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_with_bh() will assert() that you don't set both. 76 */ 77 #define PTIMER_POLICY_TRIGGER_ONLY_ON_DECREMENT (1 << 5) 78 79 /* ptimer.c */ 80 typedef struct ptimer_state ptimer_state; 81 typedef void (*ptimer_cb)(void *opaque); 82 83 /** 84 * ptimer_init_with_bh - 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 */ 92 ptimer_state *ptimer_init_with_bh(QEMUBH *bh, uint8_t policy_mask); 93 94 /** 95 * ptimer_init - Allocate and return a new ptimer 96 * @callback: function to call on ptimer expiry 97 * @callback_opaque: opaque pointer passed to @callback 98 * @policy: PTIMER_POLICY_* bits specifying behaviour 99 * 100 * The ptimer returned must be freed using ptimer_free(). 101 * 102 * If a ptimer is created using this API then will use the 103 * transaction-based API for modifying ptimer state: all calls 104 * to functions which modify ptimer state: 105 * - ptimer_set_period() 106 * - ptimer_set_freq() 107 * - ptimer_set_limit() 108 * - ptimer_set_count() 109 * - ptimer_run() 110 * - ptimer_stop() 111 * must be between matched calls to ptimer_transaction_begin() 112 * and ptimer_transaction_commit(). When ptimer_transaction_commit() 113 * is called it will evaluate the state of the timer after all the 114 * changes in the transaction, and call the callback if necessary. 115 * 116 * The callback function is always called from within a transaction 117 * begin/commit block, so the callback should not call the 118 * ptimer_transaction_begin() function itself. If the callback changes 119 * the ptimer state such that another ptimer expiry is triggered, then 120 * the callback will be called a second time after the first call returns. 121 */ 122 ptimer_state *ptimer_init(ptimer_cb callback, 123 void *callback_opaque, 124 uint8_t policy_mask); 125 126 /** 127 * ptimer_free - Free a ptimer 128 * @s: timer to free 129 * 130 * Free a ptimer created using ptimer_init_with_bh() (including 131 * deleting the bottom half which it is using). 132 */ 133 void ptimer_free(ptimer_state *s); 134 135 /** 136 * ptimer_transaction_begin() - Start a ptimer modification transaction 137 * 138 * This function must be called before making any calls to functions 139 * which modify the ptimer's state (see the ptimer_init() documentation 140 * for a list of these), and must always have a matched call to 141 * ptimer_transaction_commit(). 142 * It is an error to call this function for a BH-based ptimer; 143 * attempting to do this will trigger an assert. 144 */ 145 void ptimer_transaction_begin(ptimer_state *s); 146 147 /** 148 * ptimer_transaction_commit() - Commit a ptimer modification transaction 149 * 150 * This function must be called after calls to functions which modify 151 * the ptimer's state, and completes the update of the ptimer. If the 152 * ptimer state now means that we should trigger the timer expiry 153 * callback, it will be called directly. 154 */ 155 void ptimer_transaction_commit(ptimer_state *s); 156 157 /** 158 * ptimer_set_period - Set counter increment interval in nanoseconds 159 * @s: ptimer to configure 160 * @period: period of the counter in nanoseconds 161 * 162 * Note that if your counter behaviour is specified as having a 163 * particular frequency rather than a period then ptimer_set_freq() 164 * may be more appropriate. 165 * 166 * This function will assert if it is called outside a 167 * ptimer_transaction_begin/commit block, unless this is a bottom-half ptimer. 168 */ 169 void ptimer_set_period(ptimer_state *s, int64_t period); 170 171 /** 172 * ptimer_set_freq - Set counter frequency in Hz 173 * @s: ptimer to configure 174 * @freq: counter frequency in Hz 175 * 176 * This does the same thing as ptimer_set_period(), so you only 177 * need to call one of them. If the counter behaviour is specified 178 * as setting the frequency then this function is more appropriate, 179 * because it allows specifying an effective period which is 180 * precise to fractions of a nanosecond, avoiding rounding errors. 