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 "migration/vmstate.h"
  18 #include "hw/irq.h"
  19 #include "hw/qdev-properties.h"
  20 #include "hw/sysbus.h"
  21 #include "qemu/timer.h"
  22 #include "sysemu/sysemu.h"
  23 #include "qemu/cutils.h"
  24 #include "qemu/log.h"
  25 #include "qemu/module.h"
  26 #include "trace.h"
  27
  28 #define RTC_DR      0x00    /* Data read register */
  29 #define RTC_MR      0x04    /* Match register */
  30 #define RTC_LR      0x08    /* Data load register */
  31 #define RTC_CR      0x0c    /* Control register */
  32 #define RTC_IMSC    0x10    /* Interrupt mask and set register */
  33 #define RTC_RIS     0x14    /* Raw interrupt status register */
  34 #define RTC_MIS     0x18    /* Masked interrupt status register */
  35 #define RTC_ICR     0x1c    /* Interrupt clear register */
  36
  37 static const unsigned char pl031_id[] = {
  38     0x31, 0x10, 0x14, 0x00,         /* Device ID        */
  39     0x0d, 0xf0, 0x05, 0xb1          /* Cell ID      */
  40 };
  41
  42 static void pl031_update(PL031State *s)
  43 {
  44     uint32_t flags = s->is & s->im;
  45
  46     trace_pl031_irq_state(flags);
  47     qemu_set_irq(s->irq, flags);
  48 }
  49
  50 static void pl031_interrupt(void * opaque)
  51 {
  52     PL031State *s = (PL031State *)opaque;
  53
  54     s->is = 1;
  55     trace_pl031_alarm_raised();
  56     pl031_update(s);
  57 }
  58
  59 static uint32_t pl031_get_count(PL031State *s)
  60 {
  61     int64_t now = qemu_clock_get_ns(rtc_clock);
  62     return s->tick_offset + now / NANOSECONDS_PER_SECOND;
  63 }
  64
  65 static void pl031_set_alarm(PL031State *s)
  66 {
  67     uint32_t ticks;
  68
  69     /* The timer wraps around.  This subtraction also wraps in the same way,
  70        and gives correct results when alarm < now_ticks.  */
  71     ticks = s->mr - pl031_get_count(s);
  72     trace_pl031_set_alarm(ticks);
  73     if (ticks == 0) {
  74         timer_del(s->timer);
  75         pl031_interrupt(s);
  76     } else {
  77         int64_t now = qemu_clock_get_ns(rtc_clock);
  78         timer_mod(s->timer, now + (int64_t)ticks * NANOSECONDS_PER_SECOND);
  79     }
  80 }
  81
  82 static uint64_t pl031_read(void *opaque, hwaddr offset,
  83                            unsigned size)
  84 {
  85     PL031State *s = (PL031State *)opaque;
  86     uint64_t r;
  87
  88     switch (offset) {
  89     case RTC_DR:
  90         r = pl031_get_count(s);
  91         break;
  92     case RTC_MR:
  93         r = s->mr;
  94         break;
  95     case RTC_IMSC:
  96         r = s->im;
  97         break;
  98     case RTC_RIS:
  99         r = s->is;
 100         break;
 101     case RTC_LR:
 102         r = s->lr;
 103         break;
 104     case RTC_CR:
 105         /* RTC is permanently enabled.  */
 106         r = 1;
 107         break;
 108     case RTC_MIS:
 109         r = s->is & s->im;
 110         break;
 111     case 0xfe0 ... 0xfff:
 112         r = pl031_id[(offset - 0xfe0) >> 2];
 113         break;
 114     case RTC_ICR:
 115         qemu_log_mask(LOG_GUEST_ERROR,
 116                       "pl031: read of write-only register at offset 0x%x\n",
 117                       (int)offset);
 118         r = 0;
 119         break;
 120     default:
 121         qemu_log_mask(LOG_GUEST_ERROR,
 122                       "pl031_read: Bad offset 0x%x\n", (int)offset);
 123         r = 0;
 124         break;
 125     }
 126
 127     trace_pl031_read(offset, r);
 128     return r;
 129 }
 130
 131 static void pl031_write(void * opaque, hwaddr offset,
 132                         uint64_t value, unsigned size)
 133 {
 134     PL031State *s = (PL031State *)opaque;
 135
 136     trace_pl031_write(offset, value);
 137
 138     switch (offset) {
 139     case RTC_LR:
 140         s->tick_offset += value - pl031_get_count(s);
