hw/timer/nrf51_timer.c - qemu - Git at Google

 /*
  * nRF51 System-on-Chip Timer peripheral
  *
  * Reference Manual: http://infocenter.nordicsemi.com/pdf/nRF51_RM_v3.0.pdf
  * Product Spec: http://infocenter.nordicsemi.com/pdf/nRF51822_PS_v3.1.pdf
  *
  * Copyright 2018 Steffen Görtz <contrib@steffen-goertz.de>
  * Copyright (c) 2019 Red Hat, Inc.
  *
  * This code is licensed under the GPL version 2 or later.  See
  * the COPYING file in the top-level directory.
  */

 #include "qemu/osdep.h"
 #include "qemu/log.h"
 #include "qemu/module.h"
 #include "hw/arm/nrf51.h"
 #include "hw/irq.h"
 #include "hw/timer/nrf51_timer.h"
 #include "hw/qdev-properties.h"
 #include "migration/vmstate.h"
 #include "trace.h"

 #define TIMER_CLK_FREQ 16000000UL

 static uint32_t const bitwidths[] = {16, 8, 24, 32};

 static uint32_t ns_to_ticks(NRF51TimerState *s, int64_t ns)
 {
     uint32_t freq = TIMER_CLK_FREQ >> s->prescaler;

     return muldiv64(ns, freq, NANOSECONDS_PER_SECOND);
 }

 static int64_t ticks_to_ns(NRF51TimerState *s, uint32_t ticks)
 {
     uint32_t freq = TIMER_CLK_FREQ >> s->prescaler;

     return muldiv64(ticks, NANOSECONDS_PER_SECOND, freq);
 }

 /* Returns number of ticks since last call */
 static uint32_t update_counter(NRF51TimerState *s, int64_t now)
 {
     uint32_t ticks = ns_to_ticks(s, now - s->update_counter_ns);

     s->counter = (s->counter + ticks) % BIT(bitwidths[s->bitmode]);
     /*
      * Only advance the sync time to the timestamp of the last tick,
      * not all the way to 'now', so we don't lose time if we do
      * multiple resyncs in a single tick.
      */
     s->update_counter_ns += ticks_to_ns(s, ticks);
     return ticks;
 }

 /* Assumes s->counter is up-to-date */
 static void rearm_timer(NRF51TimerState *s, int64_t now)
 {
     int64_t min_ns = INT64_MAX;
     size_t i;

     for (i = 0; i < NRF51_TIMER_REG_COUNT; i++) {
         int64_t delta_ns;

         if (s->events_compare[i]) {
             continue; /* already expired, ignore it for now */
         }

         if (s->cc[i] <= s->counter) {
             delta_ns = ticks_to_ns(s, BIT(bitwidths[s->bitmode]) -
                                       s->counter + s->cc[i]);
         } else {
             delta_ns = ticks_to_ns(s, s->cc[i] - s->counter);
         }

         if (delta_ns < min_ns) {
             min_ns = delta_ns;
         }
     }

     if (min_ns != INT64_MAX) {
         timer_mod_ns(&s->timer, now + min_ns);
     }
 }

 static void update_irq(NRF51TimerState *s)
 {
     bool flag = false;
     size_t i;

     for (i = 0; i < NRF51_TIMER_REG_COUNT; i++) {
         flag |= s->events_compare[i] && extract32(s->inten, 16 + i, 1);
     }
     qemu_set_irq(s->irq, flag);
 }

 static void timer_expire(void *opaque)
 {
     NRF51TimerState *s = NRF51_TIMER(opaque);
     int64_t now = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL);
     uint32_t cc_remaining[NRF51_TIMER_REG_COUNT];
     bool should_stop = false;
     uint32_t ticks;
     size_t i;

     for (i = 0; i < NRF51_TIMER_REG_COUNT; i++) {
         if (s->cc[i] > s->counter) {
             cc_remaining[i] = s->cc[i] - s->counter;
         } else {
             cc_remaining[i] = BIT(bitwidths[s->bitmode]) -
                               s->counter + s->cc[i];
         }
     }

     ticks = update_counter(s, now);

     for (i = 0; i < NRF51_TIMER_REG_COUNT; i++) {
         if (cc_remaining[i] <= ticks) {
             s->events_compare[i] = 1;

