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-common.h" 12 #include "qemu/timer.h" 13 #include "migration/vmstate.h" 14 15 /* The ptimer API implements a simple periodic countdown timer. 16 * The countdown timer has a value (which can be read and written via 17 * ptimer_get_count() and ptimer_set_count()). When it is enabled 18 * using ptimer_run(), the value will count downwards at the frequency 19 * which has been configured using ptimer_set_period() or ptimer_set_freq(). 20 * When it reaches zero it will trigger a QEMU bottom half handler, and 21 * can be set to either reload itself from a specified limit value 22 * and keep counting down, or to stop (as a one-shot timer). 23 * 24 * Forgetting to set the period/frequency (or setting it to zero) is a 25 * bug in the QEMU device and will cause warning messages to be printed 26 * to stderr when the guest attempts to enable the timer. 27 */ 28 29 /* The default ptimer policy retains backward compatibility with the legacy 30 * timers. Custom policies are adjusting the default one. Consider providing 31 * a correct policy for your timer. 32 * 33 * The rough edges of the default policy: 34 * - Starting to run with a period = 0 emits error message and stops the 35 * timer without a trigger. 36 * 37 * - Setting period to 0 of the running timer emits error message and 38 * stops the timer without a trigger. 39 * 40 * - Starting to run with counter = 0 or setting it to "0" while timer 41 * is running causes a trigger and reloads counter with a limit value. 42 * If limit = 0, ptimer emits error message and stops the timer. 43 * 44 * - Counter value of the running timer is one less than the actual value. 45 * 46 * - Changing period/frequency of the running timer loses time elapsed 47 * since the last period, effectively restarting the timer with a 48 * counter = counter value at the moment of change (.i.e. one less). 49 */ 50 #define PTIMER_POLICY_DEFAULT 0 51 52 /* Periodic timer counter stays with "0" for a one period before wrapping 53 * around. */ 54 #define PTIMER_POLICY_WRAP_AFTER_ONE_PERIOD (1 << 0) 55 56 /* Running periodic timer that has counter = limit = 0 would continuously 57 * re-trigger every period. */ 58 #define PTIMER_POLICY_CONTINUOUS_TRIGGER (1 << 1) 59 60 /* Starting to run with/setting counter to "0" won't trigger immediately, 61 * but after a one period for both oneshot and periodic modes. */ 62 #define PTIMER_POLICY_NO_IMMEDIATE_TRIGGER (1 << 2) 63 64 /* Starting to run with/setting counter to "0" won't re-load counter 65 * immediately, but after a one period. */ 66 #define PTIMER_POLICY_NO_IMMEDIATE_RELOAD (1 << 3) 67 68 /* Make counter value of the running timer represent the actual value and 69 * not the one less. */ 70 #define PTIMER_POLICY_NO_COUNTER_ROUND_DOWN (1 << 4) 71 72 /* 73 * Starting to run with a zero counter, or setting the counter to "0" via 74 * ptimer_set_count() or ptimer_set_limit() will not trigger the timer 75 * (though it will cause a reload). Only a counter decrement to "0" 76 * will cause a trigger. Not compatible with NO_IMMEDIATE_TRIGGER; 77 * ptimer_init() will assert() that you don't set both. 78 */ 79 #define PTIMER_POLICY_TRIGGER_ONLY_ON_DECREMENT (1 << 5) 80 81 /* ptimer.c */ 82 typedef struct ptimer_state ptimer_state; 83 typedef void (*ptimer_cb)(void *opaque); 84 85 /** 86 * ptimer_init - Allocate and return a new ptimer 87 * @bh: QEMU bottom half which is run on timer expiry 88 * @policy: PTIMER_POLICY_* bits specifying behaviour 89 * 90 * The ptimer returned must be freed using ptimer_free(). 91 * The ptimer takes ownership of @bh and will delete it 92 * when the ptimer is eventually freed. 93 */ 94 ptimer_state *ptimer_init(QEMUBH *bh, uint8_t policy_mask); 95 96 /** 97 * ptimer_free - Free a ptimer 98 * @s: timer to free 99 * 100 * Free a ptimer created using ptimer_init() (including 101 * deleting the bottom half which it is using). 