qemu/hw/core/ptimer.c
Peter Maydell af2a580f7e ptimer: Remove old ptimer_init_with_bh() API
Now all the users of ptimers have converted to the transaction-based
API, we can remove ptimer_init_with_bh() and all the code paths
that are used only by bottom-half based ptimers, and tidy up the
documentation comments to consider the transaction-based API the
only possibility.

The code changes result from:
 * s->bh no longer exists
 * s->callback is now always non-NULL

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20191025142411.17085-1-peter.maydell@linaro.org
2019-11-11 13:44:16 +00:00

447 lines
13 KiB
C

/*
* General purpose implementation of a simple periodic countdown timer.
*
* Copyright (c) 2007 CodeSourcery.
*
* This code is licensed under the GNU LGPL.
*/
#include "qemu/osdep.h"
#include "qemu/timer.h"
#include "hw/ptimer.h"
#include "migration/vmstate.h"
#include "qemu/host-utils.h"
#include "sysemu/replay.h"
#include "sysemu/qtest.h"
#include "block/aio.h"
#include "sysemu/cpus.h"
#define DELTA_ADJUST 1
#define DELTA_NO_ADJUST -1
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;
uint8_t policy_mask;
QEMUTimer *timer;
ptimer_cb callback;
void *callback_opaque;
/*
* These track whether we're in a transaction block, and if we
* need to do a timer reload when the block finishes. They don't
* need to be migrated because migration can never happen in the
* middle of a transaction block.
*/
bool in_transaction;
bool need_reload;
};
/* Use a bottom-half routine to avoid reentrancy issues. */
static void ptimer_trigger(ptimer_state *s)
{
s->callback(s->callback_opaque);
}
static void ptimer_reload(ptimer_state *s, int delta_adjust)
{
uint32_t period_frac;
uint64_t period;
uint64_t delta;
bool suppress_trigger = false;
/*
* Note that if delta_adjust is 0 then we must be here because of
* a count register write or timer start, not because of timer expiry.
* In that case the policy might require us to suppress the timer trigger
* that we would otherwise generate for a zero delta.
*/
if (delta_adjust == 0 &&
(s->policy_mask & PTIMER_POLICY_TRIGGER_ONLY_ON_DECREMENT)) {
suppress_trigger = true;
}
if (s->delta == 0 && !(s->policy_mask & PTIMER_POLICY_NO_IMMEDIATE_TRIGGER)
&& !suppress_trigger) {
ptimer_trigger(s);
}
/*
* Note that ptimer_trigger() might call the device callback function,
* which can then modify timer state, so we must not cache any fields
* from ptimer_state until after we have called it.
*/
delta = s->delta;
period = s->period;
period_frac = s->period_frac;
if (delta == 0 && !(s->policy_mask & PTIMER_POLICY_NO_IMMEDIATE_RELOAD)) {
delta = s->delta = s->limit;
}
if (s->period == 0) {
if (!qtest_enabled()) {
fprintf(stderr, "Timer with period zero, disabling\n");
}
timer_del(s->timer);
s->enabled = 0;
return;
}
if (s->policy_mask & PTIMER_POLICY_WRAP_AFTER_ONE_PERIOD) {
if (delta_adjust != DELTA_NO_ADJUST) {
delta += delta_adjust;
}
}
if (delta == 0 && (s->policy_mask & PTIMER_POLICY_CONTINUOUS_TRIGGER)) {
if (s->enabled == 1 && s->limit == 0) {
delta = 1;
}
}
if (delta == 0 && (s->policy_mask & PTIMER_POLICY_NO_IMMEDIATE_TRIGGER)) {
if (delta_adjust != DELTA_NO_ADJUST) {
delta = 1;
}
}
if (delta == 0 && (s->policy_mask & PTIMER_POLICY_NO_IMMEDIATE_RELOAD)) {
if (s->enabled == 1 && s->limit != 0) {
delta = 1;
}
}
if (delta == 0) {
if (!qtest_enabled()) {
fprintf(stderr, "Timer with delta zero, disabling\n");
}
timer_del(s->timer);
s->enabled = 0;
return;
}
/*
* 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 (s->enabled == 1 && (delta * period < 10000) && !use_icount) {
period = 10000 / delta;
period_frac = 0;
}
s->last_event = s->next_event;
s->next_event = s->last_event + delta * period;
if (period_frac) {
s->next_event += ((int64_t)period_frac * delta) >> 32;
}
timer_mod(s->timer, s->next_event);
}
static void ptimer_tick(void *opaque)
{
ptimer_state *s = (ptimer_state *)opaque;
bool trigger = true;
/*
* We perform all the tick actions within a begin/commit block
* because the callback function that ptimer_trigger() calls
* might make calls into the ptimer APIs that provoke another
* trigger, and we want that to cause the callback function
* to be called iteratively, not recursively.
