aboutsummaryrefslogtreecommitdiff
path: root/hw/timer/mc146818rtc.c
blob: b432662bc49119a9d90ba1b280d23d556291eb5b (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
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
/*
 * QEMU MC146818 RTC emulation
 *
 * Copyright (c) 2003-2004 Fabrice Bellard
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 */

#include "qemu/osdep.h"
#include "qemu-common.h"
#include "qemu/cutils.h"
#include "qemu/module.h"
#include "qemu/bcd.h"
#include "hw/hw.h"
#include "hw/irq.h"
#include "qemu/timer.h"
#include "sysemu/sysemu.h"
#include "sysemu/replay.h"
#include "sysemu/reset.h"
#include "hw/timer/mc146818rtc.h"
#include "migration/vmstate.h"
#include "qapi/error.h"
#include "qapi/qapi-commands-misc-target.h"
#include "qapi/qapi-events-misc-target.h"
#include "qapi/visitor.h"
#include "exec/address-spaces.h"

#ifdef TARGET_I386
#include "hw/i386/apic.h"
#endif

//#define DEBUG_CMOS
//#define DEBUG_COALESCED

#ifdef DEBUG_CMOS
# define CMOS_DPRINTF(format, ...)      printf(format, ## __VA_ARGS__)
#else
# define CMOS_DPRINTF(format, ...)      do { } while (0)
#endif

#ifdef DEBUG_COALESCED
# define DPRINTF_C(format, ...)      printf(format, ## __VA_ARGS__)
#else
# define DPRINTF_C(format, ...)      do { } while (0)
#endif

#define SEC_PER_MIN     60
#define MIN_PER_HOUR    60
#define SEC_PER_HOUR    3600
#define HOUR_PER_DAY    24
#define SEC_PER_DAY     86400

#define RTC_REINJECT_ON_ACK_COUNT 20
#define RTC_CLOCK_RATE            32768
#define UIP_HOLD_LENGTH           (8 * NANOSECONDS_PER_SECOND / 32768)

#define MC146818_RTC(obj) OBJECT_CHECK(RTCState, (obj), TYPE_MC146818_RTC)

typedef struct RTCState {
    ISADevice parent_obj;

    MemoryRegion io;
    MemoryRegion coalesced_io;
    uint8_t cmos_data[128];
    uint8_t cmos_index;
    int32_t base_year;
    uint64_t base_rtc;
    uint64_t last_update;
    int64_t offset;
    qemu_irq irq;
    int it_shift;
    /* periodic timer */
    QEMUTimer *periodic_timer;
    int64_t next_periodic_time;
    /* update-ended timer */
    QEMUTimer *update_timer;
    uint64_t next_alarm_time;
    uint16_t irq_reinject_on_ack_count;
    uint32_t irq_coalesced;
    uint32_t period;
    QEMUTimer *coalesced_timer;
    Notifier clock_reset_notifier;
    LostTickPolicy lost_tick_policy;
    Notifier suspend_notifier;
    QLIST_ENTRY(RTCState) link;
} RTCState;

static void rtc_set_time(RTCState *s);
static void rtc_update_time(RTCState *s);
static void rtc_set_cmos(RTCState *s, const struct tm *tm);
static inline int rtc_from_bcd(RTCState *s, int a);
static uint64_t get_next_alarm(RTCState *s);

static inline bool rtc_running(RTCState *s)
{
    return (!(s->cmos_data[RTC_REG_B] & REG_B_SET) &&
            (s->cmos_data[RTC_REG_A] & 0x70) <= 0x20);
}

static uint64_t get_guest_rtc_ns(RTCState *s)
{
    uint64_t guest_clock = qemu_clock_get_ns(rtc_clock);

    return s->base_rtc * NANOSECONDS_PER_SECOND +
        guest_clock - s->last_update + s->offset;
}

static void rtc_coalesced_timer_update(RTCState *s)
{
    if (s->irq_coalesced == 0) {
        timer_del(s->coalesced_timer);
    } else {
        /* divide each RTC interval to 2 - 8 smaller intervals */
        int c = MIN(s->irq_coalesced, 7) + 1;
        int64_t next_clock = qemu_clock_get_ns(rtc_clock) +
            periodic_clock_to_ns(s->period / c);
        timer_mod(s->coalesced_timer, next_clock);
    }
}

static QLIST_HEAD(, RTCState) rtc_devices =
    QLIST_HEAD_INITIALIZER(rtc_devices);

#ifdef TARGET_I386
void qmp_rtc_reset_reinjection(Error **errp)
{
    RTCState *s;

