aboutsummaryrefslogtreecommitdiff
path: root/hw/timer/hpet.c
blob: 2792f89c66256129ad27901087d21f97f7be92d5 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
/*
 *  High Precisition Event Timer emulation
 *
 *  Copyright (c) 2007 Alexander Graf
 *  Copyright (c) 2008 IBM Corporation
 *
 *  Authors: Beth Kon <bkon@us.ibm.com>
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2 of the License, or (at your option) any later version.
 *
 * This library 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
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, see <http://www.gnu.org/licenses/>.
 *
 * *****************************************************************
 *
 * This driver attempts to emulate an HPET device in software.
 */

#include "hw/hw.h"
#include "hw/i386/pc.h"
#include "ui/console.h"
#include "qemu/timer.h"
#include "hw/timer/hpet.h"
#include "hw/sysbus.h"
#include "hw/timer/mc146818rtc.h"
#include "hw/timer/i8254.h"

//#define HPET_DEBUG
#ifdef HPET_DEBUG
#define DPRINTF printf
#else
#define DPRINTF(...)
#endif

#define HPET_MSI_SUPPORT        0

#define HPET(obj) OBJECT_CHECK(HPETState, (obj), TYPE_HPET)

struct HPETState;
typedef struct HPETTimer {  /* timers */
    uint8_t tn;             /*timer number*/
    QEMUTimer *qemu_timer;
    struct HPETState *state;
    /* Memory-mapped, software visible timer registers */
    uint64_t config;        /* configuration/cap */
    uint64_t cmp;           /* comparator */
    uint64_t fsb;           /* FSB route */
    /* Hidden register state */
    uint64_t period;        /* Last value written to comparator */
    uint8_t wrap_flag;      /* timer pop will indicate wrap for one-shot 32-bit
                             * mode. Next pop will be actual timer expiration.
                             */
} HPETTimer;

typedef struct HPETState {
    /*< private >*/
    SysBusDevice parent_obj;
    /*< public >*/

    MemoryRegion iomem;
    uint64_t hpet_offset;
    qemu_irq irqs[HPET_NUM_IRQ_ROUTES];
    uint32_t flags;
    uint8_t rtc_irq_level;
    qemu_irq pit_enabled;
    uint8_t num_timers;
    uint32_t intcap;
    HPETTimer timer[HPET_MAX_TIMERS];

    /* Memory-mapped, software visible registers */
    uint64_t capability;        /* capabilities */
    uint64_t config;            /* configuration */
    uint64_t isr;               /* interrupt status reg */
    uint64_t hpet_counter;      /* main counter */
    uint8_t  hpet_id;           /* instance id */
} HPETState;

static uint32_t hpet_in_legacy_mode(HPETState *s)
{
    return s->config & HPET_CFG_LEGACY;
}

static uint32_t timer_int_route(struct HPETTimer *timer)
{
    return (timer->config & HPET_TN_INT_ROUTE_MASK) >> HPET_TN_INT_ROUTE_SHIFT;
}

static uint32_t timer_fsb_route(HPETTimer *t)
{
    return t->config & HPET_TN_FSB_ENABLE;
}

static uint32_t hpet_enabled(HPETState *s)
{
    return s->config & HPET_CFG_ENABLE;
}

static uint32_t timer_is_periodic(HPETTimer *t)
{
    return t->config & HPET_TN_PERIODIC;
}

static uint32_t timer_enabled(HPETTimer *t)
{
    return t->config & HPET_TN_ENABLE;
}

static uint32_t hpet_time_after(uint64_t a, uint64_t b)
{
    return ((int32_t)(b) - (int32_t)(a) < 0);
}

static uint32_t hpet_time_after64(uint64_t a, uint64_t b)
{
    return ((int64_t)(b) - (int64_t)(a) < 0);
}

static uint64_t ticks_to_ns(uint64_t value)
{
    return (muldiv64(value, HPET_CLK_PERIOD, FS_PER_NS));
}

static uint64_t ns_to_ticks(uint64_t value)
{
    return (muldiv64(value, FS_PER_NS, HPET_CLK_PERIOD));
}

static uint64_t hpet_fixup_reg(uint64_t new, uint64_t old, uint64_t mask)
{
    new &= mask;
    new |= old & ~mask;
    return new;
}

static int activating_bit(uint64_t old, uint64_t new, uint64_t mask)
{
    return (!(old & mask) && (new & mask));
}

static int deactivating_bit(uint64_t old, uint64_t new, uint64_t mask)
{
    return ((old & mask) && !(new & mask));
}

static uint64_t hpet_get_ticks(HPETState *s)
{
    return ns_to_ticks(qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL) + s->hpet_offset);
}

