hw/timer/armv7m_systick.c - qemu - Git at Google

 /*
  * ARMv7M SysTick timer
  *
  * Copyright (c) 2006-2007 CodeSourcery.
  * Written by Paul Brook
  * Copyright (c) 2017 Linaro Ltd
  * Written by Peter Maydell
  *
  * This code is licensed under the GPL (version 2 or later).
  */

 #include "qemu/osdep.h"
 #include "hw/timer/armv7m_systick.h"
 #include "migration/vmstate.h"
 #include "hw/irq.h"
 #include "hw/sysbus.h"
 #include "hw/qdev-clock.h"
 #include "qemu/timer.h"
 #include "qemu/log.h"
 #include "qemu/module.h"
 #include "qapi/error.h"
 #include "trace.h"

 #define SYSTICK_ENABLE    (1 << 0)
 #define SYSTICK_TICKINT   (1 << 1)
 #define SYSTICK_CLKSOURCE (1 << 2)
 #define SYSTICK_COUNTFLAG (1 << 16)

 #define SYSCALIB_NOREF (1U << 31)
 #define SYSCALIB_SKEW (1U << 30)
 #define SYSCALIB_TENMS ((1U << 24) - 1)

 static void systick_set_period_from_clock(SysTickState *s)
 {
     /*
      * Set the ptimer period from whichever clock is selected.
      * Must be called from within a ptimer transaction block.
      */
     if (s->control & SYSTICK_CLKSOURCE) {
         ptimer_set_period_from_clock(s->ptimer, s->cpuclk, 1);
     } else {
         ptimer_set_period_from_clock(s->ptimer, s->refclk, 1);
     }
 }

 static void systick_timer_tick(void *opaque)
 {
     SysTickState *s = (SysTickState *)opaque;

     trace_systick_timer_tick();

     s->control |= SYSTICK_COUNTFLAG;
     if (s->control & SYSTICK_TICKINT) {
         /* Tell the NVIC to pend the SysTick exception */
         qemu_irq_pulse(s->irq);
     }
     if (ptimer_get_limit(s->ptimer) == 0) {
         /*
          * Timer expiry with SYST_RVR zero disables the timer
          * (but doesn't clear SYST_CSR.ENABLE)
          */
         ptimer_stop(s->ptimer);
     }
 }

 static MemTxResult systick_read(void *opaque, hwaddr addr, uint64_t *data,
                                 unsigned size, MemTxAttrs attrs)
 {
     SysTickState *s = opaque;
     uint32_t val;

     if (attrs.user) {
         /* Generate BusFault for unprivileged accesses */
         return MEMTX_ERROR;
     }

     switch (addr) {
     case 0x0: /* SysTick Control and Status.  */
         val = s->control;
         s->control &= ~SYSTICK_COUNTFLAG;
         break;
     case 0x4: /* SysTick Reload Value.  */
         val = ptimer_get_limit(s->ptimer);
         break;
     case 0x8: /* SysTick Current Value.  */
         val = ptimer_get_count(s->ptimer);
         break;
     case 0xc: /* SysTick Calibration Value.  */
         /*
          * In real hardware it is possible to make this register report
          * a different value from what the reference clock is actually
          * running at. We don't model that (which usually happens due
          * to integration errors in the real hardware) and instead always
          * report the theoretical correct value as described in the
          * knowledgebase article at
          * https://developer.arm.com/documentation/ka001325/latest
          * If necessary, we could implement an extra QOM property on this
          * device to force the STCALIB value to something different from
          * the "correct" value.
          */
         if (!clock_has_source(s->refclk)) {
             val = SYSCALIB_NOREF;
             break;
         }
         val = clock_ns_to_ticks(s->refclk, 10 * SCALE_MS) - 1;
         val &= SYSCALIB_TENMS;
         if (clock_ticks_to_ns(s->refclk, val + 1) != 10 * SCALE_MS) {
             /* report that tick count does not yield exactly 10ms */
             val |= SYSCALIB_SKEW;
         }
         break;
     default:
         val = 0;
         qemu_log_mask(LOG_GUEST_ERROR,
                       "SysTick: Bad read offset 0x%" HWADDR_PRIx "\n", addr);
         break;
     }

     trace_systick_read(addr, val, size);
     *data = val;
     return MEMTX_OK;
 }

 static MemTxResult systick_write(void *opaque, hwaddr addr,
                                  uint64_t value, unsigned size,
                                  MemTxAttrs attrs)
 {
     SysTickState *s = opaque;

