Add periodic timer implementation.

git-svn-id: svn://svn.savannah.nongnu.org/qemu/trunk@2846 c046a42c-6fe2-441c-8c8c-71466251a162

1 files changed, 164 insertions, 0 deletions

diff --git a/hw/ptimer.c b/hw/ptimer.c
new file mode 100644
index 0000000000..2f350fc09d
--- /dev/null
+++ b/hw/ptimer.c
@@ -0,0 +1,164 @@
+/* 
+ * General purpose implementation of a simple periodic countdown timer.
+ *
+ * Copyright (c) 2007 CodeSourcery.
+ *
+ * This code is licenced under the GNU LGPL.
+ */
+#include "vl.h"
+
+
+struct ptimer_state
+{
+    int enabled; /* 0 = disabled, 1 = periodic, 2 = oneshot.  */
+    uint32_t limit;
+    uint32_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;
+    }
+    qemu_mod_timer(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);
+    }
+}
+
+uint32_t ptimer_get_count(ptimer_state *s)
+{
+    int64_t now;
+    uint32_t counter;
+
+    if (s->enabled) {
+        now = qemu_get_clock(vm_clock);
+        /* 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 {
+            int64_t rem;
+            int64_t div;
+
+            rem = s->next_event - now;
+            div = s->period;
+            counter = rem / div;
+        }
+    } else {
+        counter = s->delta;
+    }
+    return counter;
+}
+
+void ptimer_set_count(ptimer_state *s, uint32_t count)
+{
+    s->delta = count;
+    if (s->enabled) {
+        s->next_event = qemu_get_clock(vm_clock);
+        ptimer_reload(s);
+    }
+}
+
+void ptimer_run(ptimer_state *s, int oneshot)
+{
+    if (s->period == 0) {
+        fprintf(stderr, "Timer with period zero, disabling\n");
+        return;
+    }
+    s->enabled = oneshot ? 2 : 1;
+    s->next_event = qemu_get_clock(vm_clock);
+    ptimer_reload(s);
+}
+
+/* Pause a timer.  Note that this may cause it to "loose" time, even if it
+   is immediately restarted.  */
+void ptimer_stop(ptimer_state *s)
+{
+    if (!s->enabled)
+        return;
+
+    s->delta = ptimer_get_count(s);
+    qemu_del_timer(s->timer);
+    s->enabled = 0;
+}
+
+/* Set counter increment interval in nanoseconds.  */
+void ptimer_set_period(ptimer_state *s, int64_t period)
+{
+    if (s->enabled) {
+        fprintf(stderr, "FIXME: ptimer_set_period with running timer");
+    }
+    s->period = period;
+    s->period_frac = 0;
+}
+
+/* Set counter frequency in Hz.  */
+void ptimer_set_freq(ptimer_state *s, uint32_t freq)
+{
+    if (s->enabled) {
+        fprintf(stderr, "FIXME: ptimer_set_freq with running timer");
+    }
+    s->period = 1000000000ll / freq;
+    s->period_frac = (1000000000ll << 32) / freq;
+}
+
+/* Set the initial countdown value.  If reload is nonzero then also set
+   count = limit.  */
+void ptimer_set_limit(ptimer_state *s, uint32_t limit, int reload)
+{
+    if (s->enabled) {
+        fprintf(stderr, "FIXME: ptimer_set_limit with running timer");
+    }
+    s->limit = limit;
+    if (reload)
+        s->delta = limit;
+}
+
+ptimer_state *ptimer_init(QEMUBH *bh)
+{
+    ptimer_state *s;
+
+    s = (ptimer_state *)qemu_mallocz(sizeof(ptimer_state));
+    s->bh = bh;
+    s->timer = qemu_new_timer(vm_clock, ptimer_tick, s);
+    return s;
+}
+