    QLIST_FOREACH(s, &rtc_devices, link) {
        s->irq_coalesced = 0;
    }
}

static bool rtc_policy_slew_deliver_irq(RTCState *s)
{
    apic_reset_irq_delivered();
    qemu_irq_raise(s->irq);
    return apic_get_irq_delivered();
}

static void rtc_coalesced_timer(void *opaque)
{
    RTCState *s = opaque;

    if (s->irq_coalesced != 0) {
        s->cmos_data[RTC_REG_C] |= 0xc0;
        DPRINTF_C("cmos: injecting from timer\n");
        if (rtc_policy_slew_deliver_irq(s)) {
            s->irq_coalesced--;
            DPRINTF_C("cmos: coalesced irqs decreased to %d\n",
                      s->irq_coalesced);
        }
    }

    rtc_coalesced_timer_update(s);
}
#else
static bool rtc_policy_slew_deliver_irq(RTCState *s)
{
    assert(0);
    return false;
}
#endif

static uint32_t rtc_periodic_clock_ticks(RTCState *s)
{
    int period_code;

    if (!(s->cmos_data[RTC_REG_B] & REG_B_PIE)) {
        return 0;
     }

    period_code = s->cmos_data[RTC_REG_A] & 0x0f;

    return periodic_period_to_clock(period_code);
}

/*
 * handle periodic timer. @old_period indicates the periodic timer update
 * is just due to period adjustment.
 */
static void
periodic_timer_update(RTCState *s, int64_t current_time, uint32_t old_period)
{
    uint32_t period;
    int64_t cur_clock, next_irq_clock, lost_clock = 0;

    period = rtc_periodic_clock_ticks(s);

    if (period) {
        /* compute 32 khz clock */
        cur_clock =
            muldiv64(current_time, RTC_CLOCK_RATE, NANOSECONDS_PER_SECOND);

        /*
        * if the periodic timer's update is due to period re-configuration,
        * we should count the clock since last interrupt.
        */
        if (old_period) {
            int64_t last_periodic_clock, next_periodic_clock;

            next_periodic_clock = muldiv64(s->next_periodic_time,
                                    RTC_CLOCK_RATE, NANOSECONDS_PER_SECOND);
            last_periodic_clock = next_periodic_clock - old_period;
            lost_clock = cur_clock - last_periodic_clock;
            assert(lost_clock >= 0);
        }

        /*
         * s->irq_coalesced can change for two reasons:
         *
         * a) if one or more periodic timer interrupts have been lost,
         *    lost_clock will be more that a period.
         *
         * b) when the period may be reconfigured, we expect the OS to
         *    treat delayed tick as the new period.  So, when switching
         *    from a shorter to a longer period, scale down the missing,
         *    because the OS will treat past delayed ticks as longer
         *    (leftovers are put back into lost_clock).  When switching
         *    to a shorter period, scale up the missing ticks since the
         *    OS handler will treat past delayed ticks as shorter.
         */
        if (s->lost_tick_policy == LOST_TICK_POLICY_SLEW) {
            uint32_t old_irq_coalesced = s->irq_coalesced;

            s->period = period;
            lost_clock += old_irq_coalesced * old_period;
            s->irq_coalesced = lost_clock / s->period;
            lost_clock %= s->period;
            if (old_irq_coalesced != s->irq_coalesced ||
                old_period != s->period) {
                DPRINTF_C("cmos: coalesced irqs scaled from %d to %d, "
                          "period scaled from %d to %d\n", old_irq_coalesced,
                          s->irq_coalesced, old_period, s->period);
                rtc_coalesced_timer_update(s);
            }
        } else {
           /*
             * no way to compensate the interrupt if LOST_TICK_POLICY_SLEW
             * is not used, we should make the time progress anyway.
             */
            lost_clock = MIN(lost_clock, period);
        }

        assert(lost_clock >= 0 && lost_clock <= period);

        next_irq_clock = cur_clock + period - lost_clock;
        s->next_periodic_time = periodic_clock_to_ns(next_irq_clock) + 1;
        timer_mod(s->periodic_timer, s->next_periodic_time);
    } else {
        s->irq_coalesced = 0;
        timer_del(s->periodic_timer);
    }
}

static void rtc_periodic_timer(void *opaque)
{
    RTCState *s = opaque;

    periodic_timer_update(s, s->next_periodic_time, 0);
    s->cmos_data[RTC_REG_C] |= REG_C_PF;
    if (s->cmos_data[RTC_REG_B] & REG_B_PIE) {
        s->cmos_data[RTC_REG_C] |= REG_C_IRQF;
        if (s->lost_tick_policy == LOST_TICK_POLICY_SLEW) {
            if (s->irq_reinject_on_ack_count >= RTC_REINJECT_ON_ACK_COUNT)
                s->irq_reinject_on_ack_count = 0;
            if (!rtc_policy_slew_deliver_irq(s)) {
                s->irq_coalesced++;
                rtc_coalesced_timer_update(s);
                DPRINTF_C("cmos: coalesced irqs increased to %d\n",
                          s->irq_coalesced);
            }
        } else
            qemu_irq_raise(s->irq);
    }
}

