hw/timer/pl031.c

   1 /*
   2  * ARM AMBA PrimeCell PL031 RTC
   3  *
   4  * Copyright (c) 2007 CodeSourcery
   5  *
   6  * This file is free software; you can redistribute it and/or modify
   7  * it under the terms of the GNU General Public License version 2 as
   8  * published by the Free Software Foundation.
   9  *
  10  * Contributions after 2012-01-13 are licensed under the terms of the
  11  * GNU GPL, version 2 or (at your option) any later version.
  12  */
  13
  14 #include "qemu/osdep.h"
  15 #include "qemu-common.h"
  16 #include "hw/timer/pl031.h"
  17 #include "hw/sysbus.h"
  18 #include "qemu/timer.h"
  19 #include "sysemu/sysemu.h"
  20 #include "qemu/cutils.h"
  21 #include "qemu/log.h"
  22 #include "qemu/module.h"
  23 #include "trace.h"
  24
  25 #define RTC_DR      0x00    /* Data read register */
  26 #define RTC_MR      0x04    /* Match register */
  27 #define RTC_LR      0x08    /* Data load register */
  28 #define RTC_CR      0x0c    /* Control register */
  29 #define RTC_IMSC    0x10    /* Interrupt mask and set register */
  30 #define RTC_RIS     0x14    /* Raw interrupt status register */
  31 #define RTC_MIS     0x18    /* Masked interrupt status register */
  32 #define RTC_ICR     0x1c    /* Interrupt clear register */
  33
  34 static const unsigned char pl031_id[] = {
  35     0x31, 0x10, 0x14, 0x00,         /* Device ID        */
  36     0x0d, 0xf0, 0x05, 0xb1          /* Cell ID      */
  37 };
  38
  39 static void pl031_update(PL031State *s)
  40 {
  41     uint32_t flags = s->is & s->im;
  42
  43     trace_pl031_irq_state(flags);
  44     qemu_set_irq(s->irq, flags);
  45 }
  46
  47 static void pl031_interrupt(void * opaque)
  48 {
  49     PL031State *s = (PL031State *)opaque;
  50
  51     s->is = 1;
  52     trace_pl031_alarm_raised();
  53     pl031_update(s);
  54 }
  55
  56 static uint32_t pl031_get_count(PL031State *s)
  57 {
  58     int64_t now = qemu_clock_get_ns(rtc_clock);
  59     return s->tick_offset + now / NANOSECONDS_PER_SECOND;
  60 }
  61
  62 static void pl031_set_alarm(PL031State *s)
  63 {
  64     uint32_t ticks;
  65
  66     /* The timer wraps around.  This subtraction also wraps in the same way,
  67        and gives correct results when alarm < now_ticks.  */
  68     ticks = s->mr - pl031_get_count(s);
  69     trace_pl031_set_alarm(ticks);
  70     if (ticks == 0) {
  71         timer_del(s->timer);
  72         pl031_interrupt(s);
  73     } else {
  74         int64_t now = qemu_clock_get_ns(rtc_clock);
  75         timer_mod(s->timer, now + (int64_t)ticks * NANOSECONDS_PER_SECOND);
  76     }
  77 }
  78
  79 static uint64_t pl031_read(void *opaque, hwaddr offset,
  80                            unsigned size)
  81 {
  82     PL031State *s = (PL031State *)opaque;
  83     uint64_t r;
  84
  85     switch (offset) {
  86     case RTC_DR:
  87         r = pl031_get_count(s);
  88         break;
  89     case RTC_MR:
  90         r = s->mr;
  91         break;
  92     case RTC_IMSC:
  93         r = s->im;
  94         break;
  95     case RTC_RIS:
  96         r = s->is;
  97         break;
  98     case RTC_LR:
  99         r = s->lr;
 100         break;
 101     case RTC_CR:
 102         /* RTC is permanently enabled.  */
 103         r = 1;
 104         break;
 105     case RTC_MIS:
 106         r = s->is & s->im;
 107         break;
 108     case 0xfe0 ... 0xfff:
 109         r = pl031_id[(offset - 0xfe0) >> 2];
 110         break;
 111     case RTC_ICR:
 112         qemu_log_mask(LOG_GUEST_ERROR,
 113                       "pl031: read of write-only register at offset 0x%x\n",