/*
 * calculate diff between comparator value and current ticks
 */
static inline uint64_t hpet_calculate_diff(HPETTimer *t, uint64_t current)
{

    if (t->config & HPET_TN_32BIT) {
        uint32_t diff, cmp;

        cmp = (uint32_t)t->cmp;
        diff = cmp - (uint32_t)current;
        diff = (int32_t)diff > 0 ? diff : (uint32_t)1;
        return (uint64_t)diff;
    } else {
        uint64_t diff, cmp;

        cmp = t->cmp;
        diff = cmp - current;
        diff = (int64_t)diff > 0 ? diff : (uint64_t)1;
        return diff;
    }
}

static void update_irq(struct HPETTimer *timer, int set)
{
    uint64_t mask;
    HPETState *s;
    int route;

    if (timer->tn <= 1 && hpet_in_legacy_mode(timer->state)) {
        /* if LegacyReplacementRoute bit is set, HPET specification requires
         * timer0 be routed to IRQ0 in NON-APIC or IRQ2 in the I/O APIC,
         * timer1 be routed to IRQ8 in NON-APIC or IRQ8 in the I/O APIC.
         */
        route = (timer->tn == 0) ? 0 : RTC_ISA_IRQ;
    } else {
        route = timer_int_route(timer);
    }
    s = timer->state;
    mask = 1 << timer->tn;
    if (!set || !timer_enabled(timer) || !hpet_enabled(timer->state)) {
        s->isr &= ~mask;
        if (!timer_fsb_route(timer)) {
            /* fold the ICH PIRQ# pin's internal inversion logic into hpet */
            if (route >= ISA_NUM_IRQS) {
                qemu_irq_raise(s->irqs[route]);
            } else {
                qemu_irq_lower(s->irqs[route]);
            }
        }
    } else if (timer_fsb_route(timer)) {
        stl_le_phys(&address_space_memory,
                    timer->fsb >> 32, timer->fsb & 0xffffffff);
    } else if (timer->config & HPET_TN_TYPE_LEVEL) {
        s->isr |= mask;
        /* fold the ICH PIRQ# pin's internal inversion logic into hpet */
        if (route >= ISA_NUM_IRQS) {
            qemu_irq_lower(s->irqs[route]);
        } else {
            qemu_irq_raise(s->irqs[route]);
        }
    } else {
        s->isr &= ~mask;
        qemu_irq_pulse(s->irqs[route]);
    }
}

static void hpet_pre_save(void *opaque)
{
    HPETState *s = opaque;

    /* save current counter value */
    s->hpet_counter = hpet_get_ticks(s);
}

static int hpet_pre_load(void *opaque)
{
    HPETState *s = opaque;

    /* version 1 only supports 3, later versions will load the actual value */
    s->num_timers = HPET_MIN_TIMERS;
    return 0;
}

static bool hpet_validate_num_timers(void *opaque, int version_id)
{
    HPETState *s = opaque;

    if (s->num_timers < HPET_MIN_TIMERS) {
        return false;
    } else if (s->num_timers > HPET_MAX_TIMERS) {
        return false;
    }
    return true;
}

static int hpet_post_load(void *opaque, int version_id)
{
    HPETState *s = opaque;

    /* Recalculate the offset between the main counter and guest time */
    s->hpet_offset = ticks_to_ns(s->hpet_counter) - qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL);