102 */ 103 void ptimer_free(ptimer_state *s); 104 105 /** 106 * ptimer_set_period - Set counter increment interval in nanoseconds 107 * @s: ptimer to configure 108 * @period: period of the counter in nanoseconds 109 * 110 * Note that if your counter behaviour is specified as having a 111 * particular frequency rather than a period then ptimer_set_freq() 112 * may be more appropriate. 113 */ 114 void ptimer_set_period(ptimer_state *s, int64_t period); 115 116 /** 117 * ptimer_set_freq - Set counter frequency in Hz 118 * @s: ptimer to configure 119 * @freq: counter frequency in Hz 120 * 121 * This does the same thing as ptimer_set_period(), so you only 122 * need to call one of them. If the counter behaviour is specified 123 * as setting the frequency then this function is more appropriate, 124 * because it allows specifying an effective period which is 125 * precise to fractions of a nanosecond, avoiding rounding errors. 126 */ 127 void ptimer_set_freq(ptimer_state *s, uint32_t freq); 128 129 /** 130 * ptimer_get_limit - Get the configured limit of the ptimer 131 * @s: ptimer to query 132 * 133 * This function returns the current limit (reload) value 134 * of the down-counter; that is, the value which it will be 135 * reset to when it hits zero. 136 * 137 * Generally timer devices using ptimers should be able to keep 138 * their reload register state inside the ptimer using the get 139 * and set limit functions rather than needing to also track it 140 * in their own state structure. 141 */ 142 uint64_t ptimer_get_limit(ptimer_state *s); 143 144 /** 145 * ptimer_set_limit - Set the limit of the ptimer 146 * @s: ptimer 147 * @limit: initial countdown value 148 * @reload: if nonzero, then reset the counter to the new limit 149 * 150 * Set the limit value of the down-counter. The @reload flag can 151 * be used to emulate the behaviour of timers which immediately 152 * reload the counter when their reload register is written to. 153 */ 154 void ptimer_set_limit(ptimer_state *s, uint64_t limit, int reload); 155 156 /** 157 * ptimer_get_count - Get the current value of the ptimer 158 * @s: ptimer 159 * 160 * Return the current value of the down-counter. This will 161 * return the correct value whether the counter is enabled or 162 * disabled. 163 */ 164 uint64_t ptimer_get_count(ptimer_state *s); 165 166 /** 167 * ptimer_set_count - Set the current value of the ptimer 168 * @s: ptimer 169 * @count: count value to set 170 * 171 * Set the value of the down-counter. If the counter is currently 172 * enabled this will arrange for a timer callback at the appropriate 173 * point in the future. 174 */ 175 void ptimer_set_count(ptimer_state *s, uint64_t count); 176 177 /** 178 * ptimer_run - Start a ptimer counting 179 * @s: ptimer 180 * @oneshot: non-zero if this timer should only count down once 181 * 182 * Start a ptimer counting down; when it reaches zero the bottom half 183 * passed to ptimer_init() will be invoked. If the @oneshot argument is zero, 184 * the counter value will then be reloaded from the limit and it will 185 * start counting down again. If @oneshot is non-zero, then the counter 186 * will disable itself when it reaches zero. 187 */ 188 void ptimer_run(ptimer_state *s, int oneshot); 189 190 /** 191 * ptimer_stop - Stop a ptimer counting 192 * @s: ptimer 193 * 194 * Pause a timer (the count stays at its current value until ptimer_run() 195 * is called to start it counting again). 196 * 197 * Note that this can cause it to "lose" time, even if it is immediately 198 * restarted. 199 */ 200 void ptimer_stop(ptimer_state *s); 201 202 extern const VMStateDescription vmstate_ptimer; 203 204 #define VMSTATE_PTIMER(_field, _state) \ 205 VMSTATE_STRUCT_POINTER_V(_field, _state, 1, vmstate_ptimer, ptimer_state) 206 207 #define VMSTATE_PTIMER_ARRAY(_f, _s, _n) \ 208 VMSTATE_ARRAY_OF_POINTER_TO_STRUCT(_f, _s, _n, 0, \ 209 vmstate_ptimer, ptimer_state) 210 211 #endif 212