Merge remote-tracking branch 'remotes/vivier2/tags/trivial-branch-for-5.2-pull-reques...
[qemu.git] / include / hw / ptimer.h
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 /*
14 * The ptimer API implements a simple periodic countdown timer.
15 * The countdown timer has a value (which can be read and written via
16 * ptimer_get_count() and ptimer_set_count()). When it is enabled
17 * using ptimer_run(), the value will count downwards at the frequency
18 * which has been configured using ptimer_set_period() or ptimer_set_freq().
19 * When it reaches zero it will trigger a callback function, and
20 * can be set to either reload itself from a specified limit value
21 * and keep counting down, or to stop (as a one-shot timer).
22 *
23 * A transaction-based API is used for modifying ptimer state: all calls
24 * to functions which modify ptimer state must be between matched calls to
25 * ptimer_transaction_begin() and ptimer_transaction_commit().
26 * When ptimer_transaction_commit() is called it will evaluate the state
27 * of the timer after all the changes in the transaction, and call the
28 * callback if necessary. (See the ptimer_init() documentation for the full
29 * list of state-modifying functions and detailed semantics of the callback.)
30 *
31 * Forgetting to set the period/frequency (or setting it to zero) is a
32 * bug in the QEMU device and will cause warning messages to be printed
33 * to stderr when the guest attempts to enable the timer.
34 */
35
36 /* The default ptimer policy retains backward compatibility with the legacy
37 * timers. Custom policies are adjusting the default one. Consider providing
38 * a correct policy for your timer.
39 *
40 * The rough edges of the default policy:
41 * - Starting to run with a period = 0 emits error message and stops the
42 * timer without a trigger.
43 *
44 * - Setting period to 0 of the running timer emits error message and
45 * stops the timer without a trigger.
46 *
47 * - Starting to run with counter = 0 or setting it to "0" while timer
48 * is running causes a trigger and reloads counter with a limit value.
49 * If limit = 0, ptimer emits error message and stops the timer.
50 *
51 * - Counter value of the running timer is one less than the actual value.
52 *
53 * - Changing period/frequency of the running timer loses time elapsed
54 * since the last period, effectively restarting the timer with a
55 * counter = counter value at the moment of change (.i.e. one less).
56 */
57 #define PTIMER_POLICY_DEFAULT 0
58
59 /* Periodic timer counter stays with "0" for a one period before wrapping
60 * around. */
61 #define PTIMER_POLICY_WRAP_AFTER_ONE_PERIOD (1 << 0)
62
63 /* Running periodic timer that has counter = limit = 0 would continuously
64 * re-trigger every period. */
65 #define PTIMER_POLICY_CONTINUOUS_TRIGGER (1 << 1)
66
67 /* Starting to run with/setting counter to "0" won't trigger immediately,
68 * but after a one period for both oneshot and periodic modes. */
69 #define PTIMER_POLICY_NO_IMMEDIATE_TRIGGER (1 << 2)
70
71 /* Starting to run with/setting counter to "0" won't re-load counter
72 * immediately, but after a one period. */
73 #define PTIMER_POLICY_NO_IMMEDIATE_RELOAD (1 << 3)
74
75 /* Make counter value of the running timer represent the actual value and
76 * not the one less. */
77 #define PTIMER_POLICY_NO_COUNTER_ROUND_DOWN (1 << 4)
78
79 /*
80 * Starting to run with a zero counter, or setting the counter to "0" via
81 * ptimer_set_count() or ptimer_set_limit() will not trigger the timer
82 * (though it will cause a reload). Only a counter decrement to "0"
83 * will cause a trigger. Not compatible with NO_IMMEDIATE_TRIGGER;
84 * ptimer_init() will assert() that you don't set both.
85 */
86 #define PTIMER_POLICY_TRIGGER_ONLY_ON_DECREMENT (1 << 5)
87
88 /* ptimer.c */
89 typedef struct ptimer_state ptimer_state;
90 typedef void (*ptimer_cb)(void *opaque);
91
92 /**
93 * ptimer_init - Allocate and return a new ptimer
94 * @callback: function to call on ptimer expiry
95 * @callback_opaque: opaque pointer passed to @callback
96 * @policy: PTIMER_POLICY_* bits specifying behaviour
97 *
98 * The ptimer returned must be freed using ptimer_free().
99 *
100 * If a ptimer is created using this API then will use the
101 * transaction-based API for modifying ptimer state: all calls
102 * to functions which modify ptimer state:
103 * - ptimer_set_period()
104 * - ptimer_set_freq()
105 * - ptimer_set_limit()
106 * - ptimer_set_count()
107 * - ptimer_run()
108 * - ptimer_stop()
109 * must be between matched calls to ptimer_transaction_begin()
110 * and ptimer_transaction_commit(). When ptimer_transaction_commit()
111 * is called it will evaluate the state of the timer after all the
112 * changes in the transaction, and call the callback if necessary.
113 *
114 * The callback function is always called from within a transaction
115 * begin/commit block, so the callback should not call the
116 * ptimer_transaction_begin() function itself. If the callback changes
117 * the ptimer state such that another ptimer expiry is triggered, then
118 * the callback will be called a second time after the first call returns.
119 */
120 ptimer_state *ptimer_init(ptimer_cb callback,
121 void *callback_opaque,
122 uint8_t policy_mask);
123
124 /**
125 * ptimer_free - Free a ptimer
126 * @s: timer to free
127 *
128 * Free a ptimer created using ptimer_init().
