1/*
2 * General purpose implementation of a simple periodic countdown timer.
3 *
4 * Copyright (c) 2007 CodeSourcery.
5 *
6 * This code is licensed under the GNU LGPL.
7 */
8#ifndef PTIMER_H
9#define PTIMER_H
10
11#include "qemu/timer.h"
12
13/* The ptimer API implements a simple periodic countdown timer.
14 * The countdown timer has a value (which can be read and written via
15 * ptimer_get_count() and ptimer_set_count()). When it is enabled
16 * using ptimer_run(), the value will count downwards at the frequency
17 * which has been configured using ptimer_set_period() or ptimer_set_freq().
18 * When it reaches zero it will trigger a QEMU bottom half handler, and
19 * can be set to either reload itself from a specified limit value
20 * and keep counting down, or to stop (as a one-shot timer).
21 *
22 * Forgetting to set the period/frequency (or setting it to zero) is a
23 * bug in the QEMU device and will cause warning messages to be printed
24 * to stderr when the guest attempts to enable the timer.
25 */
26
27/* The default ptimer policy retains backward compatibility with the legacy
28 * timers. Custom policies are adjusting the default one. Consider providing
29 * a correct policy for your timer.
30 *
31 * The rough edges of the default policy:
32 * - Starting to run with a period = 0 emits error message and stops the
33 * timer without a trigger.
34 *
35 * - Setting period to 0 of the running timer emits error message and
36 * stops the timer without a trigger.
37 *
38 * - Starting to run with counter = 0 or setting it to "0" while timer
39 * is running causes a trigger and reloads counter with a limit value.
40 * If limit = 0, ptimer emits error message and stops the timer.
41 *
42 * - Counter value of the running timer is one less than the actual value.
43 *
44 * - Changing period/frequency of the running timer loses time elapsed
45 * since the last period, effectively restarting the timer with a
46 * counter = counter value at the moment of change (.i.e. one less).
47 */
48#define PTIMER_POLICY_DEFAULT 0
49
50/* Periodic timer counter stays with "0" for a one period before wrapping
51 * around. */
52#define PTIMER_POLICY_WRAP_AFTER_ONE_PERIOD (1 << 0)
53
54/* Running periodic timer that has counter = limit = 0 would continuously
55 * re-trigger every period. */
56#define PTIMER_POLICY_CONTINUOUS_TRIGGER (1 << 1)
57
58/* Starting to run with/setting counter to "0" won't trigger immediately,
59 * but after a one period for both oneshot and periodic modes. */
60#define PTIMER_POLICY_NO_IMMEDIATE_TRIGGER (1 << 2)
61
62/* Starting to run with/setting counter to "0" won't re-load counter
63 * immediately, but after a one period. */
64#define PTIMER_POLICY_NO_IMMEDIATE_RELOAD (1 << 3)
65
66/* Make counter value of the running timer represent the actual value and
67 * not the one less. */
68#define PTIMER_POLICY_NO_COUNTER_ROUND_DOWN (1 << 4)
69
70/*
71 * Starting to run with a zero counter, or setting the counter to "0" via
72 * ptimer_set_count() or ptimer_set_limit() will not trigger the timer
73 * (though it will cause a reload). Only a counter decrement to "0"
74 * will cause a trigger. Not compatible with NO_IMMEDIATE_TRIGGER;
75 * ptimer_init() will assert() that you don't set both.
76 */
77#define PTIMER_POLICY_TRIGGER_ONLY_ON_DECREMENT (1 << 5)
78
79/* ptimer.c */
80typedef struct ptimer_state ptimer_state;
81typedef void (*ptimer_cb)(void *opaque);
82
83/**
84 * ptimer_init - Allocate and return a new ptimer
85 * @bh: QEMU bottom half which is run on timer expiry
86 * @policy: PTIMER_POLICY_* bits specifying behaviour
87 *
88 * The ptimer returned must be freed using ptimer_free().
89 * The ptimer takes ownership of @bh and will delete it
90 * when the ptimer is eventually freed.
91 */
92ptimer_state *ptimer_init(QEMUBH *bh, uint8_t policy_mask);
93
94/**
95 * ptimer_free - Free a ptimer
96 * @s: timer to free
97 *
98 * Free a ptimer created using ptimer_init() (including
99 * deleting the bottom half which it is using).