 114                       (int)offset);
 115         r = 0;
 116         break;
 117     default:
 118         qemu_log_mask(LOG_GUEST_ERROR,
 119                       "pl031_read: Bad offset 0x%x\n", (int)offset);
 120         r = 0;
 121         break;
 122     }
 123
 124     trace_pl031_read(offset, r);
 125     return r;
 126 }
 127
 128 static void pl031_write(void * opaque, hwaddr offset,
 129                         uint64_t value, unsigned size)
 130 {
 131     PL031State *s = (PL031State *)opaque;
 132
 133     trace_pl031_write(offset, value);
 134
 135     switch (offset) {
 136     case RTC_LR:
 137         s->tick_offset += value - pl031_get_count(s);
 138         pl031_set_alarm(s);
 139         break;
 140     case RTC_MR:
 141         s->mr = value;
 142         pl031_set_alarm(s);
 143         break;
 144     case RTC_IMSC:
 145         s->im = value & 1;
 146         pl031_update(s);
 147         break;
 148     case RTC_ICR:
 149         /* The PL031 documentation (DDI0224B) states that the interrupt is
 150            cleared when bit 0 of the written value is set.  However the
 151            arm926e documentation (DDI0287B) states that the interrupt is
 152            cleared when any value is written.  */
 153         s->is = 0;
 154         pl031_update(s);
 155         break;
 156     case RTC_CR:
 157         /* Written value is ignored.  */
 158         break;
 159
 160     case RTC_DR:
 161     case RTC_MIS:
 162     case RTC_RIS:
 163         qemu_log_mask(LOG_GUEST_ERROR,
 164                       "pl031: write to read-only register at offset 0x%x\n",
 165                       (int)offset);
 166         break;
 167
 168     default:
 169         qemu_log_mask(LOG_GUEST_ERROR,
 170                       "pl031_write: Bad offset 0x%x\n", (int)offset);
 171         break;
 172     }
 173 }
 174
 175 static const MemoryRegionOps pl031_ops = {
 176     .read = pl031_read,
 177     .write = pl031_write,
 178     .endianness = DEVICE_NATIVE_ENDIAN,
 179 };
 180
 181 static void pl031_init(Object *obj)
 182 {
 183     PL031State *s = PL031(obj);
 184     SysBusDevice *dev = SYS_BUS_DEVICE(obj);
 185     struct tm tm;
 186
 187     memory_region_init_io(&s->iomem, obj, &pl031_ops, s, "pl031", 0x1000);
 188     sysbus_init_mmio(dev, &s->iomem);
 189
 190     sysbus_init_irq(dev, &s->irq);
 191     qemu_get_timedate(&tm, 0);
 192     s->tick_offset = mktimegm(&tm) -
 193         qemu_clock_get_ns(rtc_clock) / NANOSECONDS_PER_SECOND;
 194
 195     s->timer = timer_new_ns(rtc_clock, pl031_interrupt, s);
 196 }
 197
 198 static int pl031_pre_save(void *opaque)
 199 {
 200     PL031State *s = opaque;
 201
 202     /*
 203      * The PL031 device model code uses the tick_offset field, which is
 204      * the offset between what the guest RTC should read and what the
 205      * QEMU rtc_clock reads:
 206      *  guest_rtc = rtc_clock + tick_offset
 207      * and so
 208      *  tick_offset = guest_rtc - rtc_clock
 209      *
 210      * We want to migrate this offset, which sounds straightforward.
 211      * Unfortunately older versions of QEMU migrated a conversion of this
 212      * offset into an offset from the vm_clock. (This was in turn an
 213      * attempt to be compatible with even older QEMU versions, but it
 214      * has incorrect behaviour if the rtc_clock is not the same as the
 215      * vm_clock.) So we put the actual tick_offset into a migration
 216      * subsection, and the backwards-compatible time-relative-to-vm_clock
 217      * in the main migration state.
