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49d4d9b6 PB |
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 | ||
1de7afc9 | 11 | #include "qemu/timer.h" |
49d4d9b6 | 12 | |
af2a580f PM |
13 | /* |
14 | * The ptimer API implements a simple periodic countdown timer. | |
a7a305ae PM |
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(). | |
af2a580f | 19 | * When it reaches zero it will trigger a callback function, and |
a7a305ae PM |
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 | * | |
af2a580f PM |
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 | * | |
a7a305ae PM |
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 | ||
9598c1bb PM |
36 | /* |
37 | * The 'legacy' ptimer policy retains backward compatibility with the | |
38 | * traditional ptimer behaviour from before policy flags were introduced. | |
39 | * It has several weird behaviours which don't match typical hardware | |
40 | * timer behaviour. For a new device using ptimers, you should not | |
41 | * use PTIMER_POLICY_LEGACY, but instead check the actual behaviour | |
42 | * that you need and specify the right set of policy flags to get that. | |
43 | * | |
44 | * If you are overhauling an existing device that uses PTIMER_POLICY_LEGACY | |
45 | * and are in a position to check or test the real hardware behaviour, | |
46 | * consider updating it to specify the right policy flags. | |
e7ea81c3 DO |
47 | * |
48 | * The rough edges of the default policy: | |
49 | * - Starting to run with a period = 0 emits error message and stops the | |
50 | * timer without a trigger. | |
51 | * | |
52 | * - Setting period to 0 of the running timer emits error message and | |
53 | * stops the timer without a trigger. | |
54 | * | |
55 | * - Starting to run with counter = 0 or setting it to "0" while timer | |
56 | * is running causes a trigger and reloads counter with a limit value. | |
57 | * If limit = 0, ptimer emits error message and stops the timer. | |
58 | * | |
59 | * - Counter value of the running timer is one less than the actual value. | |
60 | * | |
61 | * - Changing period/frequency of the running timer loses time elapsed | |
62 | * since the last period, effectively restarting the timer with a | |
63 | * counter = counter value at the moment of change (.i.e. one less). | |
64 | */ | |
9598c1bb | 65 | #define PTIMER_POLICY_LEGACY 0 |
e7ea81c3 | 66 | |
2b5c0322 DO |
67 | /* Periodic timer counter stays with "0" for a one period before wrapping |
68 | * around. */ | |
69 | #define PTIMER_POLICY_WRAP_AFTER_ONE_PERIOD (1 << 0) | |
70 | ||
ef0a9984 DO |
71 | /* Running periodic timer that has counter = limit = 0 would continuously |
72 | * re-trigger every period. */ | |
73 | #define PTIMER_POLICY_CONTINUOUS_TRIGGER (1 << 1) | |
74 | ||
22471b8a DO |
75 | /* Starting to run with/setting counter to "0" won't trigger immediately, |
76 | * but after a one period for both oneshot and periodic modes. */ | |
77 | #define PTIMER_POLICY_NO_IMMEDIATE_TRIGGER (1 << 2) | |
78 | ||
3f6e6a13 DO |
79 | /* Starting to run with/setting counter to "0" won't re-load counter |
80 | * immediately, but after a one period. */ | |
81 | #define PTIMER_POLICY_NO_IMMEDIATE_RELOAD (1 << 3) | |
82 | ||
5580ea45 DO |
83 | /* Make counter value of the running timer represent the actual value and |
84 | * not the one less. */ | |
85 | #define PTIMER_POLICY_NO_COUNTER_ROUND_DOWN (1 << 4) | |
86 | ||
086ede32 PM |
87 | /* |
88 | * Starting to run with a zero counter, or setting the counter to "0" via | |
89 | * ptimer_set_count() or ptimer_set_limit() will not trigger the timer | |
90 | * (though it will cause a reload). Only a counter decrement to "0" | |
91 | * will cause a trigger. Not compatible with NO_IMMEDIATE_TRIGGER; | |
af2a580f | 92 | * ptimer_init() will assert() that you don't set both. |
086ede32 PM |
93 | */ |
94 | #define PTIMER_POLICY_TRIGGER_ONLY_ON_DECREMENT (1 << 5) | |
95 | ||
49d4d9b6 PB |
96 | /* ptimer.c */ |
97 | typedef struct ptimer_state ptimer_state; | |
98 | typedef void (*ptimer_cb)(void *opaque); | |
99 | ||
78b6eaa6 PM |
100 | /** |
101 | * ptimer_init - Allocate and return a new ptimer | |
102 | * @callback: function to call on ptimer expiry | |
103 | * @callback_opaque: opaque pointer passed to @callback | |
104 | * @policy: PTIMER_POLICY_* bits specifying behaviour | |
105 | * | |
106 | * The ptimer returned must be freed using ptimer_free(). | |
107 | * | |
108 | * If a ptimer is created using this API then will use the | |
109 | * transaction-based API for modifying ptimer state: all calls | |
110 | * to functions which modify ptimer state: | |
