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

 /*
  * IMX EPIT Timer
  *
  * Copyright (c) 2008 OK Labs
  * Copyright (c) 2011 NICTA Pty Ltd
  * Originally written by Hans Jiang
  * Updated by Peter Chubb
  * Updated by Jean-Christophe Dubois <jcd@tribudubois.net>
  * Updated by Axel Heider
  *
  * This code is licensed under GPL version 2 or later.  See
  * the COPYING file in the top-level directory.
  *
  */

 #include "qemu/osdep.h"
 #include "hw/timer/imx_epit.h"
 #include "migration/vmstate.h"
 #include "hw/irq.h"
 #include "hw/misc/imx_ccm.h"
 #include "qemu/module.h"
 #include "qemu/log.h"

 #ifndef DEBUG_IMX_EPIT
 #define DEBUG_IMX_EPIT 0
 #endif

 #define DPRINTF(fmt, args...) \
     do { \
         if (DEBUG_IMX_EPIT) { \
             fprintf(stderr, "[%s]%s: " fmt , TYPE_IMX_EPIT, \
                                              __func__, ##args); \
         } \
     } while (0)

 static const char *imx_epit_reg_name(uint32_t reg)
 {
     switch (reg) {
     case 0:
         return "CR";
     case 1:
         return "SR";
     case 2:
         return "LR";
     case 3:
         return "CMP";
     case 4:
         return "CNT";
     default:
         return "[?]";
     }
 }

 /*
  * Exact clock frequencies vary from board to board.
  * These are typical.
  */
 static const IMXClk imx_epit_clocks[] =  {
     CLK_NONE,      /* 00 disabled */
     CLK_IPG,       /* 01 ipg_clk, ~532MHz */
     CLK_IPG_HIGH,  /* 10 ipg_clk_highfreq */
     CLK_32k,       /* 11 ipg_clk_32k -- ~32kHz */
 };

 /*
  * Update interrupt status
  */
 static void imx_epit_update_int(IMXEPITState *s)
 {
     if ((s->sr & SR_OCIF) && (s->cr & CR_OCIEN) && (s->cr & CR_EN)) {
         qemu_irq_raise(s->irq);
     } else {
         qemu_irq_lower(s->irq);
     }
 }

 static uint32_t imx_epit_get_freq(IMXEPITState *s)
 {
     uint32_t clksrc = extract32(s->cr, CR_CLKSRC_SHIFT, CR_CLKSRC_BITS);
     uint32_t prescaler = 1 + extract32(s->cr, CR_PRESCALE_SHIFT, CR_PRESCALE_BITS);
     uint32_t f_in = imx_ccm_get_clock_frequency(s->ccm, imx_epit_clocks[clksrc]);
     uint32_t freq = f_in / prescaler;
     DPRINTF("ptimer frequency is %u\n", freq);
     return freq;
 }

 /*
  * This is called both on hardware (device) reset and software reset.
  */
 static void imx_epit_reset(IMXEPITState *s, bool is_hard_reset)
 {
     /* Soft reset doesn't touch some bits; hard reset clears them */
     if (is_hard_reset) {
         s->cr = 0;
     } else {
         s->cr &= (CR_EN|CR_ENMOD|CR_STOPEN|CR_DOZEN|CR_WAITEN|CR_DBGEN);
     }
     s->sr = 0;
     s->lr = EPIT_TIMER_MAX;
     s->cmp = 0;
     ptimer_transaction_begin(s->timer_cmp);
     ptimer_transaction_begin(s->timer_reload);