 141         pl031_set_alarm(s);
 142         break;
 143     case RTC_MR:
 144         s->mr = value;
 145         pl031_set_alarm(s);
 146         break;
 147     case RTC_IMSC:
 148         s->im = value & 1;
 149         pl031_update(s);
 150         break;
 151     case RTC_ICR:
 152         /* The PL031 documentation (DDI0224B) states that the interrupt is
 153            cleared when bit 0 of the written value is set.  However the
 154            arm926e documentation (DDI0287B) states that the interrupt is
 155            cleared when any value is written.  */
 156         s->is = 0;
 157         pl031_update(s);
 158         break;
 159     case RTC_CR:
 160         /* Written value is ignored.  */
 161         break;
 162
 163     case RTC_DR:
 164     case RTC_MIS:
 165     case RTC_RIS:
 166         qemu_log_mask(LOG_GUEST_ERROR,
 167                       "pl031: write to read-only register at offset 0x%x\n",
 168                       (int)offset);
 169         break;
 170
 171     default:
 172         qemu_log_mask(LOG_GUEST_ERROR,
 173                       "pl031_write: Bad offset 0x%x\n", (int)offset);
 174         break;
 175     }
 176 }
 177
 178 static const MemoryRegionOps pl031_ops = {
 179     .read = pl031_read,
 180     .write = pl031_write,
 181     .endianness = DEVICE_NATIVE_ENDIAN,
 182 };
 183
 184 static void pl031_init(Object *obj)
 185 {
 186     PL031State *s = PL031(obj);
 187     SysBusDevice *dev = SYS_BUS_DEVICE(obj);
 188     struct tm tm;
 189
 190     memory_region_init_io(&s->iomem, obj, &pl031_ops, s, "pl031", 0x1000);
 191     sysbus_init_mmio(dev, &s->iomem);
 192
 193     sysbus_init_irq(dev, &s->irq);
 194     qemu_get_timedate(&tm, 0);
 195     s->tick_offset = mktimegm(&tm) -
 196         qemu_clock_get_ns(rtc_clock) / NANOSECONDS_PER_SECOND;
 197
 198     s->timer = timer_new_ns(rtc_clock, pl031_interrupt, s);
 199 }
 200
 201 static int pl031_pre_save(void *opaque)
 202 {
 203     PL031State *s = opaque;
 204
 205     /*
 206      * The PL031 device model code uses the tick_offset field, which is
 207      * the offset between what the guest RTC should read and what the
 208      * QEMU rtc_clock reads:
 209      *  guest_rtc = rtc_clock + tick_offset
 210      * and so
 211      *  tick_offset = guest_rtc - rtc_clock
 212      *
 213      * We want to migrate this offset, which sounds straightforward.
 214      * Unfortunately older versions of QEMU migrated a conversion of this
 215      * offset into an offset from the vm_clock. (This was in turn an
 216      * attempt to be compatible with even older QEMU versions, but it
 217      * has incorrect behaviour if the rtc_clock is not the same as the
 218      * vm_clock.) So we put the actual tick_offset into a migration
 219      * subsection, and the backwards-compatible time-relative-to-vm_clock
 220      * in the main migration state.
 221      *
 222      * Calculate base time relative to QEMU_CLOCK_VIRTUAL:
 223      */
 224     int64_t delta = qemu_clock_get_ns(rtc_clock) - qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL);
 225     s->tick_offset_vmstate = s->tick_offset + delta / NANOSECONDS_PER_SECOND;
 226
 227     return 0;
 228 }
 229
 230 static int pl031_pre_load(void *opaque)
 231 {
 232     PL031State *s = opaque;
 233
 234     s->tick_offset_migrated = false;
 235     return 0;
 236 }
 237
 238 static int pl031_post_load(void *opaque, int version_id)
 239 {
 240     PL031State *s = opaque;
 241
 242     /*
 243      * If we got the tick_offset subsection, then we can just use
 244      * the value in that. Otherwise the source is an older QEMU and
 245      * has given us the offset from the vm_clock; convert it back to
 246      * an offset from the rtc_clock. This will cause time to incorrectly
 247      * go backwards compared to the host RTC, but this is unavoidable.
