qemu

ptimer.h (11769B)

---

 /*
  * 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