129 */
130 void ptimer_free(ptimer_state *s);
131
132 /**
133 * ptimer_transaction_begin() - Start a ptimer modification transaction
134 *
135 * This function must be called before making any calls to functions
136 * which modify the ptimer's state (see the ptimer_init() documentation
137 * for a list of these), and must always have a matched call to
138 * ptimer_transaction_commit().
139 * It is an error to call this function for a BH-based ptimer;
140 * attempting to do this will trigger an assert.
141 */
142 void ptimer_transaction_begin(ptimer_state *s);
143
144 /**
145 * ptimer_transaction_commit() - Commit a ptimer modification transaction
146 *
147 * This function must be called after calls to functions which modify
148 * the ptimer's state, and completes the update of the ptimer. If the
149 * ptimer state now means that we should trigger the timer expiry
150 * callback, it will be called directly.
151 */
152 void ptimer_transaction_commit(ptimer_state *s);
153
154 /**
155 * ptimer_set_period - Set counter increment interval in nanoseconds
156 * @s: ptimer to configure
157 * @period: period of the counter in nanoseconds
158 *
159 * Note that if your counter behaviour is specified as having a
160 * particular frequency rather than a period then ptimer_set_freq()
161 * may be more appropriate.
162 *
163 * This function will assert if it is called outside a
164 * ptimer_transaction_begin/commit block.
165 */
166 void ptimer_set_period(ptimer_state *s, int64_t period);
167
168 /**
169 * ptimer_set_freq - Set counter frequency in Hz
170 * @s: ptimer to configure
171 * @freq: counter frequency in Hz
172 *
173 * This does the same thing as ptimer_set_period(), so you only
174 * need to call one of them. If the counter behaviour is specified
175 * as setting the frequency then this function is more appropriate,
176 * because it allows specifying an effective period which is
177 * precise to fractions of a nanosecond, avoiding rounding errors.
178 *
179 * This function will assert if it is called outside a
180 * ptimer_transaction_begin/commit block.
181 */
182 void ptimer_set_freq(ptimer_state *s, uint32_t freq);
183
184 /**
185 * ptimer_get_limit - Get the configured limit of the ptimer
186 * @s: ptimer to query
187 *
188 * This function returns the current limit (reload) value
189 * of the down-counter; that is, the value which it will be
190 * reset to when it hits zero.
191 *
192 * Generally timer devices using ptimers should be able to keep
193 * their reload register state inside the ptimer using the get
194 * and set limit functions rather than needing to also track it
195 * in their own state structure.
196 */
197 uint64_t ptimer_get_limit(ptimer_state *s);
198
199 /**
200 * ptimer_set_limit - Set the limit of the ptimer
201 * @s: ptimer
202 * @limit: initial countdown value
203 * @reload: if nonzero, then reset the counter to the new limit
204 *
205 * Set the limit value of the down-counter. The @reload flag can
206 * be used to emulate the behaviour of timers which immediately
207 * reload the counter when their reload register is written to.
208 *
209 * This function will assert if it is called outside a
210 * ptimer_transaction_begin/commit block.
211 */
212 void ptimer_set_limit(ptimer_state *s, uint64_t limit, int reload);
213
214 /**
215 * ptimer_get_count - Get the current value of the ptimer
216 * @s: ptimer
217 *
218 * Return the current value of the down-counter. This will
219 * return the correct value whether the counter is enabled or
220 * disabled.
221 */
222 uint64_t ptimer_get_count(ptimer_state *s);
223
224 /**
225 * ptimer_set_count - Set the current value of the ptimer
226 * @s: ptimer
227 * @count: count value to set
228 *
229 * Set the value of the down-counter. If the counter is currently
230 * enabled this will arrange for a timer callback at the appropriate
231 * point in the future.
232 *
233 * This function will assert if it is called outside a
234 * ptimer_transaction_begin/commit block.
235 */
236 void ptimer_set_count(ptimer_state *s, uint64_t count);
237
238 /**
239 * ptimer_run - Start a ptimer counting
240 * @s: ptimer
241 * @oneshot: non-zero if this timer should only count down once
242 *
243 * Start a ptimer counting down; when it reaches zero the callback function
244 * passed to ptimer_init() will be invoked.
245 * If the @oneshot argument is zero,
246 * the counter value will then be reloaded from the limit and it will
247 * start counting down again. If @oneshot is non-zero, then the counter
248 * will disable itself when it reaches zero.
249 *
250 * This function will assert if it is called outside a
251 * ptimer_transaction_begin/commit block.
252 */
253 void ptimer_run(ptimer_state *s, int oneshot);
254
255 /**
256 * ptimer_stop - Stop a ptimer counting
257 * @s: ptimer
258 *
259 * Pause a timer (the count stays at its current value until ptimer_run()
260 * is called to start it counting again).
261 *
262 * Note that this can cause it to "lose" time, even if it is immediately
263 * restarted.
264 *
265 * This function will assert if it is called outside a
266 * ptimer_transaction_begin/commit block.
267 */
268 void ptimer_stop(ptimer_state *s);
269
270 extern const VMStateDescription vmstate_ptimer;
271
272 #define VMSTATE_PTIMER(_field, _state) \
273 VMSTATE_STRUCT_POINTER_V(_field, _state, 1, vmstate_ptimer, ptimer_state)
274
275 #define VMSTATE_PTIMER_ARRAY(_f, _s, _n) \
276 VMSTATE_ARRAY_OF_POINTER_TO_STRUCT(_f, _s, _n, 0, \
277 vmstate_ptimer, ptimer_state)
278
279 #endif