2 * General purpose implementation of a simple periodic countdown timer.
4 * Copyright (c) 2007 CodeSourcery.
6 * This code is licensed under the GNU LGPL.
8 #include "qemu/osdep.h"
10 #include "qemu/timer.h"
11 #include "hw/ptimer.h"
12 #include "qemu/host-utils.h"
13 #include "sysemu/replay.h"
17 uint8_t enabled; /* 0 = disabled, 1 = periodic, 2 = oneshot. */
28 /* Use a bottom-half routine to avoid reentrancy issues. */
29 static void ptimer_trigger(ptimer_state *s)
32 replay_bh_schedule_event(s->bh);
36 static void ptimer_reload(ptimer_state *s)
42 if (s->delta == 0 || s->period == 0) {
43 fprintf(stderr, "Timer with period zero, disabling\n");
48 s->last_event = s->next_event;
49 s->next_event = s->last_event + s->delta * s->period;
51 s->next_event += ((int64_t)s->period_frac * s->delta) >> 32;
53 timer_mod(s->timer, s->next_event);
56 static void ptimer_tick(void *opaque)
58 ptimer_state *s = (ptimer_state *)opaque;
61 if (s->enabled == 2) {
68 uint64_t ptimer_get_count(ptimer_state *s)
74 now = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL);
75 /* Figure out the current counter value. */
76 if (now - s->next_event > 0
78 /* Prevent timer underflowing if it should already have
87 /* We need to divide time by period, where time is stored in
88 rem (64-bit integer) and period is stored in period/period_frac
91 Doing full precision division is hard, so scale values and
92 do a 64-bit division. The result should be rounded down,
93 so that the rounding error never causes the timer to go
97 rem = s->next_event - now;
102 shift = clz1 < clz2 ? clz1 : clz2;
107 div |= ((uint64_t)s->period_frac << (shift - 32));
110 div |= (s->period_frac >> (32 - shift));
111 /* Look at remaining bits of period_frac and round div up if
113 if ((uint32_t)(s->period_frac << shift))
124 void ptimer_set_count(ptimer_state *s, uint64_t count)
128 s->next_event = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL);
133 void ptimer_run(ptimer_state *s, int oneshot)
138 if (s->period == 0) {
139 fprintf(stderr, "Timer with period zero, disabling\n");
142 s->enabled = oneshot ? 2 : 1;
143 s->next_event = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL);
147 /* Pause a timer. Note that this may cause it to "lose" time, even if it
148 is immediately restarted. */
149 void ptimer_stop(ptimer_state *s)
154 s->delta = ptimer_get_count(s);
159 /* Set counter increment interval in nanoseconds. */
160 void ptimer_set_period(ptimer_state *s, int64_t period)
165 s->next_event = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL);
170 /* Set counter frequency in Hz. */
171 void ptimer_set_freq(ptimer_state *s, uint32_t freq)
173 s->period = 1000000000ll / freq;
174 s->period_frac = (1000000000ll << 32) / freq;
176 s->next_event = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL);
181 /* Set the initial countdown value. If reload is nonzero then also set
183 void ptimer_set_limit(ptimer_state *s, uint64_t limit, int reload)
186 * Artificially limit timeout rate to something
187 * achievable under QEMU. Otherwise, QEMU spends all
188 * its time generating timer interrupts, and there
189 * is no forward progress.
190 * About ten microseconds is the fastest that really works
191 * on the current generation of host machines.
194 if (!use_icount && limit * s->period < 10000 && s->period) {
195 limit = 10000 / s->period;
201 if (s->enabled && reload) {
202 s->next_event = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL);
207 const VMStateDescription vmstate_ptimer = {
210 .minimum_version_id = 1,
211 .fields = (VMStateField[]) {
212 VMSTATE_UINT8(enabled, ptimer_state),
213 VMSTATE_UINT64(limit, ptimer_state),
214 VMSTATE_UINT64(delta, ptimer_state),
215 VMSTATE_UINT32(period_frac, ptimer_state),
216 VMSTATE_INT64(period, ptimer_state),
217 VMSTATE_INT64(last_event, ptimer_state),
218 VMSTATE_INT64(next_event, ptimer_state),
219 VMSTATE_TIMER_PTR(timer, ptimer_state),
220 VMSTATE_END_OF_LIST()
224 ptimer_state *ptimer_init(QEMUBH *bh)
228 s = (ptimer_state *)g_malloc0(sizeof(ptimer_state));
230 s->timer = timer_new_ns(QEMU_CLOCK_VIRTUAL, ptimer_tick, s);