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 280