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 | |