             if (s->shorts & BIT(i)) {
                 s->timer_start_ns = now;
                 s->update_counter_ns = s->timer_start_ns;
                 s->counter = 0;
             }

             should_stop |= s->shorts & BIT(i + 8);
         }
     }

     update_irq(s);

     if (should_stop) {
         s->running = false;
         timer_del(&s->timer);
     } else {
         rearm_timer(s, now);
     }
 }

 static void counter_compare(NRF51TimerState *s)
 {
     uint32_t counter = s->counter;
     size_t i;

     for (i = 0; i < NRF51_TIMER_REG_COUNT; i++) {
         if (counter == s->cc[i]) {
             s->events_compare[i] = 1;

             if (s->shorts & BIT(i)) {
                 s->counter = 0;
             }
         }
     }
 }

 static uint64_t nrf51_timer_read(void *opaque, hwaddr offset, unsigned int size)
 {
     NRF51TimerState *s = NRF51_TIMER(opaque);
     uint64_t r = 0;

     switch (offset) {
     case NRF51_TIMER_EVENT_COMPARE_0 ... NRF51_TIMER_EVENT_COMPARE_3:
         r = s->events_compare[(offset - NRF51_TIMER_EVENT_COMPARE_0) / 4];
         break;
     case NRF51_TIMER_REG_SHORTS:
         r = s->shorts;
         break;
     case NRF51_TIMER_REG_INTENSET:
         r = s->inten;
         break;
     case NRF51_TIMER_REG_INTENCLR:
         r = s->inten;
         break;
     case NRF51_TIMER_REG_MODE:
         r = s->mode;
         break;
     case NRF51_TIMER_REG_BITMODE:
         r = s->bitmode;
         break;
     case NRF51_TIMER_REG_PRESCALER:
         r = s->prescaler;
         break;
     case NRF51_TIMER_REG_CC0 ... NRF51_TIMER_REG_CC3:
         r = s->cc[(offset - NRF51_TIMER_REG_CC0) / 4];
         break;
     default:
         qemu_log_mask(LOG_GUEST_ERROR,
                 "%s: bad read offset 0x%" HWADDR_PRIx "\n",
                       __func__, offset);
     }

     trace_nrf51_timer_read(s->id, offset, r, size);

     return r;
 }

 static void nrf51_timer_write(void *opaque, hwaddr offset,
                        uint64_t value, unsigned int size)
 {
     NRF51TimerState *s = NRF51_TIMER(opaque);
     uint64_t now = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL);
     size_t idx;

     trace_nrf51_timer_write(s->id, offset, value, size);

     switch (offset) {
     case NRF51_TIMER_TASK_START:
         if (value == NRF51_TRIGGER_TASK && s->mode == NRF51_TIMER_TIMER) {
             s->running = true;
             s->timer_start_ns = now - ticks_to_ns(s, s->counter);
             s->update_counter_ns = s->timer_start_ns;
             rearm_timer(s, now);
         }
         break;
     case NRF51_TIMER_TASK_STOP:
     case NRF51_TIMER_TASK_SHUTDOWN:
         if (value == NRF51_TRIGGER_TASK) {
             s->running = false;
             timer_del(&s->timer);
         }
         break;
     case NRF51_TIMER_TASK_COUNT:
         if (value == NRF51_TRIGGER_TASK && s->mode == NRF51_TIMER_COUNTER) {
             s->counter = (s->counter + 1) % BIT(bitwidths[s->bitmode]);
             counter_compare(s);
         }
         break;
     case NRF51_TIMER_TASK_CLEAR:
         if (value == NRF51_TRIGGER_TASK) {
             s->timer_start_ns = now;
             s->update_counter_ns = s->timer_start_ns;
             s->counter = 0;
             if (s->running) {
                 rearm_timer(s, now);
             }
         }
         break;
     case NRF51_TIMER_TASK_CAPTURE_0 ... NRF51_TIMER_TASK_CAPTURE_3:
         if (value == NRF51_TRIGGER_TASK) {
             if (s->running) {
                 timer_expire(s); /* update counter and all state */
             }

