/*
* 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/timer.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 callback function, 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).
*
* A transaction-based API is used for modifying ptimer state: all calls
* to functions which modify ptimer state must be between matched calls to
* ptimer_transaction_begin() and ptimer_transaction_commit().
* When ptimer_transaction_commit() is called it will evaluate the state
* of the timer after all the changes in the transaction, and call the
* callback if necessary. (See the ptimer_init() documentation for the full
* list of state-modifying functions and detailed semantics of the callback.)
*
* 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 'legacy' ptimer policy retains backward compatibility with the
* traditional ptimer behaviour from before policy flags were introduced.
* It has several weird behaviours which don't match typical hardware
* timer behaviour. For a new device using ptimers, you should not
* use PTIMER_POLICY_LEGACY, but instead check the actual behaviour
* that you need and specify the right set of policy flags to get that.
*
* If you are overhauling an existing device that uses PTIMER_POLICY_LEGACY
* and are in a position to check or test the real hardware behaviour,
* consider updating it to specify the right policy flags.
*
* 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).
*/
#define PTIMER_POLICY_LEGACY 0
/* Periodic timer counter stays with "0" for a one period before wrapping
* around. */
#define PTIMER_POLICY_WRAP_AFTER_ONE_PERIOD (1 << 0)
/* Running periodic timer that has counter = limit = 0 would continuously
* re-trigger every period. */
#define PTIMER_POLICY_CONTINUOUS_TRIGGER (1 << 1)
/* Starting to run with/setting counter to "0" won't trigger immediately,
* but after a one period for both oneshot and periodic modes. */
#define PTIMER_POLICY_NO_IMMEDIATE_TRIGGER (1 << 2)
/* Starting to run with/setting counter to "0" won't re-load counter
* immediately, but after a one period. */
#define PTIMER_POLICY_NO_IMMEDIATE_RELOAD (1 << 3)
/* Make counter value of the running timer represent the actual value and
* not the one less. */
#define PTIMER_POLICY_NO_COUNTER_ROUND_DOWN (1 << 4)
/*
* 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.
*/
#define PTIMER_POLICY_TRIGGER_ONLY_ON_DECREMENT (1 << 5)
/* ptimer.c */
typedef struct ptimer_state ptimer_state;
typedef void (*ptimer_cb)(void *opaque);
/**
* ptimer_init - Allocate and return a new ptimer
* @callback: function to call on ptimer expiry
* @callback_opaque: opaque pointer passed to @callback
* @policy: PTIMER_POLICY_* bits specifying behaviour
*
* The ptimer returned must be freed using ptimer_free().
*
* If a ptimer is created using this API then will use the
* transaction-based API for modifying ptimer state: all calls
* to functions which modify ptimer state:
* - ptimer_set_period()
* - ptimer_set_freq()
* - ptimer_set_limit()
* - ptimer_set_count()
* - ptimer_run()
* - ptimer_stop()
* must be between matched calls to ptimer_transaction_begin()
* and ptimer_transaction_commit(). When ptimer_transaction_commit()
* is called it will evaluate the state of the timer after all the
* changes in the transaction, and call the callback if necessary.
*
* The callback function is always called from within a transaction
* begin/commit block, so the callback should not call the
* ptimer_transaction_begin() function itself. If the callback changes
* the ptimer state such that another ptimer expiry is triggered, then
* the callback will be called a second time after the first call returns.
*/
ptimer_state *ptimer_init(ptimer_cb callback,
void *callback_opaque,
uint8_t policy_mask);
/**
* ptimer_free - Free a ptimer
* @s: timer to free
*
* Free a ptimer created using ptimer_init().
*/
void ptimer_free(ptimer_state *s);
/**
* ptimer_transaction_begin() - Start a ptimer modification transaction
*
* This function must be called before making any calls to functions
* which modify the ptimer's state (see the ptimer_init() documentation
* for a list of these), and must always have a matched call to
* ptimer_transaction_commit().
* It is an error to call this function for a BH-based ptimer;
* attempting to do this will trigger an assert.
*/
void ptimer_transaction_begin(ptimer_state *s);
/**
* ptimer_transaction_commit() - Commit a ptimer modification transaction
*
* This function must be called after calls to functions which modify
* the ptimer's state, and completes the update of the ptimer. If the
* ptimer state now means that we should trigger the timer expiry
* callback, it will be called directly.
*/
void ptimer_transaction_commit(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.
*
* This function will assert if it is called outside a
* ptimer_transaction_begin/commit block.
*/
void ptimer_set_period(ptimer_state *s, int64_t period);
/**
* ptimer_set_period_from_clock - Set counter increment from a Clock
* @s: ptimer to configure
* @clk: pointer to Clock object to take period from
* @divisor: value to scale the clock frequency down by
*
* If the ptimer is being driven from a Clock, this is the preferred
* way to tell the ptimer about the period, because it avoids any
* possible rounding errors that might happen if the internal
* representation of the Clock period was converted to either a period
* in ns or a frequency in Hz.
*
* If the ptimer should run at the same frequency as the clock,
* pass 1 as the @divisor; if the ptimer should run at half the
* frequency, pass 2, and so on.
*
* This function will assert if it is called outside a
* ptimer_transaction_begin/commit block.
*/
void ptimer_set_period_from_clock(ptimer_state *s, const Clock *clock,
unsigned int divisor);
/**
* 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.
*
* This function will assert if it is called outside a
* ptimer_transaction_begin/commit block.
*/
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.
*
* This function will assert if it is called outside a
* ptimer_transaction_begin/commit block.
*/
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.
*
* This function will assert if it is called outside a
* ptimer_transaction_begin/commit block.
*/
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 callback function
* 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.
*
* This function will assert if it is called outside a
* ptimer_transaction_begin/commit block.
*/
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.
*
* This function will assert if it is called outside a
* ptimer_transaction_begin/commit block.
*/
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_ARRAY_OF_POINTER_TO_STRUCT(_f, _s, _n, 0, \
vmstate_ptimer, ptimer_state)
#endif