/* handle update-ended timer */
static void check_update_timer(RTCState *s)
{
    uint64_t next_update_time;
    uint64_t guest_nsec;
    int next_alarm_sec;

    /* From the data sheet: "Holding the dividers in reset prevents
     * interrupts from operating, while setting the SET bit allows"
     * them to occur.
     */
    if ((s->cmos_data[RTC_REG_A] & 0x60) == 0x60) {
        assert((s->cmos_data[RTC_REG_A] & REG_A_UIP) == 0);
        timer_del(s->update_timer);
        return;
    }

    guest_nsec = get_guest_rtc_ns(s) % NANOSECONDS_PER_SECOND;
    next_update_time = qemu_clock_get_ns(rtc_clock)
        + NANOSECONDS_PER_SECOND - guest_nsec;

    /* Compute time of next alarm.  One second is already accounted
     * for in next_update_time.
     */
    next_alarm_sec = get_next_alarm(s);
    s->next_alarm_time = next_update_time +
                         (next_alarm_sec - 1) * NANOSECONDS_PER_SECOND;

    /* If update_in_progress latched the UIP bit, we must keep the timer
     * programmed to the next second, so that UIP is cleared.  Otherwise,
     * if UF is already set, we might be able to optimize.
     */
    if (!(s->cmos_data[RTC_REG_A] & REG_A_UIP) &&
        (s->cmos_data[RTC_REG_C] & REG_C_UF)) {
        /* If AF cannot change (i.e. either it is set already, or
         * SET=1 and then the time is not updated), nothing to do.
         */
        if ((s->cmos_data[RTC_REG_B] & REG_B_SET) ||
            (s->cmos_data[RTC_REG_C] & REG_C_AF)) {
            timer_del(s->update_timer);
            return;
        }

        /* UF is set, but AF is clear.  Program the timer to target
         * the alarm time.  */
        next_update_time = s->next_alarm_time;
    }
    if (next_update_time != timer_expire_time_ns(s->update_timer)) {
        timer_mod(s->update_timer, next_update_time);
    }
}

static inline uint8_t convert_hour(RTCState *s, uint8_t hour)
{
    if (!(s->cmos_data[RTC_REG_B] & REG_B_24H)) {
        hour %= 12;
        if (s->cmos_data[RTC_HOURS] & 0x80) {
            hour += 12;
        }
    }
    return hour;
}

static uint64_t get_next_alarm(RTCState *s)
{
    int32_t alarm_sec, alarm_min, alarm_hour, cur_hour, cur_min, cur_sec;
    int32_t hour, min, sec;

    rtc_update_time(s);

    alarm_sec = rtc_from_bcd(s, s->cmos_data[RTC_SECONDS_ALARM]);
    alarm_min = rtc_from_bcd(s, s->cmos_data[RTC_MINUTES_ALARM]);
    alarm_hour = rtc_from_bcd(s, s->cmos_data[RTC_HOURS_ALARM]);
    alarm_hour = alarm_hour == -1 ? -1 : convert_hour(s, alarm_hour);

    cur_sec = rtc_from_bcd(s, s->cmos_data[RTC_SECONDS]);
    cur_min = rtc_from_bcd(s, s->cmos_data[RTC_MINUTES]);
    cur_hour = rtc_from_bcd(s, s->cmos_data[RTC_HOURS]);
    cur_hour = convert_hour(s, cur_hour);

    if (alarm_hour == -1) {
        alarm_hour = cur_hour;
        if (alarm_min == -1) {
            alarm_min = cur_min;
            if (alarm_sec == -1) {
                alarm_sec = cur_sec + 1;
            } else if (cur_sec > alarm_sec) {
                alarm_min++;
            }
        } else if (cur_min == alarm_min) {
            if (alarm_sec == -1) {
                alarm_sec = cur_sec + 1;
            } else {
                if (cur_sec > alarm_sec) {
                    alarm_hour++;
                }
            }
            if (alarm_sec == SEC_PER_MIN) {
                /* wrap to next hour, minutes is not in don't care mode */
                alarm_sec = 0;
                alarm_hour++;
            }
        } else if (cur_min > alarm_min) {
            alarm_hour++;
        }
    } else if (cur_hour == alarm_hour) {
        if (alarm_min == -1) {
            alarm_min = cur_min;
            if (alarm_sec == -1) {
                alarm_sec = cur_sec + 1;
            } else if (cur_sec > alarm_sec) {
                alarm_min++;
            }

            if (alarm_sec == SEC_PER_MIN) {
                alarm_sec = 0;
                alarm_min++;
            }
            /* wrap to next day, hour is not in don't care mode */
            alarm_min %= MIN_PER_HOUR;
        } else if (cur_min == alarm_min) {
            if (alarm_sec == -1) {
                alarm_sec = cur_sec + 1;
            }
            /* wrap to next day, hours+minutes not in don't care mode */
            alarm_sec %= SEC_PER_MIN;
        }
    }