             idx = (offset - NRF51_TIMER_TASK_CAPTURE_0) / 4;
             s->cc[idx] = s->counter;
             trace_nrf51_timer_set_count(s->id, idx, s->counter);
         }
         break;
     case NRF51_TIMER_EVENT_COMPARE_0 ... NRF51_TIMER_EVENT_COMPARE_3:
         if (value == NRF51_EVENT_CLEAR) {
             s->events_compare[(offset - NRF51_TIMER_EVENT_COMPARE_0) / 4] = 0;

             if (s->running) {
                 timer_expire(s); /* update counter and all state */
             }
         }
         break;
     case NRF51_TIMER_REG_SHORTS:
         s->shorts = value & NRF51_TIMER_REG_SHORTS_MASK;
         break;
     case NRF51_TIMER_REG_INTENSET:
         s->inten |= value & NRF51_TIMER_REG_INTEN_MASK;
         break;
     case NRF51_TIMER_REG_INTENCLR:
         s->inten &= ~(value & NRF51_TIMER_REG_INTEN_MASK);
         break;
     case NRF51_TIMER_REG_MODE:
         s->mode = value;
         break;
     case NRF51_TIMER_REG_BITMODE:
         if (s->mode == NRF51_TIMER_TIMER && s->running) {
             qemu_log_mask(LOG_GUEST_ERROR,
                     "%s: erroneous change of BITMODE while timer is running\n",
                     __func__);
         }
         s->bitmode = value & NRF51_TIMER_REG_BITMODE_MASK;
         break;
     case NRF51_TIMER_REG_PRESCALER:
         if (s->mode == NRF51_TIMER_TIMER && s->running) {
             qemu_log_mask(LOG_GUEST_ERROR,
                 "%s: erroneous change of PRESCALER while timer is running\n",
                 __func__);
         }
         s->prescaler = value & NRF51_TIMER_REG_PRESCALER_MASK;
         break;
     case NRF51_TIMER_REG_CC0 ... NRF51_TIMER_REG_CC3:
         if (s->running) {
             timer_expire(s); /* update counter */
         }

         idx = (offset - NRF51_TIMER_REG_CC0) / 4;
         s->cc[idx] = value % BIT(bitwidths[s->bitmode]);

         if (s->running) {
             rearm_timer(s, now);
         }
         break;
     default:
         qemu_log_mask(LOG_GUEST_ERROR,
                       "%s: bad write offset 0x%" HWADDR_PRIx "\n",
                       __func__, offset);
     }

     update_irq(s);
 }

 static const MemoryRegionOps rng_ops = {
     .read =  nrf51_timer_read,
     .write = nrf51_timer_write,
     .endianness = DEVICE_LITTLE_ENDIAN,
     .impl.min_access_size = 4,
     .impl.max_access_size = 4,
 };

 static void nrf51_timer_init(Object *obj)
 {
     NRF51TimerState *s = NRF51_TIMER(obj);
     SysBusDevice *sbd = SYS_BUS_DEVICE(obj);

     memory_region_init_io(&s->iomem, obj, &rng_ops, s,
                           TYPE_NRF51_TIMER, NRF51_PERIPHERAL_SIZE);
     sysbus_init_mmio(sbd, &s->iomem);
     sysbus_init_irq(sbd, &s->irq);

     timer_init_ns(&s->timer, QEMU_CLOCK_VIRTUAL, timer_expire, s);
 }

 static void nrf51_timer_reset(DeviceState *dev)
 {
     NRF51TimerState *s = NRF51_TIMER(dev);

     timer_del(&s->timer);
     s->timer_start_ns = 0x00;
     s->update_counter_ns = 0x00;
     s->counter = 0x00;
     s->running = false;

     memset(s->events_compare, 0x00, sizeof(s->events_compare));
     memset(s->cc, 0x00, sizeof(s->cc));

     s->shorts = 0x00;
     s->inten = 0x00;
     s->mode = 0x00;
     s->bitmode = 0x00;
     s->prescaler = 0x00;
 }

 static int nrf51_timer_post_load(void *opaque, int version_id)
 {
     NRF51TimerState *s = NRF51_TIMER(opaque);

     if (s->running && s->mode == NRF51_TIMER_TIMER) {
         timer_expire(s);
     }
     return 0;
 }