     /*
      * The reset switches off the input clock, so even if the CR.EN is still
      * set, the timers are no longer running.
      */
     assert(imx_epit_get_freq(s) == 0);
     ptimer_stop(s->timer_cmp);
     ptimer_stop(s->timer_reload);
     /* init both timers to EPIT_TIMER_MAX */
     ptimer_set_limit(s->timer_cmp, EPIT_TIMER_MAX, 1);
     ptimer_set_limit(s->timer_reload, EPIT_TIMER_MAX, 1);
     ptimer_transaction_commit(s->timer_cmp);
     ptimer_transaction_commit(s->timer_reload);
 }

 static uint64_t imx_epit_read(void *opaque, hwaddr offset, unsigned size)
 {
     IMXEPITState *s = IMX_EPIT(opaque);
     uint32_t reg_value = 0;

     switch (offset >> 2) {
     case 0: /* Control Register */
         reg_value = s->cr;
         break;

     case 1: /* Status Register */
         reg_value = s->sr;
         break;

     case 2: /* LR - ticks*/
         reg_value = s->lr;
         break;

     case 3: /* CMP */
         reg_value = s->cmp;
         break;

     case 4: /* CNT */
         reg_value = ptimer_get_count(s->timer_reload);
         break;

     default:
         qemu_log_mask(LOG_GUEST_ERROR, "[%s]%s: Bad register at offset 0x%"
                       HWADDR_PRIx "\n", TYPE_IMX_EPIT, __func__, offset);
         break;
     }

     DPRINTF("(%s) = 0x%08x\n", imx_epit_reg_name(offset >> 2), reg_value);

     return reg_value;
 }

 /*
  * Must be called from a ptimer_transaction_begin/commit block for
  * s->timer_cmp, but outside of a transaction block of s->timer_reload,
  * so the proper counter value is read.
  */
 static void imx_epit_update_compare_timer(IMXEPITState *s)
 {
     uint64_t counter = 0;
     bool is_oneshot = false;
     /*
      * The compare timer only has to run if the timer peripheral is active
      * and there is an input clock, Otherwise it can be switched off.
      */
     bool is_active = (s->cr & CR_EN) && imx_epit_get_freq(s);
     if (is_active) {
         /*
          * Calculate next timeout for compare timer. Reading the reload
          * counter returns proper results only if pending transactions
          * on it are committed here. Otherwise stale values are be read.
          */
         counter = ptimer_get_count(s->timer_reload);
         uint64_t limit = ptimer_get_limit(s->timer_cmp);
         /*
          * The compare timer is a periodic timer if the limit is at least
          * the compare value. Otherwise it may fire at most once in the
          * current round.
          */
         is_oneshot = (limit < s->cmp);
         if (counter >= s->cmp) {
             /* The compare timer fires in the current round. */
             counter -= s->cmp;
         } else if (!is_oneshot) {
             /*
              * The compare timer fires after a reload, as it is below the
              * compare value already in this round. Note that the counter
              * value calculated below can be above the 32-bit limit, which
              * is legal here because the compare timer is an internal
              * helper ptimer only.
              */
             counter += limit - s->cmp;
         } else {
             /*
              * The compare timer won't fire in this round, and the limit is
              * set to a value below the compare value. This practically means
              * it will never fire, so it can be switched off.
              */
             is_active = false;
         }
     }

     /*
      * Set the compare timer and let it run, or stop it. This is agnostic
      * of CR.OCIEN bit, as this bit affects interrupt generation only. The
      * compare timer needs to run even if no interrupts are to be generated,
      * because the SR.OCIF bit must be updated also.
      * Note that the timer might already be stopped or be running with
      * counter values. However, finding out when an update is needed and
      * when not is not trivial. It's much easier applying the setting again,
      * as this does not harm either and the overhead is negligible.
      */
     if (is_active) {
         ptimer_set_count(s->timer_cmp, counter);
         ptimer_run(s->timer_cmp, is_oneshot ? 1 : 0);
     } else {
         ptimer_stop(s->timer_cmp);
     }