    /* values that are still don't care fire at the next min/sec */
    if (alarm_min == -1) {
        alarm_min = 0;
    }
    if (alarm_sec == -1) {
        alarm_sec = 0;
    }

    /* keep values in range */
    if (alarm_sec == SEC_PER_MIN) {
        alarm_sec = 0;
        alarm_min++;
    }
    if (alarm_min == MIN_PER_HOUR) {
        alarm_min = 0;
        alarm_hour++;
    }
    alarm_hour %= HOUR_PER_DAY;

    hour = alarm_hour - cur_hour;
    min = hour * MIN_PER_HOUR + alarm_min - cur_min;
    sec = min * SEC_PER_MIN + alarm_sec - cur_sec;
    return sec <= 0 ? sec + SEC_PER_DAY : sec;
}

static void rtc_update_timer(void *opaque)
{
    RTCState *s = opaque;
    int32_t irqs = REG_C_UF;
    int32_t new_irqs;

    assert((s->cmos_data[RTC_REG_A] & 0x60) != 0x60);

    /* UIP might have been latched, update time and clear it.  */
    rtc_update_time(s);
    s->cmos_data[RTC_REG_A] &= ~REG_A_UIP;

    if (qemu_clock_get_ns(rtc_clock) >= s->next_alarm_time) {
        irqs |= REG_C_AF;
        if (s->cmos_data[RTC_REG_B] & REG_B_AIE) {
            qemu_system_wakeup_request(QEMU_WAKEUP_REASON_RTC, NULL);
        }
    }

    new_irqs = irqs & ~s->cmos_data[RTC_REG_C];
    s->cmos_data[RTC_REG_C] |= irqs;
    if ((new_irqs & s->cmos_data[RTC_REG_B]) != 0) {
        s->cmos_data[RTC_REG_C] |= REG_C_IRQF;
        qemu_irq_raise(s->irq);
    }
    check_update_timer(s);
}

static void cmos_ioport_write(void *opaque, hwaddr addr,
                              uint64_t data, unsigned size)
{
    RTCState *s = opaque;
    uint32_t old_period;
    bool update_periodic_timer;

    if ((addr & 1) == 0) {
        s->cmos_index = data & 0x7f;
    } else {
        CMOS_DPRINTF("cmos: write index=0x%02x val=0x%02" PRIx64 "\n",
                     s->cmos_index, data);
        switch(s->cmos_index) {
        case RTC_SECONDS_ALARM:
        case RTC_MINUTES_ALARM:
        case RTC_HOURS_ALARM:
            s->cmos_data[s->cmos_index] = data;
            check_update_timer(s);
            break;
        case RTC_IBM_PS2_CENTURY_BYTE:
            s->cmos_index = RTC_CENTURY;
            /* fall through */
        case RTC_CENTURY:
        case RTC_SECONDS:
        case RTC_MINUTES:
        case RTC_HOURS:
        case RTC_DAY_OF_WEEK:
        case RTC_DAY_OF_MONTH:
        case RTC_MONTH:
        case RTC_YEAR:
            s->cmos_data[s->cmos_index] = data;
            /* if in set mode, do not update the time */
            if (rtc_running(s)) {
                rtc_set_time(s);
                check_update_timer(s);
            }
            break;
        case RTC_REG_A:
            update_periodic_timer = (s->cmos_data[RTC_REG_A] ^ data) & 0x0f;
            old_period = rtc_periodic_clock_ticks(s);

            if ((data & 0x60) == 0x60) {
                if (rtc_running(s)) {
                    rtc_update_time(s);
                }
                /* What happens to UIP when divider reset is enabled is
                 * unclear from the datasheet.  Shouldn't matter much
                 * though.
                 */
                s->cmos_data[RTC_REG_A] &= ~REG_A_UIP;
            } else if (((s->cmos_data[RTC_REG_A] & 0x60) == 0x60) &&
                    (data & 0x70)  <= 0x20) {
                /* when the divider reset is removed, the first update cycle
                 * begins one-half second later*/
                if (!(s->cmos_data[RTC_REG_B] & REG_B_SET)) {
                    s->offset = 500000000;
                    rtc_set_time(s);
                }
                s->cmos_data[RTC_REG_A] &= ~REG_A_UIP;
            }
            /* UIP bit is read only */
            s->cmos_data[RTC_REG_A] = (data & ~REG_A_UIP) |
                (s->cmos_data[RTC_REG_A] & REG_A_UIP);

            if (update_periodic_timer) {
                periodic_timer_update(s, qemu_clock_get_ns(rtc_clock),
                                      old_period);
            }

            check_update_timer(s);
            break;
        case RTC_REG_B:
            update_periodic_timer = (s->cmos_data[RTC_REG_B] ^ data)
                                       & REG_B_PIE;
            old_period = rtc_periodic_clock_ticks(s);