111 | * - ptimer_set_period() | |
112 | * - ptimer_set_freq() | |
113 | * - ptimer_set_limit() | |
114 | * - ptimer_set_count() | |
115 | * - ptimer_run() | |
116 | * - ptimer_stop() | |
117 | * must be between matched calls to ptimer_transaction_begin() | |
118 | * and ptimer_transaction_commit(). When ptimer_transaction_commit() | |
119 | * is called it will evaluate the state of the timer after all the | |
120 | * changes in the transaction, and call the callback if necessary. | |
121 | * | |
122 | * The callback function is always called from within a transaction | |
123 | * begin/commit block, so the callback should not call the | |
124 | * ptimer_transaction_begin() function itself. If the callback changes | |
125 | * the ptimer state such that another ptimer expiry is triggered, then | |
126 | * the callback will be called a second time after the first call returns. | |
127 | */ | |
128 | ptimer_state *ptimer_init(ptimer_cb callback, | |
129 | void *callback_opaque, | |
130 | uint8_t policy_mask); | |
131 | ||
a7a305ae PM |
132 | /** |
133 | * ptimer_free - Free a ptimer | |
134 | * @s: timer to free | |
135 | * | |
af2a580f | 136 | * Free a ptimer created using ptimer_init(). |
a7a305ae | 137 | */ |
072bdb07 | 138 | void ptimer_free(ptimer_state *s); |
a7a305ae | 139 | |
78b6eaa6 PM |
140 | /** |
141 | * ptimer_transaction_begin() - Start a ptimer modification transaction | |
142 | * | |
143 | * This function must be called before making any calls to functions | |
144 | * which modify the ptimer's state (see the ptimer_init() documentation | |
145 | * for a list of these), and must always have a matched call to | |
146 | * ptimer_transaction_commit(). | |
147 | * It is an error to call this function for a BH-based ptimer; | |
148 | * attempting to do this will trigger an assert. | |
149 | */ | |
150 | void ptimer_transaction_begin(ptimer_state *s); | |
151 | ||
152 | /** | |
153 | * ptimer_transaction_commit() - Commit a ptimer modification transaction | |
154 | * | |
155 | * This function must be called after calls to functions which modify | |
156 | * the ptimer's state, and completes the update of the ptimer. If the | |
157 | * ptimer state now means that we should trigger the timer expiry | |
158 | * callback, it will be called directly. | |
159 | */ | |
160 | void ptimer_transaction_commit(ptimer_state *s); | |
161 | ||
a7a305ae PM |
162 | /** |
163 | * ptimer_set_period - Set counter increment interval in nanoseconds | |
164 | * @s: ptimer to configure | |
165 | * @period: period of the counter in nanoseconds | |
166 | * | |
167 | * Note that if your counter behaviour is specified as having a | |
168 | * particular frequency rather than a period then ptimer_set_freq() | |
169 | * may be more appropriate. | |
78b6eaa6 PM |
170 | * |
171 | * This function will assert if it is called outside a | |
af2a580f | 172 | * ptimer_transaction_begin/commit block. |
a7a305ae | 173 | */ |
49d4d9b6 | 174 | void ptimer_set_period(ptimer_state *s, int64_t period); |
a7a305ae | 175 | |
ad140dad PM |
176 | /** |
177 | * ptimer_set_period_from_clock - Set counter increment from a Clock | |
178 | * @s: ptimer to configure | |
179 | * @clk: pointer to Clock object to take period from | |
180 | * @divisor: value to scale the clock frequency down by | |
181 | * | |
182 | * If the ptimer is being driven from a Clock, this is the preferred | |
183 | * way to tell the ptimer about the period, because it avoids any | |
184 | * possible rounding errors that might happen if the internal | |
185 | * representation of the Clock period was converted to either a period | |
186 | * in ns or a frequency in Hz. | |
187 | * | |
188 | * If the ptimer should run at the same frequency as the clock, | |
189 | * pass 1 as the @divisor; if the ptimer should run at half the | |
190 | * frequency, pass 2, and so on. | |
191 | * | |
192 | * This function will assert if it is called outside a | |
193 | * ptimer_transaction_begin/commit block. | |
194 | */ | |
195 | void ptimer_set_period_from_clock(ptimer_state *s, const Clock *clock, | |
196 | unsigned int divisor); | |
197 | ||
a7a305ae PM |
198 | /** |
199 | * ptimer_set_freq - Set counter frequency in Hz | |
200 | * @s: ptimer to configure | |
201 | * @freq: counter frequency in Hz | |
202 | * | |
203 | * This does the same thing as ptimer_set_period(), so you only | |
204 | * need to call one of them. If the counter behaviour is specified | |
205 | * as setting the frequency then this function is more appropriate, | |
206 | * because it allows specifying an effective period which is | |