     if (attrs.user) {
         /* Generate BusFault for unprivileged accesses */
         return MEMTX_ERROR;
     }

     trace_systick_write(addr, value, size);

     switch (addr) {
     case 0x0: /* SysTick Control and Status.  */
     {
         uint32_t oldval;

         if (!clock_has_source(s->refclk)) {
             /* This bit is always 1 if there is no external refclk */
             value |= SYSTICK_CLKSOURCE;
         }

         ptimer_transaction_begin(s->ptimer);
         oldval = s->control;
         s->control &= 0xfffffff8;
         s->control |= value & 7;

         if ((oldval ^ value) & SYSTICK_CLKSOURCE) {
             systick_set_period_from_clock(s);
         }

         if ((oldval ^ value) & SYSTICK_ENABLE) {
             if (value & SYSTICK_ENABLE) {
                 ptimer_run(s->ptimer, 0);
             } else {
                 ptimer_stop(s->ptimer);
             }
         }
         ptimer_transaction_commit(s->ptimer);
         break;
     }
     case 0x4: /* SysTick Reload Value.  */
         ptimer_transaction_begin(s->ptimer);
         ptimer_set_limit(s->ptimer, value & 0xffffff, 0);
         ptimer_transaction_commit(s->ptimer);
         break;
     case 0x8: /* SysTick Current Value. */
         /*
          * Writing any value clears SYST_CVR to zero and clears
          * SYST_CSR.COUNTFLAG. The counter will then reload from SYST_RVR
          * on the next clock edge unless SYST_RVR is zero.
          */
         ptimer_transaction_begin(s->ptimer);
         if (ptimer_get_limit(s->ptimer) == 0) {
             ptimer_stop(s->ptimer);
         }
         ptimer_set_count(s->ptimer, 0);
         s->control &= ~SYSTICK_COUNTFLAG;
         ptimer_transaction_commit(s->ptimer);
         break;
     default:
         qemu_log_mask(LOG_GUEST_ERROR,
                       "SysTick: Bad write offset 0x%" HWADDR_PRIx "\n", addr);
     }
     return MEMTX_OK;
 }

 static const MemoryRegionOps systick_ops = {
     .read_with_attrs = systick_read,
     .write_with_attrs = systick_write,
     .endianness = DEVICE_NATIVE_ENDIAN,
     .valid.min_access_size = 4,
     .valid.max_access_size = 4,
 };

 static void systick_reset(DeviceState *dev)
 {
     SysTickState *s = SYSTICK(dev);

     ptimer_transaction_begin(s->ptimer);
     s->control = 0;
     if (!clock_has_source(s->refclk)) {
         /* This bit is always 1 if there is no external refclk */
         s->control |= SYSTICK_CLKSOURCE;
     }
     ptimer_stop(s->ptimer);
     ptimer_set_count(s->ptimer, 0);
     ptimer_set_limit(s->ptimer, 0, 0);
     systick_set_period_from_clock(s);
     ptimer_transaction_commit(s->ptimer);
 }

 static void systick_cpuclk_update(void *opaque, ClockEvent event)
 {
     SysTickState *s = SYSTICK(opaque);

     if (!(s->control & SYSTICK_CLKSOURCE)) {
         /* currently using refclk, we can ignore cpuclk changes */
     }

     ptimer_transaction_begin(s->ptimer);
     ptimer_set_period_from_clock(s->ptimer, s->cpuclk, 1);
     ptimer_transaction_commit(s->ptimer);
 }

 static void systick_refclk_update(void *opaque, ClockEvent event)
 {
     SysTickState *s = SYSTICK(opaque);

     if (s->control & SYSTICK_CLKSOURCE) {
         /* currently using cpuclk, we can ignore refclk changes */
     }

     ptimer_transaction_begin(s->ptimer);
     ptimer_set_period_from_clock(s->ptimer, s->refclk, 1);
     ptimer_transaction_commit(s->ptimer);
 }

 static void systick_instance_init(Object *obj)
 {
     SysBusDevice *sbd = SYS_BUS_DEVICE(obj);
     SysTickState *s = SYSTICK(obj);

     memory_region_init_io(&s->iomem, obj, &systick_ops, s, "systick", 0xe0);
     sysbus_init_mmio(sbd, &s->iomem);
     sysbus_init_irq(sbd, &s->irq);

