);
  70     switch(s->mode) {
  71     case 0:
  72     case 1:
  73     case 4:
  74     case 5:
  75         counter = (s->count - d) & 0xffff;
  76         break;
  77     case 3:
  78         /* XXX: may be incorrect for odd counts */
  79         counter = s->count - ((2 * d) % s->count);
  80         break;
  81     default:
  82         counter = s->count - (d % s->count);
  83         break;
  84     }
  85     return counter;
  86 }
  87
  88 /* get pit output bit */
  89 static int pit_get_out1(PITChannelState *s, int64_t current_time)
  90 {
  91     uint64_t d;
  92     int out;
  93
  94     d = muldiv64(current_time - s->count_load_time, PIT_FREQ, ticks_per_sec);
  95     switch(s->mode) {
  96     default:
  97     case 0:
  98         out = (d >= s->count);
  99         break;
 100     case 1:
 101         out = (d < s->count);
 102         break;
 103     case 2:
 104         if ((d % s->count) == 0 && d != 0)
 105             out = 1;
 106         else
 107             out = 0;
 108         break;
 109     case 3:
 110         out = (d % s->count) < ((s->count + 1) >> 1);
 111         break;
 112     case 4:
 113     case 5:
 114         out = (d == s->count);
 115         break;
 116     }
 117     return out;
 118 }
 119
 120 int pit_get_out(PITState *pit, int channel, int64_t current_time)
 121 {
 122     PITChannelState *s = &pit->channels[channel];
 123     return pit_get_out1(s, current_time);
 124 }
 125
 126 /* return -1 if no transition will occur.  */
 127 static int64_t pit_get_next_transition_time(PITChannelState *s,
 128                                             int64_t current_time)
 129 {
 130     uint64_t d, next_time, base;
 131     int period2;
 132
 133     d = muldiv64(current_time - s->count_load_time, PIT_FREQ, ticks_per_sec);
 134     switch(s->mode) {
 135     default:
 136     case 0:
 137     case 1:
 138         if (d < s->count)
 139             next_time = s->count;
 140         else
 141             return -1;
 142         break;
 143     case 2:
 144         base = (d / s->count) * s->count;
 145         if ((d - base) == 0 && d != 0)
 146             next_time = base + s->count;
 147         else
 148             next_time = base + s->count + 1;
 149         break;
 150     case 3:
 151         base = (d / s->count) * s->count;
 152         period2 = ((s->count + 1) >> 1);
 153         if ((d - base) < period2)
 154             next_time = base + period2;
 155         else
 156             next_time = base + s->count;
 157         break;
 158     case 4:
 159     case 5:
 160         if (d < s->count)
 161             next_time = s->count;
 162         else if (d == s->count)
 163             next_time = s->count + 1;
 164         else
 165             return -1;
 166         break;
 167     }
 168     /* convert to timer units */
 169     next_time = s->count_load_time + muldiv64(next_time, ticks_per_sec, PIT_FREQ);
 170     /* fix potential rounding problems */
 171     /* XXX: better solution: use a clock at PIT_FREQ Hz */
 172     if (next_time <= current_time)
 173         next_time = current_time + 1;
 174     return next_time;
 175 }
 176
 177 /* val must be 0 or 1 */
 178 void pit_set_gate(PITState *pit, int channel, int val)
 179 {
 180     PITChannelState *s = &pit->channels[channel];
 181
 182     switch(s->mode) {
 183     default:
 184     case 0:
 185     case 4:
 186         /* XXX: just disable/enable counting */
 187         break;
 188     case 1:
 189     case 5:
 190         if (s->gate < val) {
 191             /* restart counting on rising edge */
 192             s->count_load_time = qemu_get_clock(vm_clock);
 193             pit_irq_timer_update(s, s->count_load_time);
 194         }
 195         break;
 196     case 2:
 197     case 3:
 198         if (s->gate < val) {
 199             /* restart counting on rising edge */
 200             s->count_load_time = qemu_get_clock(vm_clock);
 201             pit_irq_timer_update(s, s->count_load_time);
 202         }
 203         /* XXX: disable/enable counting */
 204         break;
 205     }
 206     s->gate = val;
 207 }
 208
 209 int pit_get_gate(PITState *pit, int channel)
 210 {
 211     PITChannelState *s = &pit->channels[channel];
 212     return s->gate;
 213 }
 214
 215 int pit_get_initial_count(PITState *pit, int channel)
 216 {
