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 #include "migration/vmstate.h" 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 QEMU bottom half handler, 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 * Forgetting to set the period/frequency (or setting it to zero) is a 24 * bug in the QEMU device and will cause warning messages to be printed 25 * to stderr when the guest attempts to enable the timer. 26 */ 27 28 /* The default ptimer policy retains backward compatibility with the legacy 29 * timers. Custom policies are adjusting the default one. Consider providing 30 * a correct policy for your timer. 31 * 32 * The rough edges of the default policy: 33 * - Starting to run with a period = 0 emits error message and stops the 34 * timer without a trigger. 35 * 36 * - Setting period to 0 of the running timer emits error message and 37 * stops the timer without a trigger. 38 * 39 * - Starting to run with counter = 0 or setting it to "0" while timer 40 * is running causes a trigger and reloads counter with a limit value. 41 * If limit = 0, ptimer emits error message and stops the timer. 42 * 43 * - Counter value of the running timer is one less than the actual value. 44 * 45 * - Changing period/frequency of the running timer loses time elapsed 46 * since the last period, effectively restarting the timer with a 47 * counter = counter value at the moment of change (.i.e. one less). 48 */ 49 #define PTIMER_POLICY_DEFAULT 0 50 51 /* Periodic timer counter stays with "0" for a one period before wrapping 52 * around. */ 53 #define PTIMER_POLICY_WRAP_AFTER_ONE_PERIOD (1 << 0) 54 55 /* Running periodic timer that has counter = limit = 0 would continuously 56 * re-trigger every period. */ 57 #define PTIMER_POLICY_CONTINUOUS_TRIGGER (1 << 1) 58 59 /* Starting to run with/setting counter to "0" won't trigger immediately, 60 * but after a one period for both oneshot and periodic modes. */ 61 #define PTIMER_POLICY_NO_IMMEDIATE_TRIGGER (1 << 2) 62 63 /* Starting to run with/setting counter to "0" won't re-load counter 64 * immediately, but after a one period. */ 65 #define PTIMER_POLICY_NO_IMMEDIATE_RELOAD (1 << 3) 66 67 /* Make counter value of the running timer represent the actual value and 68 * not the one less. */ 69 #define PTIMER_POLICY_NO_COUNTER_ROUND_DOWN (1 << 4) 70 71 /* 72 * Starting to run with a zero counter, or setting the counter to "0" via 73 * ptimer_set_count() or ptimer_set_limit() will not trigger the timer 74 * (though it will cause a reload). Only a counter decrement to "0" 75 * will cause a trigger. Not compatible with NO_IMMEDIATE_TRIGGER; 76 * ptimer_init() will assert() that you don't set both. 77 */ 78 #define PTIMER_POLICY_TRIGGER_ONLY_ON_DECREMENT (1 << 5) 79 80 /* ptimer.c */ 81 typedef struct ptimer_state ptimer_state; 82 typedef void (*ptimer_cb)(void *opaque); 83 84 /** 85 * ptimer_init - Allocate and return a new ptimer 86 * @bh: QEMU bottom half which is run on timer expiry 87 * @policy: PTIMER_POLICY_* bits specifying behaviour 88 * 89 * The ptimer returned must be freed using ptimer_free(). 90 * The ptimer takes ownership of @bh and will delete it 91 * when the ptimer is eventually freed. 92 */ 93 ptimer_state *ptimer_init(QEMUBH *bh, uint8_t policy_mask); 94 95 /** 96 * ptimer_free - Free a ptimer 97 * @s: timer to free 98 * 99 * Free a ptimer created using ptimer_init() (including 100 * deleting the bottom half which it is using). 101 */ 102 void ptimer_free(ptimer_state *s); 103 104 /** 105 * ptimer_set_period - Set counter increment interval in nanoseconds 106 * @s: ptimer to configure 107 * @period: period of the counter in nanoseconds 108 * 109 * Note that if your counter behaviour is specified as having a 110 * particular frequency rather than a period then ptimer_set_freq() 111 * may be more appropriate. 