 static const VMStateDescription vmstate_nrf51_timer = {
     .name = TYPE_NRF51_TIMER,
     .version_id = 1,
     .post_load = nrf51_timer_post_load,
     .fields = (VMStateField[]) {
         VMSTATE_TIMER(timer, NRF51TimerState),
         VMSTATE_INT64(timer_start_ns, NRF51TimerState),
         VMSTATE_INT64(update_counter_ns, NRF51TimerState),
         VMSTATE_UINT32(counter, NRF51TimerState),
         VMSTATE_BOOL(running, NRF51TimerState),
         VMSTATE_UINT8_ARRAY(events_compare, NRF51TimerState,
                             NRF51_TIMER_REG_COUNT),
         VMSTATE_UINT32_ARRAY(cc, NRF51TimerState, NRF51_TIMER_REG_COUNT),
         VMSTATE_UINT32(shorts, NRF51TimerState),
         VMSTATE_UINT32(inten, NRF51TimerState),
         VMSTATE_UINT32(mode, NRF51TimerState),
         VMSTATE_UINT32(bitmode, NRF51TimerState),
         VMSTATE_UINT32(prescaler, NRF51TimerState),
         VMSTATE_END_OF_LIST()
     }
 };

 static Property nrf51_timer_properties[] = {
     DEFINE_PROP_UINT8("id", NRF51TimerState, id, 0),
     DEFINE_PROP_END_OF_LIST(),
 };

 static void nrf51_timer_class_init(ObjectClass *klass, void *data)
 {
     DeviceClass *dc = DEVICE_CLASS(klass);

     dc->reset = nrf51_timer_reset;
     dc->vmsd = &vmstate_nrf51_timer;
     device_class_set_props(dc, nrf51_timer_properties);
 }

 static const TypeInfo nrf51_timer_info = {
     .name = TYPE_NRF51_TIMER,
     .parent = TYPE_SYS_BUS_DEVICE,
     .instance_size = sizeof(NRF51TimerState),
     .instance_init = nrf51_timer_init,
     .class_init = nrf51_timer_class_init
 };

 static void nrf51_timer_register_types(void)
 {
     type_register_static(&nrf51_timer_info);
 }

 type_init(nrf51_timer_register_types)
	/*
	* nRF51 System-on-Chip Timer peripheral
	*
	* Reference Manual: http://infocenter.nordicsemi.com/pdf/nRF51_RM_v3.0.pdf
	* Product Spec: http://infocenter.nordicsemi.com/pdf/nRF51822_PS_v3.1.pdf
	*
	* Copyright 2018 Steffen Görtz <contrib@steffen-goertz.de>
	* Copyright (c) 2019 Red Hat, Inc.
	*
	* This code is licensed under the GPL version 2 or later. See
	* the COPYING file in the top-level directory.
	*/

	#include "qemu/osdep.h"
	#include "qemu/log.h"
	#include "qemu/module.h"
	#include "hw/arm/nrf51.h"
	#include "hw/irq.h"
	#include "hw/timer/nrf51_timer.h"
	#include "hw/qdev-properties.h"
	#include "migration/vmstate.h"
	#include "trace.h"

	#define TIMER_CLK_FREQ 16000000UL

	static uint32_t const bitwidths[] = {16, 8, 24, 32};

	static uint32_t ns_to_ticks(NRF51TimerState *s, int64_t ns)
	{
	uint32_t freq = TIMER_CLK_FREQ >> s->prescaler;

	return muldiv64(ns, freq, NANOSECONDS_PER_SECOND);
	}

	static int64_t ticks_to_ns(NRF51TimerState *s, uint32_t ticks)
	{
	uint32_t freq = TIMER_CLK_FREQ >> s->prescaler;

	return muldiv64(ticks, NANOSECONDS_PER_SECOND, freq);
	}

	/* Returns number of ticks since last call */
	static uint32_t update_counter(NRF51TimerState *s, int64_t now)
	{
	uint32_t ticks = ns_to_ticks(s, now - s->update_counter_ns);

	s->counter = (s->counter + ticks) % BIT(bitwidths[s->bitmode]);
	/*
	* Only advance the sync time to the timestamp of the last tick,
	* not all the way to 'now', so we don't lose time if we do
	* multiple resyncs in a single tick.
	*/
	s->update_counter_ns += ticks_to_ns(s, ticks);
	return ticks;
	}

