/*
* 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 "qemu-common.h"
#include "hw/sysbus.h"
#include "qemu/timer.h"
#include "qemu/log.h"
#include "trace.h"
/* qemu timers run at 1GHz. We want something closer to 1MHz. */
#define SYSTICK_SCALE 1000ULL
#define SYSTICK_ENABLE (1 << 0)
#define SYSTICK_TICKINT (1 << 1)
#define SYSTICK_CLKSOURCE (1 << 2)
#define SYSTICK_COUNTFLAG (1 << 16)
int system_clock_scale;
/* Conversion factor from qemu timer to SysTick frequencies. */
static inline int64_t systick_scale(SysTickState *s)
{
if (s->control & SYSTICK_CLKSOURCE) {
return system_clock_scale;
} else {
return 1000;
}
}
static void systick_reload(SysTickState *s, int reset)
{
/* The Cortex-M3 Devices Generic User Guide says that "When the
* ENABLE bit is set to 1, the counter loads the RELOAD value from the
* SYST RVR register and then counts down". So, we need to check the
* ENABLE bit before reloading the value.
*/
trace_systick_reload();
if ((s->control & SYSTICK_ENABLE) == 0) {
return;
}
if (reset) {
s->tick = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL);
}
s->tick += (s->reload + 1) * systick_scale(s);
timer_mod(s->timer, s->tick);
}
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 (s->reload == 0) {
s->control &= ~SYSTICK_ENABLE;
} else {
systick_reload(s, 0);
}
}
static uint64_t systick_read(void *opaque, hwaddr addr, unsigned size)
{
SysTickState *s = opaque;
uint32_t val;
switch (addr) {
case 0x0: /* SysTick Control and Status. */
val = s->control;
s->control &= ~SYSTICK_COUNTFLAG;
break;
case 0x4: /* SysTick Reload Value. */
val = s->reload;
break;
case 0x8: /* SysTick Current Value. */
{
int64_t t;
if ((s->control & SYSTICK_ENABLE) == 0) {
val = 0;
break;
}
t = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL);
if (t >= s->tick) {
val = 0;
break;
}
val = ((s->tick - (t + 1)) / systick_scale(s)) + 1;
/* The interrupt in triggered when the timer reaches zero.
However the counter is not reloaded until the next clock
tick. This is a hack to return zero during the first tick. */
if (val > s->reload) {
val = 0;
}
break;
}
case 0xc: /* SysTick Calibration Value. */
val = 10000;
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);
return val;
}
static void systick_write(void *opaque, hwaddr addr,
uint64_t value, unsigned size)
{
SysTickState *s = opaque;
trace_systick_write(addr, value, size);
switch (addr) {
case 0x0: /* SysTick Control and Status. */
{
uint32_t oldval = s->control;
s->control &= 0xfffffff8;
s->control |= value & 7;
if ((oldval ^ value) & SYSTICK_ENABLE) {
int64_t now = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL);
if (value & SYSTICK_ENABLE) {
if (s->tick) {
s->tick += now;
timer_mod(s->timer, s->tick);
} else {
systick_reload(s, 1);
}
} else {
timer_del(s->timer);
s->tick -= now;
if (s->tick < 0) {
s->tick = 0;
}
}
} else if ((oldval ^ value) & SYSTICK_CLKSOURCE) {
/* This is a hack. Force the timer to be reloaded
when the reference clock is changed. */
systick_reload(s, 1);
}
break;
}
case 0x4: /* SysTick Reload Value. */
s->reload = value;
break;
case 0x8: /* SysTick Current Value. Writes reload the timer. */
systick_reload(s, 1);
s->control &= ~SYSTICK_COUNTFLAG;
break;
default:
qemu_log_mask(LOG_GUEST_ERROR,
"SysTick: Bad write offset 0x%" HWADDR_PRIx "\n", addr);
}
}
static const MemoryRegionOps systick_ops = {
.read = systick_read,
.write = 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);
s->control = 0;
s->reload = 0;
s->tick = 0;
timer_del(s->timer);
}
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->timer = timer_new_ns(QEMU_CLOCK_VIRTUAL, systick_timer_tick, s);
}
static const VMStateDescription vmstate_systick = {
.name = "armv7m_systick",
.version_id = 1,
.minimum_version_id = 1,
.fields = (VMStateField[]) {
VMSTATE_UINT32(control, SysTickState),
VMSTATE_UINT32(reload, SysTickState),
VMSTATE_INT64(tick, SysTickState),
VMSTATE_TIMER_PTR(timer, 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;
}
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)