 }

 static void imx_epit_write_cr(IMXEPITState *s, uint32_t value)
 {
     uint32_t oldcr = s->cr;

     s->cr = value & 0x03ffffff;

     if (s->cr & CR_SWR) {
         /*
          * Reset clears CR.SWR again. It does not touch CR.EN, but the timers
          * are still stopped because the input clock is disabled.
          */
         imx_epit_reset(s, false);
     } else {
         uint32_t freq;
         uint32_t toggled_cr_bits = oldcr ^ s->cr;
         /* re-initialize the limits if CR.RLD has changed */
         bool set_limit = toggled_cr_bits & CR_RLD;
         /* set the counter if the timer got just enabled and CR.ENMOD is set */
         bool is_switched_on = (toggled_cr_bits & s->cr) & CR_EN;
         bool set_counter = is_switched_on && (s->cr & CR_ENMOD);

         ptimer_transaction_begin(s->timer_cmp);
         ptimer_transaction_begin(s->timer_reload);
         freq = imx_epit_get_freq(s);
         if (freq) {
             ptimer_set_freq(s->timer_reload, freq);
             ptimer_set_freq(s->timer_cmp, freq);
         }

         if (set_limit || set_counter) {
             uint64_t limit = (s->cr & CR_RLD) ? s->lr : EPIT_TIMER_MAX;
             ptimer_set_limit(s->timer_reload, limit, set_counter ? 1 : 0);
             if (set_limit) {
                 ptimer_set_limit(s->timer_cmp, limit, 0);
             }
         }
         /*
          * If there is an input clock and the peripheral is enabled, then
          * ensure the wall clock timer is ticking. Otherwise stop the timers.
          * The compare timer will be updated later.
          */
         if (freq && (s->cr & CR_EN)) {
             ptimer_run(s->timer_reload, 0);
         } else {
             ptimer_stop(s->timer_reload);
         }
         /* Commit changes to reload timer, so they can propagate. */
         ptimer_transaction_commit(s->timer_reload);
         /* Update compare timer based on the committed reload timer value. */
         imx_epit_update_compare_timer(s);
         ptimer_transaction_commit(s->timer_cmp);
     }

     /*
      * The interrupt state can change due to:
      * - reset clears both SR.OCIF and CR.OCIE
      * - write to CR.EN or CR.OCIE
      */
     imx_epit_update_int(s);
 }

 static void imx_epit_write_sr(IMXEPITState *s, uint32_t value)
 {
     /* writing 1 to SR.OCIF clears this bit and turns the interrupt off */
     if (value & SR_OCIF) {
         s->sr = 0; /* SR.OCIF is the only bit in this register anyway */
         imx_epit_update_int(s);
     }
 }

 static void imx_epit_write_lr(IMXEPITState *s, uint32_t value)
 {
     s->lr = value;

     ptimer_transaction_begin(s->timer_cmp);
     ptimer_transaction_begin(s->timer_reload);
     if (s->cr & CR_RLD) {
         /* Also set the limit if the LRD bit is set */
         /* If IOVW bit is set then set the timer value */
         ptimer_set_limit(s->timer_reload, s->lr, s->cr & CR_IOVW);
         ptimer_set_limit(s->timer_cmp, s->lr, 0);
     } else if (s->cr & CR_IOVW) {
         /* If IOVW bit is set then set the timer value */
         ptimer_set_count(s->timer_reload, s->lr);
     }
     /* Commit the changes to s->timer_reload, so they can propagate. */
     ptimer_transaction_commit(s->timer_reload);
     /* Update the compare timer based on the committed reload timer value. */
     imx_epit_update_compare_timer(s);
     ptimer_transaction_commit(s->timer_cmp);
 }

 static void imx_epit_write_cmp(IMXEPITState *s, uint32_t value)
 {
     s->cmp = value;

     /* Update the compare timer based on the committed reload timer value. */
     ptimer_transaction_begin(s->timer_cmp);
     imx_epit_update_compare_timer(s);
     ptimer_transaction_commit(s->timer_cmp);
 }

 static void imx_epit_write(void *opaque, hwaddr offset, uint64_t value,
                            unsigned size)
 {
     IMXEPITState *s = IMX_EPIT(opaque);