112 */ 113 void ptimer_set_period(ptimer_state *s, int64_t period); 114 115 /** 116 * ptimer_set_freq - Set counter frequency in Hz 117 * @s: ptimer to configure 118 * @freq: counter frequency in Hz 119 * 120 * This does the same thing as ptimer_set_period(), so you only 121 * need to call one of them. If the counter behaviour is specified 122 * as setting the frequency then this function is more appropriate, 123 * because it allows specifying an effective period which is 124 * precise to fractions of a nanosecond, avoiding rounding errors. 125 */ 126 void ptimer_set_freq(ptimer_state *s, uint32_t freq); 127 128 /** 129 * ptimer_get_limit - Get the configured limit of the ptimer 130 * @s: ptimer to query 131 * 132 * This function returns the current limit (reload) value 133 * of the down-counter; that is, the value which it will be 134 * reset to when it hits zero. 135 * 136 * Generally timer devices using ptimers should be able to keep 137 * their reload register state inside the ptimer using the get 138 * and set limit functions rather than needing to also track it 139 * in their own state structure. 140 */ 141 uint64_t ptimer_get_limit(ptimer_state *s); 142 143 /** 144 * ptimer_set_limit - Set the limit of the ptimer 145 * @s: ptimer 146 * @limit: initial countdown value 147 * @reload: if nonzero, then reset the counter to the new limit 148 * 149 * Set the limit value of the down-counter. The @reload flag can 150 * be used to emulate the behaviour of timers which immediately 151 * reload the counter when their reload register is written to. 152 */ 153 void ptimer_set_limit(ptimer_state *s, uint64_t limit, int reload); 154 155 /** 156 * ptimer_get_count - Get the current value of the ptimer 157 * @s: ptimer 158 * 159 * Return the current value of the down-counter. This will 160 * return the correct value whether the counter is enabled or 161 * disabled. 162 */ 163 uint64_t ptimer_get_count(ptimer_state *s); 164 165 /** 166 * ptimer_set_count - Set the current value of the ptimer 167 * @s: ptimer 168 * @count: count value to set 169 * 170 * Set the value of the down-counter. If the counter is currently 171 * enabled this will arrange for a timer callback at the appropriate 172 * point in the future. 173 */ 174 void ptimer_set_count(ptimer_state *s, uint64_t count); 175 176 /** 177 * ptimer_run - Start a ptimer counting 178 * @s: ptimer 179 * @oneshot: non-zero if this timer should only count down once 180 * 181 * Start a ptimer counting down; when it reaches zero the bottom half 182 * passed to ptimer_init() will be invoked. If the @oneshot argument is zero, 183 * the counter value will then be reloaded from the limit and it will 184 * start counting down again. If @oneshot is non-zero, then the counter 185 * will disable itself when it reaches zero. 186 */ 187 void ptimer_run(ptimer_state *s, int oneshot); 188 189 /** 190 * ptimer_stop - Stop a ptimer counting 191 * @s: ptimer 192 * 193 * Pause a timer (the count stays at its current value until ptimer_run() 194 * is called to start it counting again). 195 * 196 * Note that this can cause it to "lose" time, even if it is immediately 197 * restarted. 198 */ 199 void ptimer_stop(ptimer_state *s); 200 201 extern const VMStateDescription vmstate_ptimer; 202 203 #define VMSTATE_PTIMER(_field, _state) \ 204 VMSTATE_STRUCT_POINTER_V(_field, _state, 1, vmstate_ptimer, ptimer_state) 205 206 #define VMSTATE_PTIMER_ARRAY(_f, _s, _n) \ 207 VMSTATE_ARRAY_OF_POINTER_TO_STRUCT(_f, _s, _n, 0, \ 208 vmstate_ptimer, ptimer_state) 209 210 #endif 211