    /* Push number of timers into capability returned via HPET_ID */
    s->capability &= ~HPET_ID_NUM_TIM_MASK;
    s->capability |= (s->num_timers - 1) << HPET_ID_NUM_TIM_SHIFT;
    hpet_cfg.hpet[s->hpet_id].event_timer_block_id = (uint32_t)s->capability;

    /* Derive HPET_MSI_SUPPORT from the capability of the first timer. */
    s->flags &= ~(1 << HPET_MSI_SUPPORT);
    if (s->timer[0].config & HPET_TN_FSB_CAP) {
        s->flags |= 1 << HPET_MSI_SUPPORT;
    }
    return 0;
}

static bool hpet_rtc_irq_level_needed(void *opaque)
{
    HPETState *s = opaque;

    return s->rtc_irq_level != 0;
}

static const VMStateDescription vmstate_hpet_rtc_irq_level = {
    .name = "hpet/rtc_irq_level",
    .version_id = 1,
    .minimum_version_id = 1,
    .minimum_version_id_old = 1,
    .fields      = (VMStateField[]) {
        VMSTATE_UINT8(rtc_irq_level, HPETState),
        VMSTATE_END_OF_LIST()
    }
};

static const VMStateDescription vmstate_hpet_timer = {
    .name = "hpet_timer",
    .version_id = 1,
    .minimum_version_id = 1,
    .minimum_version_id_old = 1,
    .fields      = (VMStateField []) {
        VMSTATE_UINT8(tn, HPETTimer),
        VMSTATE_UINT64(config, HPETTimer),
        VMSTATE_UINT64(cmp, HPETTimer),
        VMSTATE_UINT64(fsb, HPETTimer),
        VMSTATE_UINT64(period, HPETTimer),
        VMSTATE_UINT8(wrap_flag, HPETTimer),
        VMSTATE_TIMER(qemu_timer, HPETTimer),
        VMSTATE_END_OF_LIST()
    }
};

static const VMStateDescription vmstate_hpet = {
    .name = "hpet",
    .version_id = 2,
    .minimum_version_id = 1,
    .minimum_version_id_old = 1,
    .pre_save = hpet_pre_save,
    .pre_load = hpet_pre_load,
    .post_load = hpet_post_load,
    .fields      = (VMStateField []) {
        VMSTATE_UINT64(config, HPETState),
        VMSTATE_UINT64(isr, HPETState),
        VMSTATE_UINT64(hpet_counter, HPETState),
        VMSTATE_UINT8_V(num_timers, HPETState, 2),
        VMSTATE_VALIDATE("num_timers in range", hpet_validate_num_timers),
        VMSTATE_STRUCT_VARRAY_UINT8(timer, HPETState, num_timers, 0,
                                    vmstate_hpet_timer, HPETTimer),
        VMSTATE_END_OF_LIST()
    },
    .subsections = (VMStateSubsection[]) {
        {
            .vmsd = &vmstate_hpet_rtc_irq_level,
            .needed = hpet_rtc_irq_level_needed,
        }, {
            /* empty */
        }
    }
};

/*
 * timer expiration callback
 */
static void hpet_timer(void *opaque)
{
    HPETTimer *t = opaque;
    uint64_t diff;

    uint64_t period = t->period;
    uint64_t cur_tick = hpet_get_ticks(t->state);

    if (timer_is_periodic(t) && period != 0) {
        if (t->config & HPET_TN_32BIT) {
            while (hpet_time_after(cur_tick, t->cmp)) {
                t->cmp = (uint32_t)(t->cmp + t->period);
            }
        } else {
            while (hpet_time_after64(cur_tick, t->cmp)) {
                t->cmp += period;
            }
        }
        diff = hpet_calculate_diff(t, cur_tick);
        timer_mod(t->qemu_timer,
                       qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL) + (int64_t)ticks_to_ns(diff));
    } else if (t->config & HPET_TN_32BIT && !timer_is_periodic(t)) {
        if (t->wrap_flag) {
            diff = hpet_calculate_diff(t, cur_tick);
            timer_mod(t->qemu_timer, qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL) +
                           (int64_t)ticks_to_ns(diff));
            t->wrap_flag = 0;
        }
    }
    update_irq(t, 1);
}

static void hpet_set_timer(HPETTimer *t)
{
    uint64_t diff;
    uint32_t wrap_diff;  /* how many ticks until we wrap? */
    uint64_t cur_tick = hpet_get_ticks(t->state);