*/
ptimer_transaction_begin(s);
if (s->enabled == 2) {
s->delta = 0;
s->enabled = 0;
} else {
int delta_adjust = DELTA_ADJUST;
if (s->delta == 0 || s->limit == 0) {
/* If a "continuous trigger" policy is not used and limit == 0,
we should error out. delta == 0 means that this tick is
caused by a "no immediate reload" policy, so it shouldn't
be adjusted. */
delta_adjust = DELTA_NO_ADJUST;
}
if (!(s->policy_mask & PTIMER_POLICY_NO_IMMEDIATE_TRIGGER)) {
/* Avoid re-trigger on deferred reload if "no immediate trigger"
policy isn't used. */
trigger = (delta_adjust == DELTA_ADJUST);
}
s->delta = s->limit;
ptimer_reload(s, delta_adjust);
}
if (trigger) {
ptimer_trigger(s);
}
ptimer_transaction_commit(s);
}
uint64_t ptimer_get_count(ptimer_state *s)
{
uint64_t counter;
if (s->enabled && s->delta != 0) {
int64_t now = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL);
int64_t next = s->next_event;
int64_t last = s->last_event;
bool expired = (now - next >= 0);
bool oneshot = (s->enabled == 2);
/* Figure out the current counter value. */
if (expired) {
/* Prevent timer underflowing if it should already have
triggered. */
counter = 0;
} else {
uint64_t rem;
uint64_t div;
int clz1, clz2;
int shift;
uint32_t period_frac = s->period_frac;
uint64_t period = s->period;
if (!oneshot && (s->delta * period < 10000) && !use_icount) {
period = 10000 / s->delta;
period_frac = 0;
}
/* 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 = next - now;
div = period;
clz1 = clz64(rem);
clz2 = clz64(div);
shift = clz1 < clz2 ? clz1 : clz2;
rem <<= shift;
div <<= shift;
if (shift >= 32) {
div |= ((uint64_t)period_frac << (shift - 32));
} else {
if (shift != 0)
div |= (period_frac >> (32 - shift));
/* Look at remaining bits of period_frac and round div up if
necessary. */
if ((uint32_t)(period_frac << shift))
div += 1;
}
counter = rem / div;
if (s->policy_mask & PTIMER_POLICY_WRAP_AFTER_ONE_PERIOD) {
/* Before wrapping around, timer should stay with counter = 0
for a one period. */
if (!oneshot && s->delta == s->limit) {
if (now == last) {
/* Counter == delta here, check whether it was
adjusted and if it was, then right now it is
that "one period". */
if (counter == s->limit + DELTA_ADJUST) {
return 0;
}
} else if (counter == s->limit) {
/* Since the counter is rounded down and now != last,
the counter == limit means that delta was adjusted
by +1 and right now it is that adjusted period. */
return 0;
}
}
}
}
if (s->policy_mask & PTIMER_POLICY_NO_COUNTER_ROUND_DOWN) {
/* If now == last then delta == limit, i.e. the counter already
represents the correct value. It would be rounded down a 1ns
later. */
if (now != last) {
counter += 1;
}
}
} else {
counter = s->delta;
}
return counter;
}
void ptimer_set_count(ptimer_state *s, uint64_t count)
{
assert(s->in_transaction);
s->delta = count;
if (s->enabled) {
s->need_reload = true;
}
}
void ptimer_run(ptimer_state *s, int oneshot)
{
bool was_disabled = !s->enabled;
assert(s->in_transaction);
if (was_disabled && s->period == 0) {
