blob: 0731d9aef1977087c35f95071c80d9786107af8f [file] [log] [blame]
* General purpose implementation of a simple periodic countdown timer.
* Copyright (c) 2007 CodeSourcery.
* This code is licensed under the GNU LGPL.
#ifndef PTIMER_H
#define PTIMER_H
#include "qemu-common.h"
#include "qemu/timer.h"
#include "migration/vmstate.h"
/* The ptimer API implements a simple periodic countdown timer.
* The countdown timer has a value (which can be read and written via
* ptimer_get_count() and ptimer_set_count()). When it is enabled
* using ptimer_run(), the value will count downwards at the frequency
* which has been configured using ptimer_set_period() or ptimer_set_freq().
* When it reaches zero it will trigger a QEMU bottom half handler, and
* can be set to either reload itself from a specified limit value
* and keep counting down, or to stop (as a one-shot timer).
* Forgetting to set the period/frequency (or setting it to zero) is a
* bug in the QEMU device and will cause warning messages to be printed
* to stderr when the guest attempts to enable the timer.
/* The default ptimer policy retains backward compatibility with the legacy
* timers. Custom policies are adjusting the default one. Consider providing
* a correct policy for your timer.
* The rough edges of the default policy:
* - Starting to run with a period = 0 emits error message and stops the
* timer without a trigger.
* - Setting period to 0 of the running timer emits error message and
* stops the timer without a trigger.
* - Starting to run with counter = 0 or setting it to "0" while timer
* is running causes a trigger and reloads counter with a limit value.
* If limit = 0, ptimer emits error message and stops the timer.
* - Counter value of the running timer is one less than the actual value.
* - Changing period/frequency of the running timer loses time elapsed
* since the last period, effectively restarting the timer with a
* counter = counter value at the moment of change (.i.e. one less).
/* Periodic timer counter stays with "0" for a one period before wrapping
* around. */
/* Running periodic timer that has counter = limit = 0 would continuously
* re-trigger every period. */
/* Starting to run with/setting counter to "0" won't trigger immediately,
* but after a one period for both oneshot and periodic modes. */
/* Starting to run with/setting counter to "0" won't re-load counter
* immediately, but after a one period. */
/* Make counter value of the running timer represent the actual value and
* not the one less. */
* Starting to run with a zero counter, or setting the counter to "0" via
* ptimer_set_count() or ptimer_set_limit() will not trigger the timer
* (though it will cause a reload). Only a counter decrement to "0"
* will cause a trigger. Not compatible with NO_IMMEDIATE_TRIGGER;
* ptimer_init() will assert() that you don't set both.
/* ptimer.c */
typedef struct ptimer_state ptimer_state;
typedef void (*ptimer_cb)(void *opaque);
* ptimer_init - Allocate and return a new ptimer
* @bh: QEMU bottom half which is run on timer expiry
* @policy: PTIMER_POLICY_* bits specifying behaviour
* The ptimer returned must be freed using ptimer_free().
* The ptimer takes ownership of @bh and will delete it
* when the ptimer is eventually freed.
ptimer_state *ptimer_init(QEMUBH *bh, uint8_t policy_mask);
* ptimer_free - Free a ptimer
* @s: timer to free
* Free a ptimer created using ptimer_init() (including
* deleting the bottom half which it is using).
void ptimer_free(ptimer_state *s);
* ptimer_set_period - Set counter increment interval in nanoseconds
* @s: ptimer to configure
* @period: period of the counter in nanoseconds
* Note that if your counter behaviour is specified as having a
* particular frequency rather than a period then ptimer_set_freq()
* may be more appropriate.
void ptimer_set_period(ptimer_state *s, int64_t period);
* ptimer_set_freq - Set counter frequency in Hz
* @s: ptimer to configure
* @freq: counter frequency in Hz
* This does the same thing as ptimer_set_period(), so you only
* need to call one of them. If the counter behaviour is specified
* as setting the frequency then this function is more appropriate,
* because it allows specifying an effective period which is
* precise to fractions of a nanosecond, avoiding rounding errors.
void ptimer_set_freq(ptimer_state *s, uint32_t freq);
* ptimer_get_limit - Get the configured limit of the ptimer
* @s: ptimer to query
* This function returns the current limit (reload) value
* of the down-counter; that is, the value which it will be
* reset to when it hits zero.
* Generally timer devices using ptimers should be able to keep
* their reload register state inside the ptimer using the get
* and set limit functions rather than needing to also track it
* in their own state structure.
uint64_t ptimer_get_limit(ptimer_state *s);
* ptimer_set_limit - Set the limit of the ptimer
* @s: ptimer
* @limit: initial countdown value
* @reload: if nonzero, then reset the counter to the new limit
* Set the limit value of the down-counter. The @reload flag can
* be used to emulate the behaviour of timers which immediately
* reload the counter when their reload register is written to.
void ptimer_set_limit(ptimer_state *s, uint64_t limit, int reload);
* ptimer_get_count - Get the current value of the ptimer
* @s: ptimer
* Return the current value of the down-counter. This will
* return the correct value whether the counter is enabled or
* disabled.
uint64_t ptimer_get_count(ptimer_state *s);
* ptimer_set_count - Set the current value of the ptimer
* @s: ptimer
* @count: count value to set
* Set the value of the down-counter. If the counter is currently
* enabled this will arrange for a timer callback at the appropriate
* point in the future.
void ptimer_set_count(ptimer_state *s, uint64_t count);
* ptimer_run - Start a ptimer counting
* @s: ptimer
* @oneshot: non-zero if this timer should only count down once
* Start a ptimer counting down; when it reaches zero the bottom half
* passed to ptimer_init() will be invoked. If the @oneshot argument is zero,
* the counter value will then be reloaded from the limit and it will
* start counting down again. If @oneshot is non-zero, then the counter
* will disable itself when it reaches zero.
void ptimer_run(ptimer_state *s, int oneshot);
* ptimer_stop - Stop a ptimer counting
* @s: ptimer
* Pause a timer (the count stays at its current value until ptimer_run()
* is called to start it counting again).
* Note that this can cause it to "lose" time, even if it is immediately
* restarted.
void ptimer_stop(ptimer_state *s);
extern const VMStateDescription vmstate_ptimer;
#define VMSTATE_PTIMER(_field, _state) \
VMSTATE_STRUCT_POINTER_V(_field, _state, 1, vmstate_ptimer, ptimer_state)
#define VMSTATE_PTIMER_ARRAY(_f, _s, _n) \
vmstate_ptimer, ptimer_state)