	/* Assumes s->counter is up-to-date */
	static void rearm_timer(NRF51TimerState *s, int64_t now)
	{
	int64_t min_ns = INT64_MAX;
	size_t i;

	for (i = 0; i < NRF51_TIMER_REG_COUNT; i++) {
	int64_t delta_ns;

	if (s->events_compare[i]) {
	continue; /* already expired, ignore it for now */
	}

	if (s->cc[i] <= s->counter) {
	delta_ns = ticks_to_ns(s, BIT(bitwidths[s->bitmode]) -
	s->counter + s->cc[i]);
	} else {
	delta_ns = ticks_to_ns(s, s->cc[i] - s->counter);
	}

	if (delta_ns < min_ns) {
	min_ns = delta_ns;
	}
	}

	if (min_ns != INT64_MAX) {
	timer_mod_ns(&s->timer, now + min_ns);
	}
	}

	static void update_irq(NRF51TimerState *s)
	{
	bool flag = false;
	size_t i;

	for (i = 0; i < NRF51_TIMER_REG_COUNT; i++) {
	flag \|= s->events_compare[i] && extract32(s->inten, 16 + i, 1);
	}
	qemu_set_irq(s->irq, flag);
	}

	static void timer_expire(void *opaque)
	{
	NRF51TimerState *s = NRF51_TIMER(opaque);
	int64_t now = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL);
	uint32_t cc_remaining[NRF51_TIMER_REG_COUNT];
	bool should_stop = false;
	uint32_t ticks;
	size_t i;

	for (i = 0; i < NRF51_TIMER_REG_COUNT; i++) {
	if (s->cc[i] > s->counter) {
	cc_remaining[i] = s->cc[i] - s->counter;
	} else {
	cc_remaining[i] = BIT(bitwidths[s->bitmode]) -
	s->counter + s->cc[i];
	}
	}

	ticks = update_counter(s, now);

	for (i = 0; i < NRF51_TIMER_REG_COUNT; i++) {
	if (cc_remaining[i] <= ticks) {
	s->events_compare[i] = 1;

	if (s->shorts & BIT(i)) {
	s->timer_start_ns = now;
	s->update_counter_ns = s->timer_start_ns;
	s->counter = 0;
	}

	should_stop \|= s->shorts & BIT(i + 8);
	}
	}

	update_irq(s);

	if (should_stop) {
	s->running = false;
	timer_del(&s->timer);
	} else {
	rearm_timer(s, now);
	}
	}

	static void counter_compare(NRF51TimerState *s)
	{
	uint32_t counter = s->counter;
	size_t i;

	for (i = 0; i < NRF51_TIMER_REG_COUNT; i++) {
	if (counter == s->cc[i]) {
	s->events_compare[i] = 1;

	if (s->shorts & BIT(i)) {
	s->counter = 0;
	}
	}
	}
	}

	static uint64_t nrf51_timer_read(void *opaque, hwaddr offset, unsigned int size)
	{
	NRF51TimerState *s = NRF51_TIMER(opaque);
	uint64_t r = 0;

	switch (offset) {
	case NRF51_TIMER_EVENT_COMPARE_0 ... NRF51_TIMER_EVENT_COMPARE_3:
	r = s->events_compare[(offset - NRF51_TIMER_EVENT_COMPARE_0) / 4];
	break;
	case NRF51_TIMER_REG_SHORTS:
	r = s->shorts;
	break;
	case NRF51_TIMER_REG_INTENSET:
	r = s->inten;
	break;
	case NRF51_TIMER_REG_INTENCLR:
	r = s->inten;
	break;
	case NRF51_TIMER_REG_MODE:
	r = s->mode;
	break;
	case NRF51_TIMER_REG_BITMODE:
	r = s->bitmode;
	break;
	case NRF51_TIMER_REG_PRESCALER:
	r = s->prescaler;
	break;
	case NRF51_TIMER_REG_CC0 ... NRF51_TIMER_REG_CC3:
	r = s->cc[(offset - NRF51_TIMER_REG_CC0) / 4];
	break;
	default:
	qemu_log_mask(LOG_GUEST_ERROR,
	"%s: bad read offset 0x%" HWADDR_PRIx "\n",
	__func__, offset);
	}