    /* whenever new timer is being set up, make sure wrap_flag is 0 */
    t->wrap_flag = 0;
    diff = hpet_calculate_diff(t, cur_tick);

    /* hpet spec says in one-shot 32-bit mode, generate an interrupt when
     * counter wraps in addition to an interrupt with comparator match.
     */
    if (t->config & HPET_TN_32BIT && !timer_is_periodic(t)) {
        wrap_diff = 0xffffffff - (uint32_t)cur_tick;
        if (wrap_diff < (uint32_t)diff) {
            diff = wrap_diff;
            t->wrap_flag = 1;
        }
    }
    timer_mod(t->qemu_timer,
                   qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL) + (int64_t)ticks_to_ns(diff));
}

static void hpet_del_timer(HPETTimer *t)
{
    timer_del(t->qemu_timer);
    update_irq(t, 0);
}

#ifdef HPET_DEBUG
static uint32_t hpet_ram_readb(void *opaque, hwaddr addr)
{
    printf("qemu: hpet_read b at %" PRIx64 "\n", addr);
    return 0;
}

static uint32_t hpet_ram_readw(void *opaque, hwaddr addr)
{
    printf("qemu: hpet_read w at %" PRIx64 "\n", addr);
    return 0;
}
#endif

static uint64_t hpet_ram_read(void *opaque, hwaddr addr,
                              unsigned size)
{
    HPETState *s = opaque;
    uint64_t cur_tick, index;

    DPRINTF("qemu: Enter hpet_ram_readl at %" PRIx64 "\n", addr);
    index = addr;
    /*address range of all TN regs*/
    if (index >= 0x100 && index <= 0x3ff) {
        uint8_t timer_id = (addr - 0x100) / 0x20;
        HPETTimer *timer = &s->timer[timer_id];

        if (timer_id > s->num_timers) {
            DPRINTF("qemu: timer id out of range\n");
            return 0;
        }

        switch ((addr - 0x100) % 0x20) {
        case HPET_TN_CFG:
            return timer->config;
        case HPET_TN_CFG + 4: // Interrupt capabilities
            return timer->config >> 32;
        case HPET_TN_CMP: // comparator register
            return timer->cmp;
        case HPET_TN_CMP + 4:
            return timer->cmp >> 32;
        case HPET_TN_ROUTE:
            return timer->fsb;
        case HPET_TN_ROUTE + 4:
            return timer->fsb >> 32;
        default:
            DPRINTF("qemu: invalid hpet_ram_readl\n");
            break;
        }
    } else {
        switch (index) {
        case HPET_ID:
            return s->capability;
        case HPET_PERIOD:
            return s->capability >> 32;
        case HPET_CFG:
            return s->config;
        case HPET_CFG + 4:
            DPRINTF("qemu: invalid HPET_CFG + 4 hpet_ram_readl\n");
            return 0;
        case HPET_COUNTER:
            if (hpet_enabled(s)) {
                cur_tick = hpet_get_ticks(s);
            } else {
                cur_tick = s->hpet_counter;
            }
            DPRINTF("qemu: reading counter  = %" PRIx64 "\n", cur_tick);
            return cur_tick;
        case HPET_COUNTER + 4:
            if (hpet_enabled(s)) {
                cur_tick = hpet_get_ticks(s);
            } else {
                cur_tick = s->hpet_counter;
            }
            DPRINTF("qemu: reading counter + 4  = %" PRIx64 "\n", cur_tick);
            return cur_tick >> 32;
        case HPET_STATUS:
            return s->isr;
        default:
            DPRINTF("qemu: invalid hpet_ram_readl\n");
            break;
        }
    }
    return 0;
}

static void hpet_ram_write(void *opaque, hwaddr addr,
                           uint64_t value, unsigned size)
{
    int i;
    HPETState *s = opaque;
    uint64_t old_val, new_val, val, index;

