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 /* ptimer.c */ 73 typedef struct ptimer_state ptimer_state; 74 typedef void (*ptimer_cb)(void *opaque); 75 76 /** 77 * ptimer_init - Allocate and return a new ptimer 78 * @bh: QEMU bottom half which is run on timer expiry 79 * @policy: PTIMER_POLICY_* bits specifying behaviour 80 * 81 * The ptimer returned must be freed using ptimer_free(). 82 * The ptimer takes ownership of @bh and will delete it 83 * when the ptimer is eventually freed. 84 */ 85 ptimer_state *ptimer_init(QEMUBH *bh, uint8_t policy_mask); 86 87 /** 88 * ptimer_free - Free a ptimer 89 * @s: timer to free 90 * 91 * Free a ptimer created using ptimer_init() (including 92 * deleting the bottom half which it is using). 93 */ 94 void ptimer_free(ptimer_state *s); 95 96 /** 97 * ptimer_set_period - Set counter increment interval in nanoseconds 98 * @s: ptimer to configure 99 * @period: period of the counter in nanoseconds 100 * 101 * Note that if your counter behaviour is specified as having a 102 * particular frequency rather than a period then ptimer_set_freq() 103 * may be more appropriate. 104 */ 105 void ptimer_set_period(ptimer_state *s, int64_t period); 106 107 /** 108 * ptimer_set_freq - Set counter frequency in Hz 109 * @s: ptimer to configure 110 * @freq: counter frequency in Hz 111 * 112 * This does the same thing as ptimer_set_period(), so you only 113 * need to call one of them. If the counter behaviour is specified 114 * as setting the frequency then this function is more appropriate, 115 * because it allows specifying an effective period which is 116 * precise to fractions of a nanosecond, avoiding rounding errors. 117 */ 118 void ptimer_set_freq(ptimer_state *s, uint32_t freq); 119 120 /** 121 * ptimer_get_limit - Get the configured limit of the ptimer 122 * @s: ptimer to query 123 * 124 * This function returns the current limit (reload) value 125 * of the down-counter; that is, the value which it will be 126 * reset to when it hits zero. 127 * 128 * Generally timer devices using ptimers should be able to keep 129 * their reload register state inside the ptimer using the get 130 * and set limit functions rather than needing to also track it 131 * in their own state structure. 132 */ 133 uint64_t ptimer_get_limit(ptimer_state *s); 134 135 /** 136 * ptimer_set_limit - Set the limit of the ptimer 137 * @s: ptimer 138 * @limit: initial countdown value 139 * @reload: if nonzero, then reset the counter to the new limit 140 * 141 * Set the limit value of the down-counter. The @reload flag can 142 * be used to emulate the behaviour of timers which immediately 143 * reload the counter when their reload register is written to. 144 */ 145 void ptimer_set_limit(ptimer_state *s, uint64_t limit, int reload); 146 147 /** 148 * ptimer_get_count - Get the current value of the ptimer 149 * @s: ptimer 150 * 151 * Return the current value of the down-counter. This will 152 * return the correct value whether the counter is enabled or 153 * disabled. 154 */ 155 uint64_t ptimer_get_count(ptimer_state *s); 156 157 /** 158 * ptimer_set_count - Set the current value of the ptimer 159 * @s: ptimer 160 * @count: count value to set 161 * 162 * Set the value of the down-counter. If the counter is currently 163 * enabled this will arrange for a timer callback at the appropriate 164 * point in the future. 165 */ 166 void ptimer_set_count(ptimer_state *s, uint64_t count); 167 168 /** 169 * ptimer_run - Start a ptimer counting 170 * @s: ptimer 171 * @oneshot: non-zero if this timer should only count down once 172 * 173 * Start a ptimer counting down; when it reaches zero the bottom half 174 * passed to ptimer_init() will be invoked. If the @oneshot argument is zero, 175 * the counter value will then be reloaded from the limit and it will 176 * start counting down again. If @oneshot is non-zero, then the counter 177 * will disable itself when it reaches zero. 178 */ 179 void ptimer_run(ptimer_state *s, int oneshot); 180 181 /** 182 * ptimer_stop - Stop a ptimer counting 183 * @s: ptimer 184 * 185 * Pause a timer (the count stays at its current value until ptimer_run() 186 * is called to start it counting again). 187 * 188 * Note that this can cause it to "lose" time, even if it is immediately 189 * restarted. 190 */ 191 void ptimer_stop(ptimer_state *s); 192 193 extern const VMStateDescription vmstate_ptimer; 194 195 #define VMSTATE_PTIMER(_field, _state) \ 196 VMSTATE_STRUCT_POINTER_V(_field, _state, 1, vmstate_ptimer, ptimer_state) 197 198 #define VMSTATE_PTIMER_ARRAY(_f, _s, _n) \ 199 VMSTATE_ARRAY_OF_POINTER_TO_STRUCT(_f, _s, _n, 0, \ 200 vmstate_ptimer, ptimer_state) 201 202 #endif 203