     DPRINTF("(%s, value = 0x%08x)\n", imx_epit_reg_name(offset >> 2),
             (uint32_t)value);

     switch (offset >> 2) {
     case 0: /* CR */
         imx_epit_write_cr(s, (uint32_t)value);
         break;

     case 1: /* SR */
         imx_epit_write_sr(s, (uint32_t)value);
         break;

     case 2: /* LR */
         imx_epit_write_lr(s, (uint32_t)value);
         break;

     case 3: /* CMP */
         imx_epit_write_cmp(s, (uint32_t)value);
         break;

     default:
         qemu_log_mask(LOG_GUEST_ERROR, "[%s]%s: Bad register at offset 0x%"
                       HWADDR_PRIx "\n", TYPE_IMX_EPIT, __func__, offset);
         break;
     }
 }

 static void imx_epit_cmp(void *opaque)
 {
     IMXEPITState *s = IMX_EPIT(opaque);

     /* The cmp ptimer can't be running when the peripheral is disabled */
     assert(s->cr & CR_EN);

     DPRINTF("sr was %d\n", s->sr);
     /* Set interrupt status bit SR.OCIF and update the interrupt state */
     s->sr |= SR_OCIF;
     imx_epit_update_int(s);
 }

 static void imx_epit_reload(void *opaque)
 {
     /* No action required on rollover of timer_reload */
 }

 static const MemoryRegionOps imx_epit_ops = {
     .read = imx_epit_read,
     .write = imx_epit_write,
     .endianness = DEVICE_NATIVE_ENDIAN,
 };

 static const VMStateDescription vmstate_imx_timer_epit = {
     .name = TYPE_IMX_EPIT,
     .version_id = 3,
     .minimum_version_id = 3,
     .fields = (const VMStateField[]) {
         VMSTATE_UINT32(cr, IMXEPITState),
         VMSTATE_UINT32(sr, IMXEPITState),
         VMSTATE_UINT32(lr, IMXEPITState),
         VMSTATE_UINT32(cmp, IMXEPITState),
         VMSTATE_PTIMER(timer_reload, IMXEPITState),
         VMSTATE_PTIMER(timer_cmp, IMXEPITState),
         VMSTATE_END_OF_LIST()
     }
 };

 static void imx_epit_realize(DeviceState *dev, Error **errp)
 {
     IMXEPITState *s = IMX_EPIT(dev);
     SysBusDevice *sbd = SYS_BUS_DEVICE(dev);

     DPRINTF("\n");

     sysbus_init_irq(sbd, &s->irq);
     memory_region_init_io(&s->iomem, OBJECT(s), &imx_epit_ops, s, TYPE_IMX_EPIT,
                           0x00001000);
     sysbus_init_mmio(sbd, &s->iomem);

     /*
      * The reload timer keeps running when the peripheral is enabled. It is a
      * kind of wall clock that does not generate any interrupts. The callback
      * needs to be provided, but it does nothing as the ptimer already supports
      * all necessary reloading functionality.
      */
     s->timer_reload = ptimer_init(imx_epit_reload, s, PTIMER_POLICY_LEGACY);

     /*
      * The compare timer is running only when the peripheral configuration is
      * in a state that will generate compare interrupts.
      */
     s->timer_cmp = ptimer_init(imx_epit_cmp, s, PTIMER_POLICY_LEGACY);
 }

 static void imx_epit_dev_reset(DeviceState *dev)
 {
     IMXEPITState *s = IMX_EPIT(dev);
     imx_epit_reset(s, true);
 }

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

     dc->realize = imx_epit_realize;
     device_class_set_legacy_reset(dc, imx_epit_dev_reset);
     dc->vmsd = &vmstate_imx_timer_epit;
     dc->desc = "i.MX periodic timer";
 }

 static const TypeInfo imx_epit_info = {
     .name = TYPE_IMX_EPIT,
     .parent = TYPE_SYS_BUS_DEVICE,
     .instance_size = sizeof(IMXEPITState),
     .class_init = imx_epit_class_init,
 };

 static void imx_epit_register_types(void)
 {
     type_register_static(&imx_epit_info);
 }

 type_init(imx_epit_register_types)
	/*
	* IMX EPIT Timer
	*
	* Copyright (c) 2008 OK Labs
	* Copyright (c) 2011 NICTA Pty Ltd
	* Originally written by Hans Jiang
	* Updated by Peter Chubb
	* Updated by Jean-Christophe Dubois <jcd@tribudubois.net>
	* Updated by Axel Heider
	*
	* This code is licensed under GPL version 2 or later. See
	* the COPYING file in the top-level directory.
	*
	*/