     s->refclk = qdev_init_clock_in(DEVICE(obj), "refclk",
                                    systick_refclk_update, s, ClockUpdate);
     s->cpuclk = qdev_init_clock_in(DEVICE(obj), "cpuclk",
                                    systick_cpuclk_update, s, ClockUpdate);
 }

 static void systick_realize(DeviceState *dev, Error **errp)
 {
     SysTickState *s = SYSTICK(dev);
     s->ptimer = ptimer_init(systick_timer_tick, s,
                             PTIMER_POLICY_WRAP_AFTER_ONE_PERIOD |
                             PTIMER_POLICY_NO_COUNTER_ROUND_DOWN |
                             PTIMER_POLICY_NO_IMMEDIATE_RELOAD |
                             PTIMER_POLICY_TRIGGER_ONLY_ON_DECREMENT);

     if (!clock_has_source(s->cpuclk)) {
         error_setg(errp, "systick: cpuclk must be connected");
         return;
     }
     /* It's OK not to connect the refclk */
 }

 static const VMStateDescription vmstate_systick = {
     .name = "armv7m_systick",
     .version_id = 3,
     .minimum_version_id = 3,
     .fields = (VMStateField[]) {
         VMSTATE_CLOCK(refclk, SysTickState),
         VMSTATE_CLOCK(cpuclk, SysTickState),
         VMSTATE_UINT32(control, SysTickState),
         VMSTATE_INT64(tick, SysTickState),
         VMSTATE_PTIMER(ptimer, SysTickState),
         VMSTATE_END_OF_LIST()
     }
 };

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

     dc->vmsd = &vmstate_systick;
     dc->reset = systick_reset;
     dc->realize = systick_realize;
 }

 static const TypeInfo armv7m_systick_info = {
     .name = TYPE_SYSTICK,
     .parent = TYPE_SYS_BUS_DEVICE,
     .instance_init = systick_instance_init,
     .instance_size = sizeof(SysTickState),
     .class_init = systick_class_init,
 };

 static void armv7m_systick_register_types(void)
 {
     type_register_static(&armv7m_systick_info);
 }

 type_init(armv7m_systick_register_types)
	/*
	* ARMv7M SysTick timer
	*
	* Copyright (c) 2006-2007 CodeSourcery.
	* Written by Paul Brook
	* Copyright (c) 2017 Linaro Ltd
	* Written by Peter Maydell
	*
	* This code is licensed under the GPL (version 2 or later).
	*/

	#include "qemu/osdep.h"
	#include "hw/timer/armv7m_systick.h"
	#include "migration/vmstate.h"
	#include "hw/irq.h"
	#include "hw/sysbus.h"
	#include "hw/qdev-clock.h"
	#include "qemu/timer.h"
	#include "qemu/log.h"
	#include "qemu/module.h"
	#include "qapi/error.h"
	#include "trace.h"

	#define SYSTICK_ENABLE (1 << 0)
	#define SYSTICK_TICKINT (1 << 1)
	#define SYSTICK_CLKSOURCE (1 << 2)
	#define SYSTICK_COUNTFLAG (1 << 16)

	#define SYSCALIB_NOREF (1U << 31)
	#define SYSCALIB_SKEW (1U << 30)
	#define SYSCALIB_TENMS ((1U << 24) - 1)

	static void systick_set_period_from_clock(SysTickState *s)
	{
	/*
	* Set the ptimer period from whichever clock is selected.
	* Must be called from within a ptimer transaction block.
	*/
	if (s->control & SYSTICK_CLKSOURCE) {
	ptimer_set_period_from_clock(s->ptimer, s->cpuclk, 1);
	} else {
	ptimer_set_period_from_clock(s->ptimer, s->refclk, 1);
	}
	}

	static void systick_timer_tick(void *opaque)
	{
	SysTickState s = (SysTickState )opaque;

	trace_systick_timer_tick();

	s->control \|= SYSTICK_COUNTFLAG;
	if (s->control & SYSTICK_TICKINT) {
	/* Tell the NVIC to pend the SysTick exception */
	qemu_irq_pulse(s->irq);
	}
	if (ptimer_get_limit(s->ptimer) == 0) {
	/*
	* Timer expiry with SYST_RVR zero disables the timer
	* (but doesn't clear SYST_CSR.ENABLE)
	*/
	ptimer_stop(s->ptimer);
	}
	}