    DPRINTF("qemu: Enter hpet_ram_writel at %" PRIx64 " = %#x\n", addr, value);
    index = addr;
    old_val = hpet_ram_read(opaque, addr, 4);
    new_val = value;

    /*address range of all TN regs*/
    if (index >= 0x100 && index <= 0x3ff) {
        uint8_t timer_id = (addr - 0x100) / 0x20;
        HPETTimer *timer = &s->timer[timer_id];

        DPRINTF("qemu: hpet_ram_writel timer_id = %#x\n", timer_id);
        if (timer_id > s->num_timers) {
            DPRINTF("qemu: timer id out of range\n");
            return;
        }
        switch ((addr - 0x100) % 0x20) {
        case HPET_TN_CFG:
            DPRINTF("qemu: hpet_ram_writel HPET_TN_CFG\n");
            if (activating_bit(old_val, new_val, HPET_TN_FSB_ENABLE)) {
                update_irq(timer, 0);
            }
            val = hpet_fixup_reg(new_val, old_val, HPET_TN_CFG_WRITE_MASK);
            timer->config = (timer->config & 0xffffffff00000000ULL) | val;
            if (new_val & HPET_TN_32BIT) {
                timer->cmp = (uint32_t)timer->cmp;
                timer->period = (uint32_t)timer->period;
            }
            if (activating_bit(old_val, new_val, HPET_TN_ENABLE) &&
                hpet_enabled(s)) {
                hpet_set_timer(timer);
            } else if (deactivating_bit(old_val, new_val, HPET_TN_ENABLE)) {
                hpet_del_timer(timer);
            }
            break;
        case HPET_TN_CFG + 4: // Interrupt capabilities
            DPRINTF("qemu: invalid HPET_TN_CFG+4 write\n");
            break;
        case HPET_TN_CMP: // comparator register
            DPRINTF("qemu: hpet_ram_writel HPET_TN_CMP\n");
            if (timer->config & HPET_TN_32BIT) {
                new_val = (uint32_t)new_val;
            }
            if (!timer_is_periodic(timer)
                || (timer->config & HPET_TN_SETVAL)) {
                timer->cmp = (timer->cmp & 0xffffffff00000000ULL) | new_val;
            }
            if (timer_is_periodic(timer)) {
                /*
                 * FIXME: Clamp period to reasonable min value?
                 * Clamp period to reasonable max value
                 */
                new_val &= (timer->config & HPET_TN_32BIT ? ~0u : ~0ull) >> 1;
                timer->period =
                    (timer->period & 0xffffffff00000000ULL) | new_val;
            }
            timer->config &= ~HPET_TN_SETVAL;
            if (hpet_enabled(s)) {
                hpet_set_timer(timer);
            }
            break;
        case HPET_TN_CMP + 4: // comparator register high order
            DPRINTF("qemu: hpet_ram_writel HPET_TN_CMP + 4\n");
            if (!timer_is_periodic(timer)
                || (timer->config & HPET_TN_SETVAL)) {
                timer->cmp = (timer->cmp & 0xffffffffULL) | new_val << 32;
            } else {
                /*
                 * FIXME: Clamp period to reasonable min value?
                 * Clamp period to reasonable max value
                 */
                new_val &= (timer->config & HPET_TN_32BIT ? ~0u : ~0ull) >> 1;
                timer->period =
                    (timer->period & 0xffffffffULL) | new_val << 32;
                }
                timer->config &= ~HPET_TN_SETVAL;
                if (hpet_enabled(s)) {
                    hpet_set_timer(timer);
                }
                break;
        case HPET_TN_ROUTE:
            timer->fsb = (timer->fsb & 0xffffffff00000000ULL) | new_val;
            break;
        case HPET_TN_ROUTE + 4:
            timer->fsb = (new_val << 32) | (timer->fsb & 0xffffffff);
            break;
        default:
            DPRINTF("qemu: invalid hpet_ram_writel\n");
            break;
        }
        return;
    } else {
        switch (index) {
        case HPET_ID:
            return;
        case HPET_CFG:
            val = hpet_fixup_reg(new_val, old_val, HPET_CFG_WRITE_MASK);
            s->config = (s->config & 0xffffffff00000000ULL) | val;
            if (activating_bit(old_val, new_val, HPET_CFG_ENABLE)) {
                /* Enable main counter and interrupt generation. */
                s->hpet_offset =
                    ticks_to_ns(s->hpet_counter) - qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL);
                for (i = 0; i < s->num_timers; i++) {
                    if ((&s->timer[i])->cmp != ~0ULL) {
                        hpet_set_timer(&s->timer[i]);
                    }
                }
            } else if (deactivating_bit(old_val, new_val, HPET_CFG_ENABLE)) {
                /* Halt main counter and disable interrupt generation. */
                s->hpet_counter = hpet_get_ticks(s);
                for (i = 0; i < s->num_timers; i++) {
                    hpet_del_timer(&s->timer[i]);
                }
            }
            /* i8254 and RTC output pins are disabled
             * when HPET is in legacy mode */
            if (activating_bit(old_val, new_val, HPET_CFG_LEGACY)) {
                qemu_set_irq(s->pit_enabled, 0);
                qemu_irq_lower(s->irqs[0]);
                qemu_irq_lower(s->irqs[RTC_ISA_IRQ]);
            } else if (deactivating_bit(old_val, new_val, HPET_CFG_LEGACY)) {
                qemu_irq_lower(s->irqs[0]);
                qemu_set_irq(s->pit_enabled, 1);
                qemu_set_irq(s->irqs[RTC_ISA_IRQ], s->rtc_irq_level);
            }
            break;
        case HPET_CFG + 4:
            DPRINTF("qemu: invalid HPET_CFG+4 write\n");
            break;
        case HPET_STATUS:
            val = new_val & s->isr;
            for (i = 0; i < s->num_timers; i++) {
                if (val & (1 << i)) {
                    update_irq(&s->timer[i], 0);
                }
            }
            break;
        case HPET_COUNTER:
            if (hpet_enabled(s)) {
                DPRINTF("qemu: Writing counter while HPET enabled!\n");
            }
            s->hpet_counter =
                (s->hpet_counter & 0xffffffff00000000ULL) | value;
            DPRINTF("qemu: HPET counter written. ctr = %#x -> %" PRIx64 "\n",
                    value, s->hpet_counter);
            break;
        case HPET_COUNTER + 4:
            if (hpet_enabled(s)) {
                DPRINTF("qemu: Writing counter while HPET enabled!\n");
            }
            s->hpet_counter =
                (s->hpet_counter & 0xffffffffULL) | (((uint64_t)value) << 32);
            DPRINTF("qemu: HPET counter + 4 written. ctr = %#x -> %" PRIx64 "\n",
                    value, s->hpet_counter);
            break;
        default:
            DPRINTF("qemu: invalid hpet_ram_writel\n");
            break;
        }
    }
}