	trace_nrf51_timer_read(s->id, offset, r, size);

	return r;
	}

	static void nrf51_timer_write(void *opaque, hwaddr offset,
	uint64_t value, unsigned int size)
	{
	NRF51TimerState *s = NRF51_TIMER(opaque);
	uint64_t now = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL);
	size_t idx;

	trace_nrf51_timer_write(s->id, offset, value, size);

	switch (offset) {
	case NRF51_TIMER_TASK_START:
	if (value == NRF51_TRIGGER_TASK && s->mode == NRF51_TIMER_TIMER) {
	s->running = true;
	s->timer_start_ns = now - ticks_to_ns(s, s->counter);
	s->update_counter_ns = s->timer_start_ns;
	rearm_timer(s, now);
	}
	break;
	case NRF51_TIMER_TASK_STOP:
	case NRF51_TIMER_TASK_SHUTDOWN:
	if (value == NRF51_TRIGGER_TASK) {
	s->running = false;
	timer_del(&s->timer);
	}
	break;
	case NRF51_TIMER_TASK_COUNT:
	if (value == NRF51_TRIGGER_TASK && s->mode == NRF51_TIMER_COUNTER) {
	s->counter = (s->counter + 1) % BIT(bitwidths[s->bitmode]);
	counter_compare(s);
	}
	break;
	case NRF51_TIMER_TASK_CLEAR:
	if (value == NRF51_TRIGGER_TASK) {
	s->timer_start_ns = now;
	s->update_counter_ns = s->timer_start_ns;
	s->counter = 0;
	if (s->running) {
	rearm_timer(s, now);
	}
	}
	break;
	case NRF51_TIMER_TASK_CAPTURE_0 ... NRF51_TIMER_TASK_CAPTURE_3:
	if (value == NRF51_TRIGGER_TASK) {
	if (s->running) {
	timer_expire(s); /* update counter and all state */
	}

	idx = (offset - NRF51_TIMER_TASK_CAPTURE_0) / 4;
	s->cc[idx] = s->counter;
	trace_nrf51_timer_set_count(s->id, idx, s->counter);
	}
	break;
	case NRF51_TIMER_EVENT_COMPARE_0 ... NRF51_TIMER_EVENT_COMPARE_3:
	if (value == NRF51_EVENT_CLEAR) {
	s->events_compare[(offset - NRF51_TIMER_EVENT_COMPARE_0) / 4] = 0;

	if (s->running) {
	timer_expire(s); /* update counter and all state */
	}
	}
	break;
	case NRF51_TIMER_REG_SHORTS:
	s->shorts = value & NRF51_TIMER_REG_SHORTS_MASK;
	break;
	case NRF51_TIMER_REG_INTENSET:
	s->inten \|= value & NRF51_TIMER_REG_INTEN_MASK;
	break;
	case NRF51_TIMER_REG_INTENCLR:
	s->inten &= ~(value & NRF51_TIMER_REG_INTEN_MASK);
	break;
	case NRF51_TIMER_REG_MODE:
	s->mode = value;
	break;
	case NRF51_TIMER_REG_BITMODE:
	if (s->mode == NRF51_TIMER_TIMER && s->running) {
	qemu_log_mask(LOG_GUEST_ERROR,
	"%s: erroneous change of BITMODE while timer is running\n",
	__func__);
	}
	s->bitmode = value & NRF51_TIMER_REG_BITMODE_MASK;
	break;
	case NRF51_TIMER_REG_PRESCALER:
	if (s->mode == NRF51_TIMER_TIMER && s->running) {
	qemu_log_mask(LOG_GUEST_ERROR,
	"%s: erroneous change of PRESCALER while timer is running\n",
	__func__);
	}
	s->prescaler = value & NRF51_TIMER_REG_PRESCALER_MASK;
	break;
	case NRF51_TIMER_REG_CC0 ... NRF51_TIMER_REG_CC3:
	if (s->running) {
	timer_expire(s); /* update counter */
	}

	idx = (offset - NRF51_TIMER_REG_CC0) / 4;
	s->cc[idx] = value % BIT(bitwidths[s->bitmode]);