 217     PITChannelState *s = &pit->channels[channel];
 218     return s->count;
 219 }
 220
 221 int pit_get_mode(PITState *pit, int channel)
 222 {
 223     PITChannelState *s = &pit->channels[channel];
 224     return s->mode;
 225 }
 226
 227 static inline void pit_load_count(PITChannelState *s, int val)
 228 {
 229     if (val == 0)
 230         val = 0x10000;
 231     s->count_load_time = qemu_get_clock(vm_clock);
 232     s->count = val;
 233     pit_irq_timer_update(s, s->count_load_time);
 234 }
 235
 236 /* if already latched, do not latch again */
 237 static void pit_latch_count(PITChannelState *s)
 238 {
 239     if (!s->count_latched) {
 240         s->latched_count = pit_get_count(s);
 241         s->count_latched = s->rw_mode;
 242     }
 243 }
 244
 245 static void pit_ioport_write(void *opaque, uint32_t addr, uint32_t val)
 246 {
 247     PITState *pit = opaque;
 248     int channel, access;
 249     PITChannelState *s;
 250
 251     addr &= 3;
 252     if (addr == 3) {
 253         channel = val >> 6;
 254         if (channel == 3) {
 255             /* read back command */
 256             for(channel = 0; channel < 3; channel++) {
 257                 s = &pit->channels[channel];
 258                 if (val & (2 << channel)) {
 259                     if (!(val & 0x20)) {
 260                         pit_latch_count(s);
 261                     }
 262                     if (!(val & 0x10) && !s->status_latched) {
 263                         /* status latch */
 264                         /* XXX: add BCD and null count */
 265                         s->status =  (pit_get_out1(s, qemu_get_clock(vm_clock)) << 7) |
 266                             (s->rw_mode << 4) |
 267                             (s->mode << 1) |
 268                             s->bcd;
 269                         s->status_latched = 1;
 270                     }
 271                 }
 272             }
 273         } else {
 274             s = &pit->channels[channel];
 275             access = (val >> 4) & 3;
 276             if (access == 0) {
 277                 pit_latch_count(s);
 278             } else {
 279                 s->rw_mode = access;
 280                 s->read_state = access;
 281                 s->write_state = access;
 282
 283                 s->mode = (val >> 1) & 7;
 284                 s->bcd = val & 1;
 285                 /* XXX: update irq timer ? */
 286             }
 287         }
 288     } else {
 289         s = &pit->channels[addr];
 290         switch(s->write_state) {
 291         default:
 292         case RW_STATE_LSB:
 293             pit_load_count(s, val);
 294             break;
 295         case RW_STATE_MSB:
 296             pit_load_count(s, val << 8);
 297             break;
 298         case RW_STATE_WORD0:
 299             s->write_latch = val;
 300             s->write_state = RW_STATE_WORD1;
 301             break;
 302         case RW_STATE_WORD1:
 303             pit_load_count(s, s->write_latch | (val << 8));
 304             s->write_state = RW_STATE_WORD0;
 305             break;
 306         }
 307     }
 308 }
 309
 310 static uint32_t pit_ioport_read(void *opaque, uint32_t addr)
 311 {
 312     PITState *pit = opaque;
 313     int ret, count;
 314     PITChannelState *s;
 315
 316     addr &= 3;
 317     s = &pit->channels[addr];
 318     if (s->status_latched) {
 319         s->status_latched = 0;
 320         ret = s->status;
 321     } else if (s->count_latched) {
 322         switch(s->count_latched) {
 323         default:
 324         case RW_STATE_LSB:
 325             ret = s->latched_count & 0xff;
 326             s->count_latched = 0;
 327             break;
 328         case RW_STATE_MSB:
 329             ret = s->latched_count >> 8;
 330             s->count_latched = 0;
 331             break;
 332         case RW_STATE_WORD0:
 333             ret = s->latched_count & 0xff;
 334             s->count_latched = RW_STATE_MSB;
 335             break;
 336         }
 337     } else {
 338         switch(s->read_state) {
 339         default:
 340         case RW_STATE_LSB:
 341             count = pit_get_count(s);
 342             ret = count & 0xff;
 343             break;
 344         case RW_STATE_MSB:
 345             count = pit_get_count(s);
 346             ret = (count >> 8) & 0xff;
 347             break;