207 | * precise to fractions of a nanosecond, avoiding rounding errors. | |
78b6eaa6 PM |
208 | * |
209 | * This function will assert if it is called outside a | |
af2a580f | 210 | * ptimer_transaction_begin/commit block. |
a7a305ae | 211 | */ |
49d4d9b6 | 212 | void ptimer_set_freq(ptimer_state *s, uint32_t freq); |
a7a305ae PM |
213 | |
214 | /** | |
215 | * ptimer_get_limit - Get the configured limit of the ptimer | |
216 | * @s: ptimer to query | |
217 | * | |
218 | * This function returns the current limit (reload) value | |
219 | * of the down-counter; that is, the value which it will be | |
220 | * reset to when it hits zero. | |
221 | * | |
222 | * Generally timer devices using ptimers should be able to keep | |
223 | * their reload register state inside the ptimer using the get | |
224 | * and set limit functions rather than needing to also track it | |
225 | * in their own state structure. | |
226 | */ | |
578c4b2f | 227 | uint64_t ptimer_get_limit(ptimer_state *s); |
a7a305ae PM |
228 | |
229 | /** | |
230 | * ptimer_set_limit - Set the limit of the ptimer | |
231 | * @s: ptimer | |
232 | * @limit: initial countdown value | |
233 | * @reload: if nonzero, then reset the counter to the new limit | |
234 | * | |
235 | * Set the limit value of the down-counter. The @reload flag can | |
236 | * be used to emulate the behaviour of timers which immediately | |
237 | * reload the counter when their reload register is written to. | |
78b6eaa6 PM |
238 | * |
239 | * This function will assert if it is called outside a | |
af2a580f | 240 | * ptimer_transaction_begin/commit block. |
a7a305ae | 241 | */ |
49d4d9b6 | 242 | void ptimer_set_limit(ptimer_state *s, uint64_t limit, int reload); |
a7a305ae PM |
243 | |
244 | /** | |
245 | * ptimer_get_count - Get the current value of the ptimer | |
246 | * @s: ptimer | |
247 | * | |
248 | * Return the current value of the down-counter. This will | |
249 | * return the correct value whether the counter is enabled or | |
250 | * disabled. | |
251 | */ | |
49d4d9b6 | 252 | uint64_t ptimer_get_count(ptimer_state *s); |
a7a305ae PM |
253 | |
254 | /** | |
255 | * ptimer_set_count - Set the current value of the ptimer | |
256 | * @s: ptimer | |
257 | * @count: count value to set | |
258 | * | |
259 | * Set the value of the down-counter. If the counter is currently | |
260 | * enabled this will arrange for a timer callback at the appropriate | |
261 | * point in the future. | |
78b6eaa6 PM |
262 | * |
263 | * This function will assert if it is called outside a | |
af2a580f | 264 | * ptimer_transaction_begin/commit block. |
a7a305ae | 265 | */ |
49d4d9b6 | 266 | void ptimer_set_count(ptimer_state *s, uint64_t count); |
a7a305ae PM |
267 | |
268 | /** | |
269 | * ptimer_run - Start a ptimer counting | |
270 | * @s: ptimer | |
271 | * @oneshot: non-zero if this timer should only count down once | |
272 | * | |
af2a580f PM |
273 | * Start a ptimer counting down; when it reaches zero the callback function |
274 | * passed to ptimer_init() will be invoked. | |
b0142262 | 275 | * If the @oneshot argument is zero, |
a7a305ae PM |
276 | * the counter value will then be reloaded from the limit and it will |
277 | * start counting down again. If @oneshot is non-zero, then the counter | |
278 | * will disable itself when it reaches zero. | |
78b6eaa6 PM |
279 | * |
280 | * This function will assert if it is called outside a | |
af2a580f | 281 | * ptimer_transaction_begin/commit block. |
a7a305ae | 282 | */ |
49d4d9b6 | 283 | void ptimer_run(ptimer_state *s, int oneshot); |
a7a305ae PM |
284 | |
285 | /** | |
286 | * ptimer_stop - Stop a ptimer counting | |
287 | * @s: ptimer | |
288 | * | |
289 | * Pause a timer (the count stays at its current value until ptimer_run() | |
290 | * is called to start it counting again). | |
291 | * | |
292 | * Note that this can cause it to "lose" time, even if it is immediately | |
293 | * restarted. | |
78b6eaa6 PM |
294 | * |
295 | * This function will assert if it is called outside a | |
af2a580f | 296 | * ptimer_transaction_begin/commit block. |
a7a305ae | 297 | */ |
49d4d9b6 PB |
298 | void ptimer_stop(ptimer_state *s); |
299 | ||
701a8f76 PB |
300 | extern const VMStateDescription vmstate_ptimer; |
301 | ||
20bcf73f PM |
302 | #define VMSTATE_PTIMER(_field, _state) \ |
303 | VMSTATE_STRUCT_POINTER_V(_field, _state, 1, vmstate_ptimer, ptimer_state) | |
701a8f76 | 304 | |
a1f05e79 PM |
305 | #define VMSTATE_PTIMER_ARRAY(_f, _s, _n) \ |
306 | VMSTATE_ARRAY_OF_POINTER_TO_STRUCT(_f, _s, _n, 0, \ | |
307 | vmstate_ptimer, ptimer_state) | |
308 | ||
49d4d9b6 | 309 | #endif |