181 * 182 * This function will assert if it is called outside a 183 * ptimer_transaction_begin/commit block, unless this is a bottom-half ptimer. 184 */ 185 void ptimer_set_freq(ptimer_state *s, uint32_t freq); 186 187 /** 188 * ptimer_get_limit - Get the configured limit of the ptimer 189 * @s: ptimer to query 190 * 191 * This function returns the current limit (reload) value 192 * of the down-counter; that is, the value which it will be 193 * reset to when it hits zero. 194 * 195 * Generally timer devices using ptimers should be able to keep 196 * their reload register state inside the ptimer using the get 197 * and set limit functions rather than needing to also track it 198 * in their own state structure. 199 */ 200 uint64_t ptimer_get_limit(ptimer_state *s); 201 202 /** 203 * ptimer_set_limit - Set the limit of the ptimer 204 * @s: ptimer 205 * @limit: initial countdown value 206 * @reload: if nonzero, then reset the counter to the new limit 207 * 208 * Set the limit value of the down-counter. The @reload flag can 209 * be used to emulate the behaviour of timers which immediately 210 * reload the counter when their reload register is written to. 211 * 212 * This function will assert if it is called outside a 213 * ptimer_transaction_begin/commit block, unless this is a bottom-half ptimer. 214 */ 215 void ptimer_set_limit(ptimer_state *s, uint64_t limit, int reload); 216 217 /** 218 * ptimer_get_count - Get the current value of the ptimer 219 * @s: ptimer 220 * 221 * Return the current value of the down-counter. This will 222 * return the correct value whether the counter is enabled or 223 * disabled. 224 */ 225 uint64_t ptimer_get_count(ptimer_state *s); 226 227 /** 228 * ptimer_set_count - Set the current value of the ptimer 229 * @s: ptimer 230 * @count: count value to set 231 * 232 * Set the value of the down-counter. If the counter is currently 233 * enabled this will arrange for a timer callback at the appropriate 234 * point in the future. 235 * 236 * This function will assert if it is called outside a 237 * ptimer_transaction_begin/commit block, unless this is a bottom-half ptimer. 238 */ 239 void ptimer_set_count(ptimer_state *s, uint64_t count); 240 241 /** 242 * ptimer_run - Start a ptimer counting 243 * @s: ptimer 244 * @oneshot: non-zero if this timer should only count down once 245 * 246 * Start a ptimer counting down; when it reaches zero the bottom half 247 * passed to ptimer_init_with_bh() will be invoked. 248 * If the @oneshot argument is zero, 249 * the counter value will then be reloaded from the limit and it will 250 * start counting down again. If @oneshot is non-zero, then the counter 251 * will disable itself when it reaches zero. 252 * 253 * This function will assert if it is called outside a 254 * ptimer_transaction_begin/commit block, unless this is a bottom-half ptimer. 255 */ 256 void ptimer_run(ptimer_state *s, int oneshot); 257 258 /** 259 * ptimer_stop - Stop a ptimer counting 260 * @s: ptimer 261 * 262 * Pause a timer (the count stays at its current value until ptimer_run() 263 * is called to start it counting again). 264 * 265 * Note that this can cause it to "lose" time, even if it is immediately 266 * restarted. 267 * 268 * This function will assert if it is called outside a 269 * ptimer_transaction_begin/commit block, unless this is a bottom-half ptimer. 270 */ 271 void ptimer_stop(ptimer_state *s); 272 273 extern const VMStateDescription vmstate_ptimer; 274 275 #define VMSTATE_PTIMER(_field, _state) \ 276 VMSTATE_STRUCT_POINTER_V(_field, _state, 1, vmstate_ptimer, ptimer_state) 277 278 #define VMSTATE_PTIMER_ARRAY(_f, _s, _n) \ 279 VMSTATE_ARRAY_OF_POINTER_TO_STRUCT(_f, _s, _n, 0, \ 280 vmstate_ptimer, ptimer_state) 281 282 #endif 283