	#include "qemu/osdep.h"
	#include "hw/timer/imx_epit.h"
	#include "migration/vmstate.h"
	#include "hw/irq.h"
	#include "hw/misc/imx_ccm.h"
	#include "qemu/module.h"
	#include "qemu/log.h"

	#ifndef DEBUG_IMX_EPIT
	#define DEBUG_IMX_EPIT 0
	#endif

	#define DPRINTF(fmt, args...) \
	do { \
	if (DEBUG_IMX_EPIT) { \
	fprintf(stderr, "[%s]%s: " fmt , TYPE_IMX_EPIT, \
	__func__, ##args); \
	} \
	} while (0)

	static const char *imx_epit_reg_name(uint32_t reg)
	{
	switch (reg) {
	case 0:
	return "CR";
	case 1:
	return "SR";
	case 2:
	return "LR";
	case 3:
	return "CMP";
	case 4:
	return "CNT";
	default:
	return "[?]";
	}
	}

	/*
	* Exact clock frequencies vary from board to board.
	* These are typical.
	*/
	static const IMXClk imx_epit_clocks[] = {
	CLK_NONE, /* 00 disabled */
	CLK_IPG, /* 01 ipg_clk, ~532MHz */
	CLK_IPG_HIGH, /* 10 ipg_clk_highfreq */
	CLK_32k, /* 11 ipg_clk_32k -- ~32kHz */
	};

	/*
	* Update interrupt status
	*/
	static void imx_epit_update_int(IMXEPITState *s)
	{
	if ((s->sr & SR_OCIF) && (s->cr & CR_OCIEN) && (s->cr & CR_EN)) {
	qemu_irq_raise(s->irq);
	} else {
	qemu_irq_lower(s->irq);
	}
	}

	static uint32_t imx_epit_get_freq(IMXEPITState *s)
	{
	uint32_t clksrc = extract32(s->cr, CR_CLKSRC_SHIFT, CR_CLKSRC_BITS);
	uint32_t prescaler = 1 + extract32(s->cr, CR_PRESCALE_SHIFT, CR_PRESCALE_BITS);
	uint32_t f_in = imx_ccm_get_clock_frequency(s->ccm, imx_epit_clocks[clksrc]);
	uint32_t freq = f_in / prescaler;
	DPRINTF("ptimer frequency is %u\n", freq);
	return freq;
	}

	/*
	* This is called both on hardware (device) reset and software reset.
	*/
	static void imx_epit_reset(IMXEPITState *s, bool is_hard_reset)
	{
	/* Soft reset doesn't touch some bits; hard reset clears them */
	if (is_hard_reset) {
	s->cr = 0;
	} else {
	s->cr &= (CR_EN\|CR_ENMOD\|CR_STOPEN\|CR_DOZEN\|CR_WAITEN\|CR_DBGEN);
	}
	s->sr = 0;
	s->lr = EPIT_TIMER_MAX;
	s->cmp = 0;
	ptimer_transaction_begin(s->timer_cmp);
	ptimer_transaction_begin(s->timer_reload);