 348         case RW_STATE_WORD0:
 349             count = pit_get_count(s);
 350             ret = count & 0xff;
 351             s->read_state = RW_STATE_WORD1;
 352             break;
 353         case RW_STATE_WORD1:
 354             count = pit_get_count(s);
 355             ret = (count >> 8) & 0xff;
 356             s->read_state = RW_STATE_WORD0;
 357             break;
 358         }
 359     }
 360     return ret;
 361 }
 362
 363 static void pit_irq_timer_update(PITChannelState *s, int64_t current_time)
 364 {
 365     int64_t expire_time;
 366     int irq_level;
 367
 368     if (!s->irq_timer)
 369         return;
 370     expire_time = pit_get_next_transition_time(s, current_time);
 371     irq_level = pit_get_out1(s, current_time);
 372     qemu_set_irq(s->irq, irq_level);
 373 #ifdef DEBUG_PIT
 374     printf("irq_level=%d next_delay=%f\n",
 375            irq_level,
 376            (double)(expire_time - current_time) / ticks_per_sec);
 377 #endif
 378     s->next_transition_time = expire_time;
 379     if (expire_time != -1)
 380         qemu_mod_timer(s->irq_timer, expire_time);
 381     else
 382         qemu_del_timer(s->irq_timer);
 383 }
 384
 385 static void pit_irq_timer(void *opaque)
 386 {
 387     PITChannelState *s = opaque;
 388
 389     pit_irq_timer_update(s, s->next_transition_time);
 390 }
 391
 392 static void pit_save(QEMUFile *f, void *opaque)
 393 {
 394     PITState *pit = opaque;
 395     PITChannelState *s;
 396     int i;
 397
 398     for(i = 0; i < 3; i++) {
 399         s = &pit->channels[i];
 400         qemu_put_be32s(f, &s->count);
 401         qemu_put_be16s(f, &s->latched_count);
 402         qemu_put_8s(f, &s->count_latched);
 403         qemu_put_8s(f, &s->status_latched);
 404         qemu_put_8s(f, &s->status);
 405         qemu_put_8s(f, &s->read_state);
 406         qemu_put_8s(f, &s->write_state);
 407         qemu_put_8s(f, &s->write_latch);
 408         qemu_put_8s(f, &s->rw_mode);
 409         qemu_put_8s(f, &s->mode);
 410         qemu_put_8s(f, &s->bcd);
 411         qemu_put_8s(f, &s->gate);
 412         qemu_put_be64s(f, &s->count_load_time);
 413         if (s->irq_timer) {
 414             qemu_put_be64s(f, &s->next_transition_time);
 415             qemu_put_timer(f, s->irq_timer);
 416         }
 417     }
 418 }
 419
 420 static int pit_load(QEMUFile *f, void *opaque, int version_id)
 421 {
 422     PITState *pit = opaque;
 423     PITChannelState *s;
 424     int i;
 425
 426     if (version_id != 1)
 427         return -EINVAL;
 428
 429     for(i = 0; i < 3; i++) {
 430         s = &pit->channels[i];
 431         qemu_get_be32s(f, &s->count);
 432         qemu_get_be16s(f, &s->latched_count);
 433         qemu_get_8s(f, &s->count_latched);
 434         qemu_get_8s(f, &s->status_latched);
 435         qemu_get_8s(f, &s->status);
 436         qemu_get_8s(f, &s->read_state);
 437         qemu_get_8s(f, &s->write_state);
 438         qemu_get_8s(f, &s->write_latch);
 439         qemu_get_8s(f, &s->rw_mode);
 440         qemu_get_8s(f, &s->mode);
 441         qemu_get_8s(f, &s->bcd);
 442         qemu_get_8s(f, &s->gate);
 443         qemu_get_be64s(f, &s->count_load_time);
 444         if (s->irq_timer) {
 445             qemu_get_be64s(f, &s->next_transition_time);
 446             qemu_get_timer(f, s->irq_timer);
 447         }
 448     }
 449     return 0;
 450 }
 451
 452 static void pit_reset(void *opaque)
 453 {
 454     PITState *pit = opaque;
 455     PITChannelState *s;
 456     int i;
 457
 458     for(i = 0;i < 3; i++) {
 459         s = &pit->channels[i];
 460         s->mode = 3;
 461         s->gate = (i != 2);
 462         pit_load_count(s, 0);
 463     }
 464 }
 465
 466 PITState *pit_init(int base, qemu_irq irq)
 467 {
 468     PITState *pit = &pit_state;
 469     PITChannelState *s;
 470
 471     s = &pit->channels[0];
 472     /* the timer 0 is connected to an IRQ */
 473     s->irq_timer = qemu_new_timer(vm_clock, pit_irq_timer, s);
 474     s->irq = irq;
 475
 476     register_savevm("i8254", base, 1, pit_save, pit_load, pit);
 477
 478     qemu_register_reset(pit_reset, pit);
 479     register_ioport_write(base, 4, 1, pit_ioport_write, pit);
 480     register_ioport_read(base, 3, 1, pit_ioport_read, pit);
 481
 482     pit_reset(pit);
 483
 484     return pit;
 485 }