 248      */
 249
 250     if (!s->tick_offset_migrated) {
 251         int64_t delta = qemu_clock_get_ns(rtc_clock) -
 252             qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL);
 253         s->tick_offset = s->tick_offset_vmstate -
 254             delta / NANOSECONDS_PER_SECOND;
 255     }
 256     pl031_set_alarm(s);
 257     return 0;
 258 }
 259
 260 static int pl031_tick_offset_post_load(void *opaque, int version_id)
 261 {
 262     PL031State *s = opaque;
 263
 264     s->tick_offset_migrated = true;
 265     return 0;
 266 }
 267
 268 static bool pl031_tick_offset_needed(void *opaque)
 269 {
 270     PL031State *s = opaque;
 271
 272     return s->migrate_tick_offset;
 273 }
 274
 275 static const VMStateDescription vmstate_pl031_tick_offset = {
 276     .name = "pl031/tick-offset",
 277     .version_id = 1,
 278     .minimum_version_id = 1,
 279     .needed = pl031_tick_offset_needed,
 280     .post_load = pl031_tick_offset_post_load,
 281     .fields = (VMStateField[]) {
 282         VMSTATE_UINT32(tick_offset, PL031State),
 283         VMSTATE_END_OF_LIST()
 284     }
 285 };
 286
 287 static const VMStateDescription vmstate_pl031 = {
 288     .name = "pl031",
 289     .version_id = 1,
 290     .minimum_version_id = 1,
 291     .pre_save = pl031_pre_save,
 292     .pre_load = pl031_pre_load,
 293     .post_load = pl031_post_load,
 294     .fields = (VMStateField[]) {
 295         VMSTATE_UINT32(tick_offset_vmstate, PL031State),
 296         VMSTATE_UINT32(mr, PL031State),
 297         VMSTATE_UINT32(lr, PL031State),
 298         VMSTATE_UINT32(cr, PL031State),
 299         VMSTATE_UINT32(im, PL031State),
 300         VMSTATE_UINT32(is, PL031State),
 301         VMSTATE_END_OF_LIST()
 302     },
 303     .subsections = (const VMStateDescription*[]) {
 304         &vmstate_pl031_tick_offset,
 305         NULL
 306     }
 307 };
 308
 309 static Property pl031_properties[] = {
 310     /*
 311      * True to correctly migrate the tick offset of the RTC. False to
 312      * obtain backward migration compatibility with older QEMU versions,
 313      * at the expense of the guest RTC going backwards compared with the
 314      * host RTC when the VM is saved/restored if using -rtc host.
 315      * (Even if set to 'true' older QEMU can migrate forward to newer QEMU;
 316      * 'false' also permits newer QEMU to migrate to older QEMU.)
 317      */
 318     DEFINE_PROP_BOOL("migrate-tick-offset",
 319                      PL031State, migrate_tick_offset, true),
 320     DEFINE_PROP_END_OF_LIST()
 321 };
 322
 323 static void pl031_class_init(ObjectClass *klass, void *data)
 324 {
 325     DeviceClass *dc = DEVICE_CLASS(klass);
 326
 327     dc->vmsd = &vmstate_pl031;
 328     dc->props = pl031_properties;
 329 }
 330
 331 static const TypeInfo pl031_info = {
 332     .name          = TYPE_PL031,
 333     .parent        = TYPE_SYS_BUS_DEVICE,
 334     .instance_size = sizeof(PL031State),
 335     .instance_init = pl031_init,
 336     .class_init    = pl031_class_init,
 337 };
 338
 339 static void pl031_register_types(void)
 340 {
 341     type_register_static(&pl031_info);
 342 }
 343
 344 type_init(pl031_register_types)