	/*
	* The reset switches off the input clock, so even if the CR.EN is still
	* set, the timers are no longer running.
	*/
	assert(imx_epit_get_freq(s) == 0);
	ptimer_stop(s->timer_cmp);
	ptimer_stop(s->timer_reload);
	/* init both timers to EPIT_TIMER_MAX */
	ptimer_set_limit(s->timer_cmp, EPIT_TIMER_MAX, 1);
	ptimer_set_limit(s->timer_reload, EPIT_TIMER_MAX, 1);
	ptimer_transaction_commit(s->timer_cmp);
	ptimer_transaction_commit(s->timer_reload);
	}

	static uint64_t imx_epit_read(void *opaque, hwaddr offset, unsigned size)
	{
	IMXEPITState *s = IMX_EPIT(opaque);
	uint32_t reg_value = 0;

	switch (offset >> 2) {
	case 0: /* Control Register */
	reg_value = s->cr;
	break;

	case 1: /* Status Register */
	reg_value = s->sr;
	break;

	case 2: /* LR - ticks*/
	reg_value = s->lr;
	break;

	case 3: /* CMP */
	reg_value = s->cmp;
	break;

	case 4: /* CNT */
	reg_value = ptimer_get_count(s->timer_reload);
	break;

	default:
	qemu_log_mask(LOG_GUEST_ERROR, "[%s]%s: Bad register at offset 0x%"
	HWADDR_PRIx "\n", TYPE_IMX_EPIT, __func__, offset);
	break;
	}

	DPRINTF("(%s) = 0x%08x\n", imx_epit_reg_name(offset >> 2), reg_value);

	return reg_value;
	}

	/*
	* Must be called from a ptimer_transaction_begin/commit block for
	* s->timer_cmp, but outside of a transaction block of s->timer_reload,
	* so the proper counter value is read.
	*/
	static void imx_epit_update_compare_timer(IMXEPITState *s)
	{
	uint64_t counter = 0;
	bool is_oneshot = false;
	/*
	* The compare timer only has to run if the timer peripheral is active
	* and there is an input clock, Otherwise it can be switched off.
	*/
	bool is_active = (s->cr & CR_EN) && imx_epit_get_freq(s);
	if (is_active) {
	/*
	* Calculate next timeout for compare timer. Reading the reload
	* counter returns proper results only if pending transactions
	* on it are committed here. Otherwise stale values are be read.
	*/
	counter = ptimer_get_count(s->timer_reload);
	uint64_t limit = ptimer_get_limit(s->timer_cmp);
	/*
	* The compare timer is a periodic timer if the limit is at least
	* the compare value. Otherwise it may fire at most once in the
	* current round.
	*/
	is_oneshot = (limit < s->cmp);
	if (counter >= s->cmp) {
	/* The compare timer fires in the current round. */
	counter -= s->cmp;
	} else if (!is_oneshot) {
	/*
	* The compare timer fires after a reload, as it is below the
	* compare value already in this round. Note that the counter
	* value calculated below can be above the 32-bit limit, which
	* is legal here because the compare timer is an internal
	* helper ptimer only.
	*/
	counter += limit - s->cmp;
	} else {
	/*
	* The compare timer won't fire in this round, and the limit is
	* set to a value below the compare value. This practically means
	* it will never fire, so it can be switched off.
	*/
	is_active = false;
	}
	}

	/*
	* Set the compare timer and let it run, or stop it. This is agnostic
	* of CR.OCIEN bit, as this bit affects interrupt generation only. The
	* compare timer needs to run even if no interrupts are to be generated,
	* because the SR.OCIF bit must be updated also.
	* Note that the timer might already be stopped or be running with
	* counter values. However, finding out when an update is needed and
	* when not is not trivial. It's much easier applying the setting again,
	* as this does not harm either and the overhead is negligible.
	*/
	if (is_active) {
	ptimer_set_count(s->timer_cmp, counter);
	ptimer_run(s->timer_cmp, is_oneshot ? 1 : 0);
	} else {
	ptimer_stop(s->timer_cmp);
	}