static const MemoryRegionOps hpet_ram_ops = {
    .read = hpet_ram_read,
    .write = hpet_ram_write,
    .valid = {
        .min_access_size = 4,
        .max_access_size = 4,
    },
    .endianness = DEVICE_NATIVE_ENDIAN,
};

static void hpet_reset(DeviceState *d)
{
    HPETState *s = HPET(d);
    SysBusDevice *sbd = SYS_BUS_DEVICE(d);
    int i;

    for (i = 0; i < s->num_timers; i++) {
        HPETTimer *timer = &s->timer[i];

        hpet_del_timer(timer);
        timer->cmp = ~0ULL;
        timer->config = HPET_TN_PERIODIC_CAP | HPET_TN_SIZE_CAP;
        if (s->flags & (1 << HPET_MSI_SUPPORT)) {
            timer->config |= HPET_TN_FSB_CAP;
        }
        /* advertise availability of ioapic int */
        timer->config |=  (uint64_t)s->intcap << 32;
        timer->period = 0ULL;
        timer->wrap_flag = 0;
    }

    qemu_set_irq(s->pit_enabled, 1);
    s->hpet_counter = 0ULL;
    s->hpet_offset = 0ULL;
    s->config = 0ULL;
    hpet_cfg.hpet[s->hpet_id].event_timer_block_id = (uint32_t)s->capability;
    hpet_cfg.hpet[s->hpet_id].address = sbd->mmio[0].addr;