            if (data & REG_B_SET) {
                /* update cmos to when the rtc was stopping */
                if (rtc_running(s)) {
                    rtc_update_time(s);
                }
                /* set mode: reset UIP mode */
                s->cmos_data[RTC_REG_A] &= ~REG_A_UIP;
                data &= ~REG_B_UIE;
            } else {
                /* if disabling set mode, update the time */
                if ((s->cmos_data[RTC_REG_B] & REG_B_SET) &&
                    (s->cmos_data[RTC_REG_A] & 0x70) <= 0x20) {
                    s->offset = get_guest_rtc_ns(s) % NANOSECONDS_PER_SECOND;
                    rtc_set_time(s);
                }
            }
            /* if an interrupt flag is already set when the interrupt
             * becomes enabled, raise an interrupt immediately.  */
            if (data & s->cmos_data[RTC_REG_C] & REG_C_MASK) {
                s->cmos_data[RTC_REG_C] |= REG_C_IRQF;
                qemu_irq_raise(s->irq);
            } else {
                s->cmos_data[RTC_REG_C] &= ~REG_C_IRQF;
                qemu_irq_lower(s->irq);
            }
            s->cmos_data[RTC_REG_B] = data;

            if (update_periodic_timer) {
                periodic_timer_update(s, qemu_clock_get_ns(rtc_clock),
                                      old_period);
            }

            check_update_timer(s);
            break;
        case RTC_REG_C:
        case RTC_REG_D:
            /* cannot write to them */
            break;
        default:
            s->cmos_data[s->cmos_index] = data;
            break;
        }
    }
}

static inline int rtc_to_bcd(RTCState *s, int a)
{
    if (s->cmos_data[RTC_REG_B] & REG_B_DM) {
        return a;
    } else {
        return ((a / 10) << 4) | (a % 10);
    }
}

static inline int rtc_from_bcd(RTCState *s, int a)
{
    if ((a & 0xc0) == 0xc0) {
        return -1;
    }
    if (s->cmos_data[RTC_REG_B] & REG_B_DM) {
        return a;
    } else {
        return ((a >> 4) * 10) + (a & 0x0f);
    }
}

static void rtc_get_time(RTCState *s, struct tm *tm)
{
    tm->tm_sec = rtc_from_bcd(s, s->cmos_data[RTC_SECONDS]);
    tm->tm_min = rtc_from_bcd(s, s->cmos_data[RTC_MINUTES]);
    tm->tm_hour = rtc_from_bcd(s, s->cmos_data[RTC_HOURS] & 0x7f);
    if (!(s->cmos_data[RTC_REG_B] & REG_B_24H)) {
        tm->tm_hour %= 12;
        if (s->cmos_data[RTC_HOURS] & 0x80) {
            tm->tm_hour += 12;
        }
    }
    tm->tm_wday = rtc_from_bcd(s, s->cmos_data[RTC_DAY_OF_WEEK]) - 1;
    tm->tm_mday = rtc_from_bcd(s, s->cmos_data[RTC_DAY_OF_MONTH]);
    tm->tm_mon = rtc_from_bcd(s, s->cmos_data[RTC_MONTH]) - 1;
    tm->tm_year =
        rtc_from_bcd(s, s->cmos_data[RTC_YEAR]) + s->base_year +
        rtc_from_bcd(s, s->cmos_data[RTC_CENTURY]) * 100 - 1900;
}

static void rtc_set_time(RTCState *s)
{
    struct tm tm;

    rtc_get_time(s, &tm);
    s->base_rtc = mktimegm(&tm);
    s->last_update = qemu_clock_get_ns(rtc_clock);

    qapi_event_send_rtc_change(qemu_timedate_diff(&tm));
}

static void rtc_set_cmos(RTCState *s, const struct tm *tm)
{
    int year;

    s->cmos_data[RTC_SECONDS] = rtc_to_bcd(s, tm->tm_sec);
    s->cmos_data[RTC_MINUTES] = rtc_to_bcd(s, tm->tm_min);
    if (s->cmos_data[RTC_REG_B] & REG_B_24H) {
        /* 24 hour format */
        s->cmos_data[RTC_HOURS] = rtc_to_bcd(s, tm->tm_hour);
    } else {
        /* 12 hour format */
        int h = (tm->tm_hour % 12) ? tm->tm_hour % 12 : 12;
        s->cmos_data[RTC_HOURS] = rtc_to_bcd(s, h);
        if (tm->tm_hour >= 12)
            s->cmos_data[RTC_HOURS] |= 0x80;
    }
    s->cmos_data[RTC_DAY_OF_WEEK] = rtc_to_bcd(s, tm->tm_wday + 1);
    s->cmos_data[RTC_DAY_OF_MONTH] = rtc_to_bcd(s, tm->tm_mday);
    s->cmos_data[RTC_MONTH] = rtc_to_bcd(s, tm->tm_mon + 1);
    year = tm->tm_year + 1900 - s->base_year;
    s->cmos_data[RTC_YEAR] = rtc_to_bcd(s, year % 100);
    s->cmos_data[RTC_CENTURY] = rtc_to_bcd(s, year / 100);
}

static void rtc_update_time(RTCState *s)
{
    struct tm ret;
    time_t guest_sec;
    int64_t guest_nsec;

    guest_nsec = get_guest_rtc_ns(s);
    guest_sec = guest_nsec / NANOSECONDS_PER_SECOND;
    gmtime_r(&guest_sec, &ret);