	if (s->running) {
	rearm_timer(s, now);
	}
	break;
	default:
	qemu_log_mask(LOG_GUEST_ERROR,
	"%s: bad write offset 0x%" HWADDR_PRIx "\n",
	__func__, offset);
	}

	update_irq(s);
	}

	static const MemoryRegionOps rng_ops = {
	.read = nrf51_timer_read,
	.write = nrf51_timer_write,
	.endianness = DEVICE_LITTLE_ENDIAN,
	.impl.min_access_size = 4,
	.impl.max_access_size = 4,
	};

	static void nrf51_timer_init(Object *obj)
	{
	NRF51TimerState *s = NRF51_TIMER(obj);
	SysBusDevice *sbd = SYS_BUS_DEVICE(obj);

	memory_region_init_io(&s->iomem, obj, &rng_ops, s,
	TYPE_NRF51_TIMER, NRF51_PERIPHERAL_SIZE);
	sysbus_init_mmio(sbd, &s->iomem);
	sysbus_init_irq(sbd, &s->irq);

	timer_init_ns(&s->timer, QEMU_CLOCK_VIRTUAL, timer_expire, s);
	}

	static void nrf51_timer_reset(DeviceState *dev)
	{
	NRF51TimerState *s = NRF51_TIMER(dev);

	timer_del(&s->timer);
	s->timer_start_ns = 0x00;
	s->update_counter_ns = 0x00;
	s->counter = 0x00;
	s->running = false;

	memset(s->events_compare, 0x00, sizeof(s->events_compare));
	memset(s->cc, 0x00, sizeof(s->cc));

	s->shorts = 0x00;
	s->inten = 0x00;
	s->mode = 0x00;
	s->bitmode = 0x00;
	s->prescaler = 0x00;
	}

	static int nrf51_timer_post_load(void *opaque, int version_id)
	{
	NRF51TimerState *s = NRF51_TIMER(opaque);

	if (s->running && s->mode == NRF51_TIMER_TIMER) {
	timer_expire(s);
	}
	return 0;
	}

	static const VMStateDescription vmstate_nrf51_timer = {
	.name = TYPE_NRF51_TIMER,
	.version_id = 1,
	.post_load = nrf51_timer_post_load,
	.fields = (VMStateField[]) {
	VMSTATE_TIMER(timer, NRF51TimerState),
	VMSTATE_INT64(timer_start_ns, NRF51TimerState),
	VMSTATE_INT64(update_counter_ns, NRF51TimerState),
	VMSTATE_UINT32(counter, NRF51TimerState),
	VMSTATE_BOOL(running, NRF51TimerState),
	VMSTATE_UINT8_ARRAY(events_compare, NRF51TimerState,
	NRF51_TIMER_REG_COUNT),
	VMSTATE_UINT32_ARRAY(cc, NRF51TimerState, NRF51_TIMER_REG_COUNT),
	VMSTATE_UINT32(shorts, NRF51TimerState),
	VMSTATE_UINT32(inten, NRF51TimerState),
	VMSTATE_UINT32(mode, NRF51TimerState),
	VMSTATE_UINT32(bitmode, NRF51TimerState),
	VMSTATE_UINT32(prescaler, NRF51TimerState),
	VMSTATE_END_OF_LIST()
	}
	};

	static Property nrf51_timer_properties[] = {
	DEFINE_PROP_UINT8("id", NRF51TimerState, id, 0),
	DEFINE_PROP_END_OF_LIST(),
	};

	static void nrf51_timer_class_init(ObjectClass klass, void data)
	{
	DeviceClass *dc = DEVICE_CLASS(klass);

	dc->reset = nrf51_timer_reset;
	dc->vmsd = &vmstate_nrf51_timer;
	device_class_set_props(dc, nrf51_timer_properties);
	}

	static const TypeInfo nrf51_timer_info = {
	.name = TYPE_NRF51_TIMER,
	.parent = TYPE_SYS_BUS_DEVICE,
	.instance_size = sizeof(NRF51TimerState),
	.instance_init = nrf51_timer_init,
	.class_init = nrf51_timer_class_init
	};

	static void nrf51_timer_register_types(void)
	{
	type_register_static(&nrf51_timer_info);
	}

	type_init(nrf51_timer_register_types)