    /* to document that the RTC lowers its output on reset as well */
    s->rtc_irq_level = 0;
}

static void hpet_handle_legacy_irq(void *opaque, int n, int level)
{
    HPETState *s = HPET(opaque);

    if (n == HPET_LEGACY_PIT_INT) {
        if (!hpet_in_legacy_mode(s)) {
            qemu_set_irq(s->irqs[0], level);
        }
    } else {
        s->rtc_irq_level = level;
        if (!hpet_in_legacy_mode(s)) {
            qemu_set_irq(s->irqs[RTC_ISA_IRQ], level);
        }
    }
}

static void hpet_init(Object *obj)
{
    SysBusDevice *sbd = SYS_BUS_DEVICE(obj);
    HPETState *s = HPET(obj);

    /* HPET Area */
    memory_region_init_io(&s->iomem, obj, &hpet_ram_ops, s, "hpet", 0x400);
    sysbus_init_mmio(sbd, &s->iomem);
}

static void hpet_realize(DeviceState *dev, Error **errp)
{
    SysBusDevice *sbd = SYS_BUS_DEVICE(dev);
    HPETState *s = HPET(dev);
    int i;
    HPETTimer *timer;

    if (!s->intcap) {
        error_printf("Hpet's intcap not initialized.\n");
    }
    if (hpet_cfg.count == UINT8_MAX) {
        /* first instance */
        hpet_cfg.count = 0;
    }

    if (hpet_cfg.count == 8) {
        error_setg(errp, "Only 8 instances of HPET is allowed");
        return;
    }

    s->hpet_id = hpet_cfg.count++;

    for (i = 0; i < HPET_NUM_IRQ_ROUTES; i++) {
        sysbus_init_irq(sbd, &s->irqs[i]);
    }

    if (s->num_timers < HPET_MIN_TIMERS) {
        s->num_timers = HPET_MIN_TIMERS;
    } else if (s->num_timers > HPET_MAX_TIMERS) {
        s->num_timers = HPET_MAX_TIMERS;
    }
    for (i = 0; i < HPET_MAX_TIMERS; i++) {
        timer = &s->timer[i];
        timer->qemu_timer = timer_new_ns(QEMU_CLOCK_VIRTUAL, hpet_timer, timer);
        timer->tn = i;
        timer->state = s;
    }

    /* 64-bit main counter; LegacyReplacementRoute. */
    s->capability = 0x8086a001ULL;
    s->capability |= (s->num_timers - 1) << HPET_ID_NUM_TIM_SHIFT;
    s->capability |= ((HPET_CLK_PERIOD) << 32);

    qdev_init_gpio_in(dev, hpet_handle_legacy_irq, 2);
    qdev_init_gpio_out(dev, &s->pit_enabled, 1);
}

static Property hpet_device_properties[] = {
    DEFINE_PROP_UINT8("timers", HPETState, num_timers, HPET_MIN_TIMERS),
    DEFINE_PROP_BIT("msi", HPETState, flags, HPET_MSI_SUPPORT, false),
    DEFINE_PROP_UINT32(HPET_INTCAP, HPETState, intcap, 0),
    DEFINE_PROP_END_OF_LIST(),
};

static void hpet_device_class_init(ObjectClass *klass, void *data)
{
    DeviceClass *dc = DEVICE_CLASS(klass);

    dc->realize = hpet_realize;
    dc->reset = hpet_reset;
    dc->vmsd = &vmstate_hpet;
    dc->props = hpet_device_properties;
}

static const TypeInfo hpet_device_info = {
    .name          = TYPE_HPET,
    .parent        = TYPE_SYS_BUS_DEVICE,
    .instance_size = sizeof(HPETState),
    .instance_init = hpet_init,
    .class_init    = hpet_device_class_init,
};

static void hpet_register_types(void)
{
    type_register_static(&hpet_device_info);
}

type_init(hpet_register_types)