/*
* 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)
