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Diffstat (limited to 'include/hw/ptimer.h')
| -rw-r--r-- | include/hw/ptimer.h | 301 |
1 files changed, 301 insertions, 0 deletions
diff --git a/include/hw/ptimer.h b/include/hw/ptimer.h new file mode 100644 index 000000000..c44321847 --- /dev/null +++ b/include/hw/ptimer.h @@ -0,0 +1,301 @@ +/* + * 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 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). + */ +#define PTIMER_POLICY_DEFAULT 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 |