    /* Is SET flag of Register B disabled? */
    if ((s->cmos_data[RTC_REG_B] & REG_B_SET) == 0) {
        rtc_set_cmos(s, &ret);
    }
}

static int update_in_progress(RTCState *s)
{
    int64_t guest_nsec;

    if (!rtc_running(s)) {
        return 0;
    }
    if (timer_pending(s->update_timer)) {
        int64_t next_update_time = timer_expire_time_ns(s->update_timer);
        /* Latch UIP until the timer expires.  */
        if (qemu_clock_get_ns(rtc_clock) >=
            (next_update_time - UIP_HOLD_LENGTH)) {
            s->cmos_data[RTC_REG_A] |= REG_A_UIP;
            return 1;
        }
    }

    guest_nsec = get_guest_rtc_ns(s);
    /* UIP bit will be set at last 244us of every second. */
    if ((guest_nsec % NANOSECONDS_PER_SECOND) >=
        (NANOSECONDS_PER_SECOND - UIP_HOLD_LENGTH)) {
        return 1;
    }
    return 0;
}

static uint64_t cmos_ioport_read(void *opaque, hwaddr addr,
                                 unsigned size)
{
    RTCState *s = opaque;
    int ret;
    if ((addr & 1) == 0) {
        return 0xff;
    } else {
        switch(s->cmos_index) {
        case RTC_IBM_PS2_CENTURY_BYTE:
            s->cmos_index = RTC_CENTURY;
            /* fall through */
        case RTC_CENTURY:
        case RTC_SECONDS:
        case RTC_MINUTES:
        case RTC_HOURS:
        case RTC_DAY_OF_WEEK:
        case RTC_DAY_OF_MONTH:
        case RTC_MONTH:
        case RTC_YEAR:
            /* if not in set mode, calibrate cmos before
             * reading*/
            if (rtc_running(s)) {
                rtc_update_time(s);
            }
            ret = s->cmos_data[s->cmos_index];
            break;
        case RTC_REG_A:
            ret = s->cmos_data[s->cmos_index];
            if (update_in_progress(s)) {
                ret |= REG_A_UIP;
            }
            break;
        case RTC_REG_C:
            ret = s->cmos_data[s->cmos_index];
            qemu_irq_lower(s->irq);
            s->cmos_data[RTC_REG_C] = 0x00;
            if (ret & (REG_C_UF | REG_C_AF)) {
                check_update_timer(s);
            }

            if(s->irq_coalesced &&
                    (s->cmos_data[RTC_REG_B] & REG_B_PIE) &&
                    s->irq_reinject_on_ack_count < RTC_REINJECT_ON_ACK_COUNT) {
                s->irq_reinject_on_ack_count++;
                s->cmos_data[RTC_REG_C] |= REG_C_IRQF | REG_C_PF;
                DPRINTF_C("cmos: injecting on ack\n");
                if (rtc_policy_slew_deliver_irq(s)) {
                    s->irq_coalesced--;
                    DPRINTF_C("cmos: coalesced irqs decreased to %d\n",
                              s->irq_coalesced);
                }
            }
            break;
        default:
            ret = s->cmos_data[s->cmos_index];
            break;
        }
        CMOS_DPRINTF("cmos: read index=0x%02x val=0x%02x\n",
                     s->cmos_index, ret);
        return ret;
    }
}

void rtc_set_memory(ISADevice *dev, int addr, int val)
{
    RTCState *s = MC146818_RTC(dev);
    if (addr >= 0 && addr <= 127)
        s->cmos_data[addr] = val;
}

int rtc_get_memory(ISADevice *dev, int addr)
{
    RTCState *s = MC146818_RTC(dev);
    assert(addr >= 0 && addr <= 127);
    return s->cmos_data[addr];
}

static void rtc_set_date_from_host(ISADevice *dev)
{
    RTCState *s = MC146818_RTC(dev);
    struct tm tm;

    qemu_get_timedate(&tm, 0);

    s->base_rtc = mktimegm(&tm);
    s->last_update = qemu_clock_get_ns(rtc_clock);
    s->offset = 0;

    /* set the CMOS date */
    rtc_set_cmos(s, &tm);
}

static int rtc_pre_save(void *opaque)
{
    RTCState *s = opaque;

    rtc_update_time(s);

    return 0;
}

static int rtc_post_load(void *opaque, int version_id)
{
    RTCState *s = opaque;

    if (version_id <= 2 || rtc_clock == QEMU_CLOCK_REALTIME) {
        rtc_set_time(s);
        s->offset = 0;
        check_update_timer(s);
    }