100 */
101void ptimer_free(ptimer_state *s);
102
103/**
104 * ptimer_set_period - Set counter increment interval in nanoseconds
105 * @s: ptimer to configure
106 * @period: period of the counter in nanoseconds
107 *
108 * Note that if your counter behaviour is specified as having a
109 * particular frequency rather than a period then ptimer_set_freq()
110 * may be more appropriate.
111 */
112void ptimer_set_period(ptimer_state *s, int64_t period);
113
114/**
115 * ptimer_set_freq - Set counter frequency in Hz
116 * @s: ptimer to configure
117 * @freq: counter frequency in Hz
118 *
119 * This does the same thing as ptimer_set_period(), so you only
120 * need to call one of them. If the counter behaviour is specified
121 * as setting the frequency then this function is more appropriate,
122 * because it allows specifying an effective period which is
123 * precise to fractions of a nanosecond, avoiding rounding errors.
124 */
125void ptimer_set_freq(ptimer_state *s, uint32_t freq);
126
127/**
128 * ptimer_get_limit - Get the configured limit of the ptimer
129 * @s: ptimer to query
130 *
131 * This function returns the current limit (reload) value
132 * of the down-counter; that is, the value which it will be
133 * reset to when it hits zero.
134 *
135 * Generally timer devices using ptimers should be able to keep
136 * their reload register state inside the ptimer using the get
137 * and set limit functions rather than needing to also track it
138 * in their own state structure.
139 */
140uint64_t ptimer_get_limit(ptimer_state *s);
141
142/**
143 * ptimer_set_limit - Set the limit of the ptimer
144 * @s: ptimer
145 * @limit: initial countdown value
146 * @reload: if nonzero, then reset the counter to the new limit
147 *
148 * Set the limit value of the down-counter. The @reload flag can
149 * be used to emulate the behaviour of timers which immediately
150 * reload the counter when their reload register is written to.
151 */
152void ptimer_set_limit(ptimer_state *s, uint64_t limit, int reload);
153
154/**
155 * ptimer_get_count - Get the current value of the ptimer
156 * @s: ptimer
157 *
158 * Return the current value of the down-counter. This will
159 * return the correct value whether the counter is enabled or
160 * disabled.
161 */
162uint64_t ptimer_get_count(ptimer_state *s);
163
164/**
165 * ptimer_set_count - Set the current value of the ptimer
166 * @s: ptimer
167 * @count: count value to set
168 *
169 * Set the value of the down-counter. If the counter is currently
170 * enabled this will arrange for a timer callback at the appropriate
171 * point in the future.
172 */
173void ptimer_set_count(ptimer_state *s, uint64_t count);
174
175/**
176 * ptimer_run - Start a ptimer counting
177 * @s: ptimer
178 * @oneshot: non-zero if this timer should only count down once
179 *
180 * Start a ptimer counting down; when it reaches zero the bottom half
181 * passed to ptimer_init() will be invoked. If the @oneshot argument is zero,
182 * the counter value will then be reloaded from the limit and it will
183 * start counting down again. If @oneshot is non-zero, then the counter
184 * will disable itself when it reaches zero.
185 */
186void ptimer_run(ptimer_state *s, int oneshot);
187
188/**
189 * ptimer_stop - Stop a ptimer counting
190 * @s: ptimer
191 *
192 * Pause a timer (the count stays at its current value until ptimer_run()
193 * is called to start it counting again).
194 *
195 * Note that this can cause it to "lose" time, even if it is immediately
196 * restarted.
197 */
198void ptimer_stop(ptimer_state *s);
199
200extern const VMStateDescription vmstate_ptimer;
201
202#define VMSTATE_PTIMER(_field, _state) \
203 VMSTATE_STRUCT_POINTER_V(_field, _state, 1, vmstate_ptimer, ptimer_state)
204
205#define VMSTATE_PTIMER_ARRAY(_f, _s, _n) \
206 VMSTATE_ARRAY_OF_POINTER_TO_STRUCT(_f, _s, _n, 0, \
207 vmstate_ptimer, ptimer_state)
208
209#endif
210