if (!qtest_enabled()) {
fprintf(stderr, "Timer with period zero, disabling\n");
}
return;
}
s->enabled = oneshot ? 2 : 1;
if (was_disabled) {
s->need_reload = true;
}
}
/* Pause a timer. Note that this may cause it to "lose" time, even if it
is immediately restarted. */
void ptimer_stop(ptimer_state *s)
{
assert(s->in_transaction);
if (!s->enabled)
return;
s->delta = ptimer_get_count(s);
timer_del(s->timer);
s->enabled = 0;
s->need_reload = false;
}
/* Set counter increment interval in nanoseconds. */
void ptimer_set_period(ptimer_state *s, int64_t period)
{
assert(s->in_transaction);
s->delta = ptimer_get_count(s);
s->period = period;
s->period_frac = 0;
if (s->enabled) {
s->need_reload = true;
}
}
/* Set counter frequency in Hz. */
void ptimer_set_freq(ptimer_state *s, uint32_t freq)
{
assert(s->in_transaction);
s->delta = ptimer_get_count(s);
s->period = 1000000000ll / freq;
s->period_frac = (1000000000ll << 32) / freq;
if (s->enabled) {
s->need_reload = true;
}
}
/* 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)
{
assert(s->in_transaction);
s->limit = limit;
if (reload)
s->delta = limit;
if (s->enabled && reload) {
s->need_reload = true;
}
}
uint64_t ptimer_get_limit(ptimer_state *s)
{
return s->limit;
}
void ptimer_transaction_begin(ptimer_state *s)
{
assert(!s->in_transaction);
s->in_transaction = true;
s->need_reload = false;
}
void ptimer_transaction_commit(ptimer_state *s)
{
assert(s->in_transaction);
/*
* We must loop here because ptimer_reload() can call the callback
* function, which might then update ptimer state in a way that
* means we need to do another reload and possibly another callback.
* A disabled timer never needs reloading (and if we don't check
* this then we loop forever if ptimer_reload() disables the timer).
*/
while (s->need_reload && s->enabled) {
s->need_reload = false;
s->next_event = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL);
ptimer_reload(s, 0);
}
/* Now we've finished reload we can leave the transaction block. */
s->in_transaction = false;
}
const VMStateDescription vmstate_ptimer = {
.name = "ptimer",
.version_id = 1,
.minimum_version_id = 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_PTR(timer, ptimer_state),
VMSTATE_END_OF_LIST()
}
};
ptimer_state *ptimer_init(ptimer_cb callback, void *callback_opaque,
uint8_t policy_mask)
{
ptimer_state *s;
/* The callback function is mandatory. */
assert(callback);
s = g_new0(ptimer_state, 1);
s->timer = timer_new_ns(QEMU_CLOCK_VIRTUAL, ptimer_tick, s);
s->policy_mask = policy_mask;
s->callback = callback;
s->callback_opaque = callback_opaque;
/*
* These two policies are incompatible -- trigger-on-decrement implies
* a timer trigger when the count becomes 0, but no-immediate-trigger
* implies a trigger when the count stops being 0.
*/
assert(!((policy_mask & PTIMER_POLICY_TRIGGER_ONLY_ON_DECREMENT) &&
(policy_mask & PTIMER_POLICY_NO_IMMEDIATE_TRIGGER)));
return s;
}
void ptimer_free(ptimer_state *s)
{
timer_free(s->timer);
g_free(s);
}