    /* The periodic timer is deterministic in record/replay mode,
     * so there is no need to update it after loading the vmstate.
     * Reading RTC here would misalign record and replay.
     */
    if (replay_mode == REPLAY_MODE_NONE) {
        uint64_t now = qemu_clock_get_ns(rtc_clock);
        if (now < s->next_periodic_time ||
            now > (s->next_periodic_time + get_max_clock_jump())) {
            periodic_timer_update(s, qemu_clock_get_ns(rtc_clock), 0);
        }
    }

    if (version_id >= 2) {
        if (s->lost_tick_policy == LOST_TICK_POLICY_SLEW) {
            rtc_coalesced_timer_update(s);
        }
    }
    return 0;
}

static bool rtc_irq_reinject_on_ack_count_needed(void *opaque)
{
    RTCState *s = (RTCState *)opaque;
    return s->irq_reinject_on_ack_count != 0;
}

static const VMStateDescription vmstate_rtc_irq_reinject_on_ack_count = {
    .name = "mc146818rtc/irq_reinject_on_ack_count",
    .version_id = 1,
    .minimum_version_id = 1,
    .needed = rtc_irq_reinject_on_ack_count_needed,
    .fields = (VMStateField[]) {
        VMSTATE_UINT16(irq_reinject_on_ack_count, RTCState),
        VMSTATE_END_OF_LIST()
    }
};

static const VMStateDescription vmstate_rtc = {
    .name = "mc146818rtc",
    .version_id = 3,
    .minimum_version_id = 1,
    .pre_save = rtc_pre_save,
    .post_load = rtc_post_load,
    .fields = (VMStateField[]) {
        VMSTATE_BUFFER(cmos_data, RTCState),
        VMSTATE_UINT8(cmos_index, RTCState),
        VMSTATE_UNUSED(7*4),
        VMSTATE_TIMER_PTR(periodic_timer, RTCState),
        VMSTATE_INT64(next_periodic_time, RTCState),
        VMSTATE_UNUSED(3*8),
        VMSTATE_UINT32_V(irq_coalesced, RTCState, 2),
        VMSTATE_UINT32_V(period, RTCState, 2),
        VMSTATE_UINT64_V(base_rtc, RTCState, 3),
        VMSTATE_UINT64_V(last_update, RTCState, 3),
        VMSTATE_INT64_V(offset, RTCState, 3),
        VMSTATE_TIMER_PTR_V(update_timer, RTCState, 3),
        VMSTATE_UINT64_V(next_alarm_time, RTCState, 3),
        VMSTATE_END_OF_LIST()
    },
    .subsections = (const VMStateDescription*[]) {
        &vmstate_rtc_irq_reinject_on_ack_count,
        NULL
    }
};

static void rtc_notify_clock_reset(Notifier *notifier, void *data)
{
    RTCState *s = container_of(notifier, RTCState, clock_reset_notifier);
    int64_t now = *(int64_t *)data;

    rtc_set_date_from_host(ISA_DEVICE(s));
    periodic_timer_update(s, now, 0);
    check_update_timer(s);

    if (s->lost_tick_policy == LOST_TICK_POLICY_SLEW) {
        rtc_coalesced_timer_update(s);
    }
}

/* set CMOS shutdown status register (index 0xF) as S3_resume(0xFE)
   BIOS will read it and start S3 resume at POST Entry */
static void rtc_notify_suspend(Notifier *notifier, void *data)
{
    RTCState *s = container_of(notifier, RTCState, suspend_notifier);
    rtc_set_memory(ISA_DEVICE(s), 0xF, 0xFE);
}

static void rtc_reset(void *opaque)
{
    RTCState *s = opaque;

    s->cmos_data[RTC_REG_B] &= ~(REG_B_PIE | REG_B_AIE | REG_B_SQWE);
    s->cmos_data[RTC_REG_C] &= ~(REG_C_UF | REG_C_IRQF | REG_C_PF | REG_C_AF);
    check_update_timer(s);

    qemu_irq_lower(s->irq);

    if (s->lost_tick_policy == LOST_TICK_POLICY_SLEW) {
        s->irq_coalesced = 0;
        s->irq_reinject_on_ack_count = 0;
    }
}

static const MemoryRegionOps cmos_ops = {
    .read = cmos_ioport_read,
    .write = cmos_ioport_write,
    .impl = {
        .min_access_size = 1,
        .max_access_size = 1,
    },
    .endianness = DEVICE_LITTLE_ENDIAN,
};

static void rtc_get_date(Object *obj, struct tm *current_tm, Error **errp)
{
    RTCState *s = MC146818_RTC(obj);

    rtc_update_time(s);
    rtc_get_time(s, current_tm);
}

static void rtc_realizefn(DeviceState *dev, Error **errp)
{
    ISADevice *isadev = ISA_DEVICE(dev);
    RTCState *s = MC146818_RTC(dev);
    int base = 0x70;

    s->cmos_data[RTC_REG_A] = 0x26;
    s->cmos_data[RTC_REG_B] = 0x02;
    s->cmos_data[RTC_REG_C] = 0x00;
    s->cmos_data[RTC_REG_D] = 0x80;