	}

	static void imx_epit_write_cr(IMXEPITState *s, uint32_t value)
	{
	uint32_t oldcr = s->cr;

	s->cr = value & 0x03ffffff;

	if (s->cr & CR_SWR) {
	/*
	* Reset clears CR.SWR again. It does not touch CR.EN, but the timers
	* are still stopped because the input clock is disabled.
	*/
	imx_epit_reset(s, false);
	} else {
	uint32_t freq;
	uint32_t toggled_cr_bits = oldcr ^ s->cr;
	/* re-initialize the limits if CR.RLD has changed */
	bool set_limit = toggled_cr_bits & CR_RLD;
	/* set the counter if the timer got just enabled and CR.ENMOD is set */
	bool is_switched_on = (toggled_cr_bits & s->cr) & CR_EN;
	bool set_counter = is_switched_on && (s->cr & CR_ENMOD);

	ptimer_transaction_begin(s->timer_cmp);
	ptimer_transaction_begin(s->timer_reload);
	freq = imx_epit_get_freq(s);
	if (freq) {
	ptimer_set_freq(s->timer_reload, freq);
	ptimer_set_freq(s->timer_cmp, freq);
	}

	if (set_limit \|\| set_counter) {
	uint64_t limit = (s->cr & CR_RLD) ? s->lr : EPIT_TIMER_MAX;
	ptimer_set_limit(s->timer_reload, limit, set_counter ? 1 : 0);
	if (set_limit) {
	ptimer_set_limit(s->timer_cmp, limit, 0);
	}
	}
	/*
	* If there is an input clock and the peripheral is enabled, then
	* ensure the wall clock timer is ticking. Otherwise stop the timers.
	* The compare timer will be updated later.
	*/
	if (freq && (s->cr & CR_EN)) {
	ptimer_run(s->timer_reload, 0);
	} else {
	ptimer_stop(s->timer_reload);
	}
	/* Commit changes to reload timer, so they can propagate. */
	ptimer_transaction_commit(s->timer_reload);
	/* Update compare timer based on the committed reload timer value. */
	imx_epit_update_compare_timer(s);
	ptimer_transaction_commit(s->timer_cmp);
	}

	/*
	* The interrupt state can change due to:
	* - reset clears both SR.OCIF and CR.OCIE
	* - write to CR.EN or CR.OCIE
	*/
	imx_epit_update_int(s);
	}

	static void imx_epit_write_sr(IMXEPITState *s, uint32_t value)
	{
	/* writing 1 to SR.OCIF clears this bit and turns the interrupt off */
	if (value & SR_OCIF) {
	s->sr = 0; /* SR.OCIF is the only bit in this register anyway */
	imx_epit_update_int(s);
	}
	}

	static void imx_epit_write_lr(IMXEPITState *s, uint32_t value)
	{
	s->lr = value;

	ptimer_transaction_begin(s->timer_cmp);
	ptimer_transaction_begin(s->timer_reload);
	if (s->cr & CR_RLD) {
	/* Also set the limit if the LRD bit is set */
	/* If IOVW bit is set then set the timer value */
	ptimer_set_limit(s->timer_reload, s->lr, s->cr & CR_IOVW);
	ptimer_set_limit(s->timer_cmp, s->lr, 0);
	} else if (s->cr & CR_IOVW) {
	/* If IOVW bit is set then set the timer value */
	ptimer_set_count(s->timer_reload, s->lr);
	}
	/* Commit the changes to s->timer_reload, so they can propagate. */
	ptimer_transaction_commit(s->timer_reload);
	/* Update the compare timer based on the committed reload timer value. */
	imx_epit_update_compare_timer(s);
	ptimer_transaction_commit(s->timer_cmp);
	}

	static void imx_epit_write_cmp(IMXEPITState *s, uint32_t value)
	{
	s->cmp = value;

	/* Update the compare timer based on the committed reload timer value. */
	ptimer_transaction_begin(s->timer_cmp);
	imx_epit_update_compare_timer(s);
	ptimer_transaction_commit(s->timer_cmp);
	}

	static void imx_epit_write(void *opaque, hwaddr offset, uint64_t value,
	unsigned size)
	{
	IMXEPITState *s = IMX_EPIT(opaque);