	static MemTxResult systick_read(void opaque, hwaddr addr, uint64_t data,
	unsigned size, MemTxAttrs attrs)
	{
	SysTickState *s = opaque;
	uint32_t val;

	if (attrs.user) {
	/* Generate BusFault for unprivileged accesses */
	return MEMTX_ERROR;
	}

	switch (addr) {
	case 0x0: /* SysTick Control and Status. */
	val = s->control;
	s->control &= ~SYSTICK_COUNTFLAG;
	break;
	case 0x4: /* SysTick Reload Value. */
	val = ptimer_get_limit(s->ptimer);
	break;
	case 0x8: /* SysTick Current Value. */
	val = ptimer_get_count(s->ptimer);
	break;
	case 0xc: /* SysTick Calibration Value. */
	/*
	* In real hardware it is possible to make this register report
	* a different value from what the reference clock is actually
	* running at. We don't model that (which usually happens due
	* to integration errors in the real hardware) and instead always
	* report the theoretical correct value as described in the
	* knowledgebase article at
	* https://developer.arm.com/documentation/ka001325/latest
	* If necessary, we could implement an extra QOM property on this
	* device to force the STCALIB value to something different from
	* the "correct" value.
	*/
	if (!clock_has_source(s->refclk)) {
	val = SYSCALIB_NOREF;
	break;
	}
	val = clock_ns_to_ticks(s->refclk, 10 * SCALE_MS) - 1;
	val &= SYSCALIB_TENMS;
	if (clock_ticks_to_ns(s->refclk, val + 1) != 10 * SCALE_MS) {
	/* report that tick count does not yield exactly 10ms */
	val \|= SYSCALIB_SKEW;
	}
	break;
	default:
	val = 0;
	qemu_log_mask(LOG_GUEST_ERROR,
	"SysTick: Bad read offset 0x%" HWADDR_PRIx "\n", addr);
	break;
	}

	trace_systick_read(addr, val, size);
	*data = val;
	return MEMTX_OK;
	}

	static MemTxResult systick_write(void *opaque, hwaddr addr,
	uint64_t value, unsigned size,
	MemTxAttrs attrs)
	{
	SysTickState *s = opaque;

	if (attrs.user) {
	/* Generate BusFault for unprivileged accesses */
	return MEMTX_ERROR;
	}

	trace_systick_write(addr, value, size);

	switch (addr) {
	case 0x0: /* SysTick Control and Status. */
	{
	uint32_t oldval;

	if (!clock_has_source(s->refclk)) {
	/* This bit is always 1 if there is no external refclk */
	value \|= SYSTICK_CLKSOURCE;
	}

	ptimer_transaction_begin(s->ptimer);
	oldval = s->control;
	s->control &= 0xfffffff8;
	s->control \|= value & 7;

	if ((oldval ^ value) & SYSTICK_CLKSOURCE) {
	systick_set_period_from_clock(s);
	}

	if ((oldval ^ value) & SYSTICK_ENABLE) {
	if (value & SYSTICK_ENABLE) {
	ptimer_run(s->ptimer, 0);
	} else {
	ptimer_stop(s->ptimer);
	}
	}
	ptimer_transaction_commit(s->ptimer);
	break;
	}
	case 0x4: /* SysTick Reload Value. */
	ptimer_transaction_begin(s->ptimer);
	ptimer_set_limit(s->ptimer, value & 0xffffff, 0);
	ptimer_transaction_commit(s->ptimer);
	break;
	case 0x8: /* SysTick Current Value. */
	/*
	* Writing any value clears SYST_CVR to zero and clears
	* SYST_CSR.COUNTFLAG. The counter will then reload from SYST_RVR
	* on the next clock edge unless SYST_RVR is zero.
	*/
	ptimer_transaction_begin(s->ptimer);
	if (ptimer_get_limit(s->ptimer) == 0) {
	ptimer_stop(s->ptimer);
	}
	ptimer_set_count(s->ptimer, 0);
	s->control &= ~SYSTICK_COUNTFLAG;
	ptimer_transaction_commit(s->ptimer);
	break;
	default:
	qemu_log_mask(LOG_GUEST_ERROR,
	"SysTick: Bad write offset 0x%" HWADDR_PRIx "\n", addr);
	}
	return MEMTX_OK;
	}

