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/*
* General purpose implementation of a simple periodic countdown timer.
*
* Copyright (c) 2007 CodeSourcery.
*
* This code is licensed under the GNU LGPL.
*/
#include "hw/hw.h"
#include "qemu/timer.h"
#include "hw/ptimer.h"
#include "qemu/host-utils.h"
struct ptimer_state
{
uint8_t enabled; /* 0 = disabled, 1 = periodic, 2 = oneshot. */
uint64_t limit;
uint64_t delta;
uint32_t period_frac;
int64_t period;
int64_t last_event;
int64_t next_event;
QEMUBH *bh;
QEMUTimer *timer;
};
/* Use a bottom-half routine to avoid reentrancy issues. */
static void ptimer_trigger(ptimer_state *s)
{
if (s->bh) {
qemu_bh_schedule(s->bh);
}
}
static void ptimer_reload(ptimer_state *s)
{
if (s->delta == 0) {
ptimer_trigger(s);
s->delta = s->limit;
}
if (s->delta == 0 || s->period == 0) {
fprintf(stderr, "Timer with period zero, disabling\n");
s->enabled = 0;
return;
}
s->last_event = s->next_event;
s->next_event = s->last_event + s->delta * s->period;
if (s->period_frac) {
s->next_event += ((int64_t)s->period_frac * s->delta) >> 32;
}
timer_mod(s->timer, s->next_event);
}
static void ptimer_tick(void *opaque)
{
ptimer_state *s = (ptimer_state *)opaque;
ptimer_trigger(s);
s->delta = 0;
if (s->enabled == 2) {
s->enabled = 0;
} else {
ptimer_reload(s);
}
}
uint64_t ptimer_get_count(ptimer_state *s)
{
int64_t now;
uint64_t counter;
if (s->enabled) {
now = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL);
/* Figure out the current counter value. */
if (now - s->next_event > 0
|| s->period == 0) {
/* Prevent timer underflowing if it should already have
triggered. */
counter = 0;
} else {
uint64_t rem;
uint64_t div;
int clz1, clz2;
int shift;
/* We need to divide time by period, where time is stored in
rem (64-bit integer) and period is stored in period/period_frac
(64.32 fixed point).
Doing full precision division is hard, so scale values and
do a 64-bit division. The result should be rounded down,
so that the rounding error never causes the timer to go
backwards.
*/
rem = s->next_event - now;
div = s->period;
clz1 = clz64(rem);
clz2 = clz64(div);
shift = clz1 < clz2 ? clz1 : clz2;
rem <<= shift;
div <<= shift;
if (shift >= 32) {
div |= ((uint64_t)s->period_frac << (shift - 32));
} else {
if (shift != 0)
div |= (s->period_frac >> (32 - shift));
/* Look at remaining bits of period_frac and round div up if
necessary. */
if ((uint32_t)(s->period_frac << shift))
div += 1;
}
counter = rem / div;
}
} else {
counter = s->delta;
}
return counter;
}
void ptimer_set_count(ptimer_state *s, uint64_t count)
{
s->delta = count;
if (s->enabled) {
s->next_event = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL);
ptimer_reload(s);
}
}
void ptimer_run(ptimer_state *s, int oneshot)
{
if (s->enabled) {
return;
}
if (s->period == 0) {
fprintf(stderr, "Timer with period zero, disabling\n");
return;
}
s->enabled = oneshot ? 2 : 1;
s->next_event = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL);
ptimer_reload(s);
}
/* Pause a timer. Note that this may cause it to "lose" time, even if it
is immediately restarted. */
void ptimer_stop(ptimer_state *s)
{
if (!s->enabled)
return;
s->delta = ptimer_get_count(s);
timer_del(s->timer);
s->enabled = 0;
}
/* Set counter increment interval in nanoseconds. */
void ptimer_set_period(ptimer_state *s, int64_t period)
{
s->period = period;
s->period_frac = 0;
if (s->enabled) {
s->next_event = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL);
ptimer_reload(s);
}
}
/* Set counter frequency in Hz. */
void ptimer_set_freq(ptimer_state *s, uint32_t freq)
{
s->period = 1000000000ll / freq;
s->period_frac = (1000000000ll << 32) / freq;
if (s->enabled) {
s->next_event = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL);
ptimer_reload(s);
}
}
/* Set the initial countdown value. If reload is nonzero then also set
count = limit. */
void ptimer_set_limit(ptimer_state *s, uint64_t limit, int reload)
{
/*
* Artificially limit timeout rate to something
* achievable under QEMU. Otherwise, QEMU spends all
* its time generating timer interrupts, and there
* is no forward progress.
* About ten microseconds is the fastest that really works
* on the current generation of host machines.
*/
if (limit * s->period < 10000 && s->period) {
limit = 10000 / s->period;
}
s->limit = limit;
if (reload)
s->delta = limit;
if (s->enabled && reload) {
s->next_event = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL);
ptimer_reload(s);
}
}
const VMStateDescription vmstate_ptimer = {
.name = "ptimer",
.version_id = 1,
.minimum_version_id = 1,
.minimum_version_id_old = 1,
.fields = (VMStateField[]) {
VMSTATE_UINT8(enabled, ptimer_state),
VMSTATE_UINT64(limit, ptimer_state),
VMSTATE_UINT64(delta, ptimer_state),
VMSTATE_UINT32(period_frac, ptimer_state),
VMSTATE_INT64(period, ptimer_state),
VMSTATE_INT64(last_event, ptimer_state),
VMSTATE_INT64(next_event, ptimer_state),
VMSTATE_TIMER(timer, ptimer_state),
VMSTATE_END_OF_LIST()
}
};
ptimer_state *ptimer_init(QEMUBH *bh)
{
ptimer_state *s;
s = (ptimer_state *)g_malloc0(sizeof(ptimer_state));
s->bh = bh;
s->timer = timer_new_ns(QEMU_CLOCK_VIRTUAL, ptimer_tick, s);
return s;
}
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