    /* This is for historical reasons.  The default base year qdev property
     * was set to 2000 for most machine types before the century byte was
     * implemented.
     *
     * This if statement means that the century byte will be always 0
     * (at least until 2079...) for base_year = 1980, but will be set
     * correctly for base_year = 2000.
     */
    if (s->base_year == 2000) {
        s->base_year = 0;
    }

    rtc_set_date_from_host(isadev);

    switch (s->lost_tick_policy) {
#ifdef TARGET_I386
    case LOST_TICK_POLICY_SLEW:
        s->coalesced_timer =
            timer_new_ns(rtc_clock, rtc_coalesced_timer, s);
        break;
#endif
    case LOST_TICK_POLICY_DISCARD:
        break;
    default:
        error_setg(errp, "Invalid lost tick policy.");
        return;
    }

    s->periodic_timer = timer_new_ns(rtc_clock, rtc_periodic_timer, s);
    s->update_timer = timer_new_ns(rtc_clock, rtc_update_timer, s);
    check_update_timer(s);

    s->clock_reset_notifier.notify = rtc_notify_clock_reset;
    qemu_clock_register_reset_notifier(rtc_clock,
                                       &s->clock_reset_notifier);

    s->suspend_notifier.notify = rtc_notify_suspend;
    qemu_register_suspend_notifier(&s->suspend_notifier);

    memory_region_init_io(&s->io, OBJECT(s), &cmos_ops, s, "rtc", 2);
    isa_register_ioport(isadev, &s->io, base);

    /* register rtc 0x70 port for coalesced_pio */
    memory_region_set_flush_coalesced(&s->io);
    memory_region_init_io(&s->coalesced_io, OBJECT(s), &cmos_ops,
                          s, "rtc-index", 1);
    memory_region_add_subregion(&s->io, 0, &s->coalesced_io);
    memory_region_add_coalescing(&s->coalesced_io, 0, 1);

    qdev_set_legacy_instance_id(dev, base, 3);
    qemu_register_reset(rtc_reset, s);

    object_property_add_tm(OBJECT(s), "date", rtc_get_date, NULL);

    qdev_init_gpio_out(dev, &s->irq, 1);
}

ISADevice *mc146818_rtc_init(ISABus *bus, int base_year, qemu_irq intercept_irq)
{
    DeviceState *dev;
    ISADevice *isadev;
    RTCState *s;

    isadev = isa_create(bus, TYPE_MC146818_RTC);
    dev = DEVICE(isadev);
    s = MC146818_RTC(isadev);
    qdev_prop_set_int32(dev, "base_year", base_year);
    qdev_init_nofail(dev);
    if (intercept_irq) {
        qdev_connect_gpio_out(dev, 0, intercept_irq);
    } else {
        isa_connect_gpio_out(isadev, 0, RTC_ISA_IRQ);
    }
    QLIST_INSERT_HEAD(&rtc_devices, s, link);

    object_property_add_alias(qdev_get_machine(), "rtc-time", OBJECT(s),
                              "date", NULL);

    return isadev;
}

static Property mc146818rtc_properties[] = {
    DEFINE_PROP_INT32("base_year", RTCState, base_year, 1980),
    DEFINE_PROP_LOSTTICKPOLICY("lost_tick_policy", RTCState,
                               lost_tick_policy, LOST_TICK_POLICY_DISCARD),
    DEFINE_PROP_END_OF_LIST(),
};

static void rtc_resetdev(DeviceState *d)
{
    RTCState *s = MC146818_RTC(d);

    /* Reason: VM do suspend self will set 0xfe
     * Reset any values other than 0xfe(Guest suspend case) */
    if (s->cmos_data[0x0f] != 0xfe) {
        s->cmos_data[0x0f] = 0x00;
    }
}

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

    dc->realize = rtc_realizefn;
    dc->reset = rtc_resetdev;
    dc->vmsd = &vmstate_rtc;
    dc->props = mc146818rtc_properties;
    /* Reason: needs to be wired up by rtc_init() */
    dc->user_creatable = false;
}

static const TypeInfo mc146818rtc_info = {
    .name          = TYPE_MC146818_RTC,
    .parent        = TYPE_ISA_DEVICE,
    .instance_size = sizeof(RTCState),
    .class_init    = rtc_class_initfn,
};

static void mc146818rtc_register_types(void)
{
    type_register_static(&mc146818rtc_info);
}

type_init(mc146818rtc_register_types)