 218      *
 219      * Calculate base time relative to QEMU_CLOCK_VIRTUAL:
 220      */
 221     int64_t delta = qemu_clock_get_ns(rtc_clock) - qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL);
 222     s->tick_offset_vmstate = s->tick_offset + delta / NANOSECONDS_PER_SECOND;
 223
 224     return 0;
 225 }
 226
 227 static int pl031_pre_load(void *opaque)
 228 {
 229     PL031State *s = opaque;
 230
 231     s->tick_offset_migrated = false;
 232     return 0;
 233 }
 234
 235 static int pl031_post_load(void *opaque, int version_id)
 236 {
 237     PL031State *s = opaque;
 238
 239     /*
 240      * If we got the tick_offset subsection, then we can just use
 241      * the value in that. Otherwise the source is an older QEMU and
 242      * has given us the offset from the vm_clock; convert it back to
 243      * an offset from the rtc_clock. This will cause time to incorrectly
 244      * go backwards compared to the host RTC, but this is unavoidable.
 245      */
 246
 247     if (!s->tick_offset_migrated) {
 248         int64_t delta = qemu_clock_get_ns(rtc_clock) -
 249             qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL);
 250         s->tick_offset = s->tick_offset_vmstate -
 251             delta / NANOSECONDS_PER_SECOND;
 252     }
 253     pl031_set_alarm(s);
 254     return 0;
 255 }
 256
 257 static int pl031_tick_offset_post_load(void *opaque, int version_id)
 258 {
 259     PL031State *s = opaque;
 260
 261     s->tick_offset_migrated = true;
 262     return 0;
 263 }
 264
 265 static bool pl031_tick_offset_needed(void *opaque)
 266 {
 267     PL031State *s = opaque;
 268
 269     return s->migrate_tick_offset;
 270 }
 271
 272 static const VMStateDescription vmstate_pl031_tick_offset = {
 273     .name = "pl031/tick-offset",
 274     .version_id = 1,
 275     .minimum_version_id = 1,
 276     .needed = pl031_tick_offset_needed,
 277     .post_load = pl031_tick_offset_post_load,
 278     .fields = (VMStateField[]) {
 279         VMSTATE_UINT32(tick_offset, PL031State),
 280         VMSTATE_END_OF_LIST()
 281     }
 282 };
 283
 284 static const VMStateDescription vmstate_pl031 = {
 285     .name = "pl031",
 286     .version_id = 1,
 287     .minimum_version_id = 1,
 288     .pre_save = pl031_pre_save,
 289     .pre_load = pl031_pre_load,
 290     .post_load = pl031_post_load,
 291     .fields = (VMStateField[]) {
 292         VMSTATE_UINT32(tick_offset_vmstate, PL031State),
 293         VMSTATE_UINT32(mr, PL031State),
 294         VMSTATE_UINT32(lr, PL031State),
 295         VMSTATE_UINT32(cr, PL031State),
 296         VMSTATE_UINT32(im, PL031State),
 297         VMSTATE_UINT32(is, PL031State),
 298         VMSTATE_END_OF_LIST()
 299     },
 300     .subsections = (const VMStateDescription*[]) {
 301         &vmstate_pl031_tick_offset,
 302         NULL
 303     }
 304 };
 305
 306 static Property pl031_properties[] = {
 307     /*
 308      * True to correctly migrate the tick offset of the RTC. False to
 309      * obtain backward migration compatibility with older QEMU versions,
 310      * at the expense of the guest RTC going backwards compared with the
 311      * host RTC when the VM is saved/restored if using -rtc host.
 312      * (Even if set to 'true' older QEMU can migrate forward to newer QEMU;
 313      * 'false' also permits newer QEMU to migrate to older QEMU.)
 314      */
 315     DEFINE_PROP_BOOL("migrate-tick-offset",
 316                      PL031State, migrate_tick_offset, true),
 317     DEFINE_PROP_END_OF_LIST()
 318 };
 319
 320 static void pl031_class_init(ObjectClass *klass, void *data)
 321 {
 322     DeviceClass *dc = DEVICE_CLASS(klass);
 323
 324     dc->vmsd = &vmstate_pl031;
 325     dc->props = pl031_properties;
 326 }
 327
 328 static const TypeInfo pl031_info = {
 329     .name          = TYPE_PL031,
 330     .parent        = TYPE_SYS_BUS_DEVICE,
 331     .instance_size = sizeof(PL031State),
 332     .instance_init = pl031_init,
 333     .class_init    = pl031_class_init,
 334 };
 335
 336 static void pl031_register_types(void)
 337 {
 338     type_register_static(&pl031_info);
 339 }
 340
 341 type_init(pl031_register_types)