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 */ 80 typedef struct ptimer_state ptimer_state; 81 typedef 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 */ 92 ptimer_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 */ 101 void 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 */ 112 void 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 */ 125 void 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 */ 140 uint64_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 */ 152 void 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 */ 162 uint64_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 */ 173 void 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 */ 186 void 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 */ 198 void ptimer_stop(ptimer_state *s); 199 200 extern 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