	DPRINTF("(%s, value = 0x%08x)\n", imx_epit_reg_name(offset >> 2),
	(uint32_t)value);

	switch (offset >> 2) {
	case 0: /* CR */
	imx_epit_write_cr(s, (uint32_t)value);
	break;

	case 1: /* SR */
	imx_epit_write_sr(s, (uint32_t)value);
	break;

	case 2: /* LR */
	imx_epit_write_lr(s, (uint32_t)value);
	break;

	case 3: /* CMP */
	imx_epit_write_cmp(s, (uint32_t)value);
	break;

	default:
	qemu_log_mask(LOG_GUEST_ERROR, "[%s]%s: Bad register at offset 0x%"
	HWADDR_PRIx "\n", TYPE_IMX_EPIT, __func__, offset);
	break;
	}
	}

	static void imx_epit_cmp(void *opaque)
	{
	IMXEPITState *s = IMX_EPIT(opaque);

	/* The cmp ptimer can't be running when the peripheral is disabled */
	assert(s->cr & CR_EN);

	DPRINTF("sr was %d\n", s->sr);
	/* Set interrupt status bit SR.OCIF and update the interrupt state */
	s->sr \|= SR_OCIF;
	imx_epit_update_int(s);
	}

	static void imx_epit_reload(void *opaque)
	{
	/* No action required on rollover of timer_reload */
	}

	static const MemoryRegionOps imx_epit_ops = {
	.read = imx_epit_read,
	.write = imx_epit_write,
	.endianness = DEVICE_NATIVE_ENDIAN,
	};

	static const VMStateDescription vmstate_imx_timer_epit = {
	.name = TYPE_IMX_EPIT,
	.version_id = 3,
	.minimum_version_id = 3,
	.fields = (const VMStateField[]) {
	VMSTATE_UINT32(cr, IMXEPITState),
	VMSTATE_UINT32(sr, IMXEPITState),
	VMSTATE_UINT32(lr, IMXEPITState),
	VMSTATE_UINT32(cmp, IMXEPITState),
	VMSTATE_PTIMER(timer_reload, IMXEPITState),
	VMSTATE_PTIMER(timer_cmp, IMXEPITState),
	VMSTATE_END_OF_LIST()
	}
	};

	static void imx_epit_realize(DeviceState dev, Error *errp)
	{
	IMXEPITState *s = IMX_EPIT(dev);
	SysBusDevice *sbd = SYS_BUS_DEVICE(dev);

	DPRINTF("\n");

	sysbus_init_irq(sbd, &s->irq);
	memory_region_init_io(&s->iomem, OBJECT(s), &imx_epit_ops, s, TYPE_IMX_EPIT,
	0x00001000);
	sysbus_init_mmio(sbd, &s->iomem);

	/*
	* The reload timer keeps running when the peripheral is enabled. It is a
	* kind of wall clock that does not generate any interrupts. The callback
	* needs to be provided, but it does nothing as the ptimer already supports
	* all necessary reloading functionality.
	*/
	s->timer_reload = ptimer_init(imx_epit_reload, s, PTIMER_POLICY_LEGACY);

	/*
	* The compare timer is running only when the peripheral configuration is
	* in a state that will generate compare interrupts.
	*/
	s->timer_cmp = ptimer_init(imx_epit_cmp, s, PTIMER_POLICY_LEGACY);
	}

	static void imx_epit_dev_reset(DeviceState *dev)
	{
	IMXEPITState *s = IMX_EPIT(dev);
	imx_epit_reset(s, true);
	}

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

	dc->realize = imx_epit_realize;
	device_class_set_legacy_reset(dc, imx_epit_dev_reset);
	dc->vmsd = &vmstate_imx_timer_epit;
	dc->desc = "i.MX periodic timer";
	}

	static const TypeInfo imx_epit_info = {
	.name = TYPE_IMX_EPIT,
	.parent = TYPE_SYS_BUS_DEVICE,
	.instance_size = sizeof(IMXEPITState),
	.class_init = imx_epit_class_init,
	};

	static void imx_epit_register_types(void)
	{
	type_register_static(&imx_epit_info);
	}

	type_init(imx_epit_register_types)