	static const MemoryRegionOps systick_ops = {
	.read_with_attrs = systick_read,
	.write_with_attrs = systick_write,
	.endianness = DEVICE_NATIVE_ENDIAN,
	.valid.min_access_size = 4,
	.valid.max_access_size = 4,
	};

	static void systick_reset(DeviceState *dev)
	{
	SysTickState *s = SYSTICK(dev);

	ptimer_transaction_begin(s->ptimer);
	s->control = 0;
	if (!clock_has_source(s->refclk)) {
	/* This bit is always 1 if there is no external refclk */
	s->control \|= SYSTICK_CLKSOURCE;
	}
	ptimer_stop(s->ptimer);
	ptimer_set_count(s->ptimer, 0);
	ptimer_set_limit(s->ptimer, 0, 0);
	systick_set_period_from_clock(s);
	ptimer_transaction_commit(s->ptimer);
	}

	static void systick_cpuclk_update(void *opaque, ClockEvent event)
	{
	SysTickState *s = SYSTICK(opaque);

	if (!(s->control & SYSTICK_CLKSOURCE)) {
	/* currently using refclk, we can ignore cpuclk changes */
	}

	ptimer_transaction_begin(s->ptimer);
	ptimer_set_period_from_clock(s->ptimer, s->cpuclk, 1);
	ptimer_transaction_commit(s->ptimer);
	}

	static void systick_refclk_update(void *opaque, ClockEvent event)
	{
	SysTickState *s = SYSTICK(opaque);

	if (s->control & SYSTICK_CLKSOURCE) {
	/* currently using cpuclk, we can ignore refclk changes */
	}

	ptimer_transaction_begin(s->ptimer);
	ptimer_set_period_from_clock(s->ptimer, s->refclk, 1);
	ptimer_transaction_commit(s->ptimer);
	}

	static void systick_instance_init(Object *obj)
	{
	SysBusDevice *sbd = SYS_BUS_DEVICE(obj);
	SysTickState *s = SYSTICK(obj);

	memory_region_init_io(&s->iomem, obj, &systick_ops, s, "systick", 0xe0);
	sysbus_init_mmio(sbd, &s->iomem);
	sysbus_init_irq(sbd, &s->irq);

	s->refclk = qdev_init_clock_in(DEVICE(obj), "refclk",
	systick_refclk_update, s, ClockUpdate);
	s->cpuclk = qdev_init_clock_in(DEVICE(obj), "cpuclk",
	systick_cpuclk_update, s, ClockUpdate);
	}

	static void systick_realize(DeviceState dev, Error *errp)
	{
	SysTickState *s = SYSTICK(dev);
	s->ptimer = ptimer_init(systick_timer_tick, s,
	PTIMER_POLICY_WRAP_AFTER_ONE_PERIOD \|
	PTIMER_POLICY_NO_COUNTER_ROUND_DOWN \|
	PTIMER_POLICY_NO_IMMEDIATE_RELOAD \|
	PTIMER_POLICY_TRIGGER_ONLY_ON_DECREMENT);

	if (!clock_has_source(s->cpuclk)) {
	error_setg(errp, "systick: cpuclk must be connected");
	return;
	}
	/* It's OK not to connect the refclk */
	}

	static const VMStateDescription vmstate_systick = {
	.name = "armv7m_systick",
	.version_id = 3,
	.minimum_version_id = 3,
	.fields = (VMStateField[]) {
	VMSTATE_CLOCK(refclk, SysTickState),
	VMSTATE_CLOCK(cpuclk, SysTickState),
	VMSTATE_UINT32(control, SysTickState),
	VMSTATE_INT64(tick, SysTickState),
	VMSTATE_PTIMER(ptimer, SysTickState),
	VMSTATE_END_OF_LIST()
	}
	};

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

	dc->vmsd = &vmstate_systick;
	dc->reset = systick_reset;
	dc->realize = systick_realize;
	}

	static const TypeInfo armv7m_systick_info = {
	.name = TYPE_SYSTICK,
	.parent = TYPE_SYS_BUS_DEVICE,
	.instance_init = systick_instance_init,
	.instance_size = sizeof(SysTickState),
	.class_init = systick_class_init,
	};

	static void armv7m_systick_register_types(void)
	{
	type_register_static(&armv7m_systick_info);
	}

	type_init(armv7m_systick_register_types)