--- /dev/null
+/*
+ * General purpose implementation of a simple periodic countdown timer.
+ *
+ * Copyright (c) 2007 CodeSourcery.
+ *
+ * This code is licensed under the GNU LGPL.
+ */
+#include "hw/hw.h"
+#include "qemu/timer.h"
+#include "hw/ptimer.h"
+#include "qemu/host-utils.h"
+
+struct ptimer_state
+{
+ uint8_t enabled; /* 0 = disabled, 1 = periodic, 2 = oneshot. */
+ uint64_t limit;
+ uint64_t delta;
+ uint32_t period_frac;
+ int64_t period;
+ int64_t last_event;
+ int64_t next_event;
+ QEMUBH *bh;
+ QEMUTimer *timer;
+};
+
+/* Use a bottom-half routine to avoid reentrancy issues. */
+static void ptimer_trigger(ptimer_state *s)
+{
+ if (s->bh) {
+ qemu_bh_schedule(s->bh);
+ }
+}
+
+static void ptimer_reload(ptimer_state *s)
+{
+ if (s->delta == 0) {
+ ptimer_trigger(s);
+ s->delta = s->limit;
+ }
+ if (s->delta == 0 || s->period == 0) {
+ fprintf(stderr, "Timer with period zero, disabling\n");
+ s->enabled = 0;
+ return;
+ }
+
+ s->last_event = s->next_event;
+ s->next_event = s->last_event + s->delta * s->period;
+ if (s->period_frac) {
+ s->next_event += ((int64_t)s->period_frac * s->delta) >> 32;
+ }
+ timer_mod(s->timer, s->next_event);
+}
+
+static void ptimer_tick(void *opaque)
+{
+ ptimer_state *s = (ptimer_state *)opaque;
+ ptimer_trigger(s);
+ s->delta = 0;
+ if (s->enabled == 2) {
+ s->enabled = 0;
+ } else {
+ ptimer_reload(s);
+ }
+}
+
+uint64_t ptimer_get_count(ptimer_state *s)
+{
+ int64_t now;
+ uint64_t counter;
+
+ if (s->enabled) {
+ now = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL);
+ /* Figure out the current counter value. */
+ if (now - s->next_event > 0
+ || s->period == 0) {
+ /* Prevent timer underflowing if it should already have
+ triggered. */
+ counter = 0;
+ } else {
+ uint64_t rem;
+ uint64_t div;
+ int clz1, clz2;
+ int shift;
+
+ /* We need to divide time by period, where time is stored in
+ rem (64-bit integer) and period is stored in period/period_frac
+ (64.32 fixed point).
+
+ Doing full precision division is hard, so scale values and
+ do a 64-bit division. The result should be rounded down,
+ so that the rounding error never causes the timer to go
+ backwards.
+ */
+
+ rem = s->next_event - now;
+ div = s->period;
+
+ clz1 = clz64(rem);
+ clz2 = clz64(div);
+ shift = clz1 < clz2 ? clz1 : clz2;
+
+ rem <<= shift;
+ div <<= shift;
+ if (shift >= 32) {
+ div |= ((uint64_t)s->period_frac << (shift - 32));
+ } else {
+ if (shift != 0)
+ div |= (s->period_frac >> (32 - shift));
+ /* Look at remaining bits of period_frac and round div up if
+ necessary. */
+ if ((uint32_t)(s->period_frac << shift))
+ div += 1;
+ }
+ counter = rem / div;
+ }
+ } else {
+ counter = s->delta;
+ }
+ return counter;
+}
+
+void ptimer_set_count(ptimer_state *s, uint64_t count)
+{
+ s->delta = count;
+ if (s->enabled) {
+ s->next_event = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL);
+ ptimer_reload(s);
+ }
+}
+
+void ptimer_run(ptimer_state *s, int oneshot)
+{
+ if (s->enabled) {
+ return;
+ }
+ if (s->period == 0) {
+ fprintf(stderr, "Timer with period zero, disabling\n");
+ return;
+ }
+ s->enabled = oneshot ? 2 : 1;
+ s->next_event = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL);
+ ptimer_reload(s);
+}
+
+/* Pause a timer. Note that this may cause it to "lose" time, even if it
+ is immediately restarted. */
+void ptimer_stop(ptimer_state *s)
+{
+ if (!s->enabled)
+ return;
+
+ s->delta = ptimer_get_count(s);
+ timer_del(s->timer);
+ s->enabled = 0;
+}
+
+/* Set counter increment interval in nanoseconds. */
+void ptimer_set_period(ptimer_state *s, int64_t period)
+{
+ s->period = period;
+ s->period_frac = 0;
+ if (s->enabled) {
+ s->next_event = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL);
+ ptimer_reload(s);
+ }
+}
+
+/* Set counter frequency in Hz. */
+void ptimer_set_freq(ptimer_state *s, uint32_t freq)
+{
+ s->period = 1000000000ll / freq;
+ s->period_frac = (1000000000ll << 32) / freq;
+ if (s->enabled) {
+ s->next_event = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL);
+ ptimer_reload(s);
+ }
+}
+
+/* Set the initial countdown value. If reload is nonzero then also set
+ count = limit. */
+void ptimer_set_limit(ptimer_state *s, uint64_t limit, int reload)
+{
+ /*
+ * Artificially limit timeout rate to something
+ * achievable under QEMU. Otherwise, QEMU spends all
+ * its time generating timer interrupts, and there
+ * is no forward progress.
+ * About ten microseconds is the fastest that really works
+ * on the current generation of host machines.
+ */
+
+ if (!use_icount && limit * s->period < 10000 && s->period) {
+ limit = 10000 / s->period;
+ }
+
+ s->limit = limit;
+ if (reload)
+ s->delta = limit;
+ if (s->enabled && reload) {
+ s->next_event = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL);
+ ptimer_reload(s);
+ }
+}
+
+const VMStateDescription vmstate_ptimer = {
+ .name = "ptimer",
+ .version_id = 1,
+ .minimum_version_id = 1,
+ .fields = (VMStateField[]) {
+ VMSTATE_UINT8(enabled, ptimer_state),
+ VMSTATE_UINT64(limit, ptimer_state),
+ VMSTATE_UINT64(delta, ptimer_state),
+ VMSTATE_UINT32(period_frac, ptimer_state),
+ VMSTATE_INT64(period, ptimer_state),
+ VMSTATE_INT64(last_event, ptimer_state),
+ VMSTATE_INT64(next_event, ptimer_state),
+ VMSTATE_TIMER_PTR(timer, ptimer_state),
+ VMSTATE_END_OF_LIST()
+ }
+};
+
+ptimer_state *ptimer_init(QEMUBH *bh)
+{
+ ptimer_state *s;
+
+ s = (ptimer_state *)g_malloc0(sizeof(ptimer_state));
+ s->bh = bh;
+ s->timer = timer_new_ns(QEMU_CLOCK_VIRTUAL, ptimer_tick, s);
+ return s;
+}
Code Review / kvmfornfv.git / blobdiff