hw/timer/hpet.c - qemu - Git at Google

 /*
  *  High Precision 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 "qemu/osdep.h"
 #include "hw/hw.h"
 #include "hw/i386/pc.h"
 #include "ui/console.h"
 #include "qapi/error.h"
 #include "qemu/error-report.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 - a) < 0);
 }

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

 static uint64_t ticks_to_ns(uint64_t value)
 {
     return value * HPET_CLK_PERIOD;
 }

 static uint64_t ns_to_ticks(uint64_t value)
 {
     return value / 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)) {
             qemu_irq_lower(s->irqs[route]);
         }
     } else if (timer_fsb_route(timer)) {
         address_space_stl_le(&address_space_memory, timer->fsb >> 32,
                              timer->fsb & 0xffffffff, MEMTXATTRS_UNSPECIFIED,
                              NULL);
     } else if (timer->config & HPET_TN_TYPE_LEVEL) {
         s->isr |= mask;
         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,
     .needed = hpet_rtc_irq_level_needed,
     .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,
     .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_PTR(qemu_timer, HPETTimer),
         VMSTATE_END_OF_LIST()
     }
 };

 static const VMStateDescription vmstate_hpet = {
     .name = "hpet",
     .version_id = 2,
     .minimum_version_id = 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 = (const VMStateDescription*[]) {
         &vmstate_hpet_rtc_irq_level,
         NULL
     }
 };

 /*
  * 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", HPET_LEN);
     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 |= ((uint64_t)(HPET_CLK_PERIOD * FS_PER_NS) << 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)
	/*
	* High Precision 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 "qemu/osdep.h"
	#include "hw/hw.h"
	#include "hw/i386/pc.h"
	#include "ui/console.h"
	#include "qapi/error.h"
	#include "qemu/error-report.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 - a) < 0);
	}

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

	static uint64_t ticks_to_ns(uint64_t value)
	{
	return value * HPET_CLK_PERIOD;
	}

	static uint64_t ns_to_ticks(uint64_t value)
	{
	return value / 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)) {
	qemu_irq_lower(s->irqs[route]);
	}
	} else if (timer_fsb_route(timer)) {
	address_space_stl_le(&address_space_memory, timer->fsb >> 32,
	timer->fsb & 0xffffffff, MEMTXATTRS_UNSPECIFIED,
	NULL);
	} else if (timer->config & HPET_TN_TYPE_LEVEL) {
	s->isr \|= mask;
	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,
	.needed = hpet_rtc_irq_level_needed,
	.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,
	.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_PTR(qemu_timer, HPETTimer),
	VMSTATE_END_OF_LIST()
	}
	};

	static const VMStateDescription vmstate_hpet = {
	.name = "hpet",
	.version_id = 2,
	.minimum_version_id = 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 = (const VMStateDescription*[]) {
	&vmstate_hpet_rtc_irq_level,
	NULL
	}
	};

	/*
	* 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", HPET_LEN);
	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 \|= ((uint64_t)(HPET_CLK_PERIOD * FS_PER_NS) << 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)