Add periodic timer implementation.

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

hw/arm_timer.c

@@ -22,114 +22,24 @@
 #define TIMER_CTRL_ENABLE       (1 << 7)
 
 typedef struct {
-    int64_t next_time;
-    int64_t expires;
-    int64_t loaded;
-    QEMUTimer *timer;
+    ptimer_state *timer;
     uint32_t control;
-    uint32_t count;
     uint32_t limit;
-    int raw_freq;
     int freq;
     int int_level;
     qemu_irq irq;
 } arm_timer_state;
 
-/* Calculate the new expiry time of the given timer.  */
-
-static void arm_timer_reload(arm_timer_state *s)
-{
-    int64_t delay;
-
-    s->loaded = s->expires;
-    delay = muldiv64(s->count, ticks_per_sec, s->freq);
-    if (delay == 0)
-        delay = 1;
-    s->expires += delay;
-}
-
 /* Check all active timers, and schedule the next timer interrupt.  */
 
-static void arm_timer_update(arm_timer_state *s, int64_t now)
+static void arm_timer_update(arm_timer_state *s)
 {
-    int64_t next;
-
-    /* Ignore disabled timers.  */
-    if ((s->control & TIMER_CTRL_ENABLE) == 0)
-        return;
-    /* Ignore expired one-shot timers.  */
-    if (s->count == 0 && (s->control & TIMER_CTRL_ONESHOT))
-        return;
-    if (s->expires - now <= 0) {
-        /* Timer has expired.  */
-        s->int_level = 1;
-        if (s->control & TIMER_CTRL_ONESHOT) {
-            /* One-shot.  */
-            s->count = 0;
-        } else {
-            if ((s->control & TIMER_CTRL_PERIODIC) == 0) {
-                /* Free running.  */
-                if (s->control & TIMER_CTRL_32BIT)
-                    s->count = 0xffffffff;
-                else
-                    s->count = 0xffff;
-            } else {
-                  /* Periodic.  */
-                  s->count = s->limit;
-            }
-        }
-    }
-    while (s->expires - now <= 0) {
-        arm_timer_reload(s);
-    }
     /* Update interrupts.  */
     if (s->int_level && (s->control & TIMER_CTRL_IE)) {
         qemu_irq_raise(s->irq);
     } else {
         qemu_irq_lower(s->irq);
     }
-
-    next = now;
-    if (next - s->expires < 0)
-        next = s->expires;
-
-    /* Schedule the next timer interrupt.  */
-    if (next == now) {
-        qemu_del_timer(s->timer);
-        s->next_time = 0;
-    } else if (next != s->next_time) {
-        qemu_mod_timer(s->timer, next);
-        s->next_time = next;
-    }
-}
-
-/* Return the current value of the timer.  */
-static uint32_t arm_timer_getcount(arm_timer_state *s, int64_t now)
-{
-    int64_t left;
-    int64_t period;
-
-    if (s->count == 0)
-        return 0;
-    if ((s->control & TIMER_CTRL_ENABLE) == 0)
-        return s->count;
-    left = s->expires - now;
-    period = s->expires - s->loaded;
-    /* If the timer should have expired then return 0.  This can happen
-       when the host timer signal doesnt occur immediately.  It's better to
-       have a timer appear to sit at zero for a while than have it wrap
-       around before the guest interrupt is raised.  */
-    /* ??? Could we trigger the interrupt here?  */
-    if (left < 0)
-        return 0;
-    /* We need to calculate count * elapsed / period without overfowing.
-       Scale both elapsed and period so they fit in a 32-bit int.  */
-    while (period != (int32_t)period) {
-        period >>= 1;
-        left >>= 1;
-    }
-    return ((uint64_t)s->count * (uint64_t)(int32_t)left)
-            / (int32_t)period;
 }
 
 uint32_t arm_timer_read(void *opaque, target_phys_addr_t offset)
@@ -141,7 +51,7 @@ uint32_t arm_timer_read(void *opaque, target_phys_addr_t offset)
     case 6: /* TimerBGLoad */
         return s->limit;
     case 1: /* TimerValue */
-        return arm_timer_getcount(s, qemu_get_clock(vm_clock));
+        return ptimer_get_count(s->timer);
     case 2: /* TimerControl */
         return s->control;
     case 4: /* TimerRIS */
@@ -151,24 +61,40 @@ uint32_t arm_timer_read(void *opaque, target_phys_addr_t offset)
             return 0;
         return s->int_level;
     default:
-        cpu_abort (cpu_single_env, "arm_timer_read: Bad offset %x\n", offset);
+        cpu_abort (cpu_single_env, "arm_timer_read: Bad offset %x\n",
+                   (int)offset);
         return 0;
     }
 }
 
+/* Reset the timer limit after settings have changed.  */
+static void arm_timer_recalibrate(arm_timer_state *s, int reload)
+{
+    uint32_t limit;
+
+    if ((s->control & TIMER_CTRL_PERIODIC) == 0) {
+        /* Free running.  */
+        if (s->control & TIMER_CTRL_32BIT)
+            limit = 0xffffffff;
+        else
+            limit = 0xffff;
+    } else {
+          /* Periodic.  */
+          limit = s->limit;
+    }
+    ptimer_set_limit(s->timer, limit, reload);
+}
+
 static void arm_timer_write(void *opaque, target_phys_addr_t offset,
                             uint32_t value)
 {
     arm_timer_state *s = (arm_timer_state *)opaque;
-    int64_t now;
+    int freq;
 
-    now = qemu_get_clock(vm_clock);
     switch (offset >> 2) {
     case 0: /* TimerLoad */
         s->limit = value;
-        s->count = value;
-        s->expires = now;
-        arm_timer_reload(s);
+        arm_timer_recalibrate(s, 1);
         break;
     case 1: /* TimerValue */
         /* ??? Linux seems to want to write to this readonly register.
@@ -179,19 +105,20 @@ static void arm_timer_write(void *opaque, target_phys_addr_t offset,
             /* Pause the timer if it is running.  This may cause some
                inaccuracy dure to rounding, but avoids a whole lot of other
                messyness.  */
-            s->count = arm_timer_getcount(s, now);
+            ptimer_stop(s->timer);
         }
         s->control = value;
-        s->freq = s->raw_freq;
+        freq = s->freq;
         /* ??? Need to recalculate expiry time after changing divisor.  */
         switch ((value >> 2) & 3) {
-        case 1: s->freq >>= 4; break;
-        case 2: s->freq >>= 8; break;
+        case 1: freq >>= 4; break;
+        case 2: freq >>= 8; break;
         }
+        arm_timer_recalibrate(s, 0);
+        ptimer_set_freq(s->timer, freq);
         if (s->control & TIMER_CTRL_ENABLE) {
             /* Restart the timer if still enabled.  */
-            s->expires = now;
-            arm_timer_reload(s);
+            ptimer_run(s->timer, (s->control & TIMER_CTRL_ONESHOT) != 0);
         }
         break;
     case 3: /* TimerIntClr */
@@ -199,32 +126,34 @@ static void arm_timer_write(void *opaque, target_phys_addr_t offset,
         break;
     case 6: /* TimerBGLoad */
         s->limit = value;
+        arm_timer_recalibrate(s, 0);
         break;
     default:
-        cpu_abort (cpu_single_env, "arm_timer_write: Bad offset %x\n", offset);
+        cpu_abort (cpu_single_env, "arm_timer_write: Bad offset %x\n",
+                   (int)offset);
     }
-    arm_timer_update(s, now);
+    arm_timer_update(s);
 }
 
 static void arm_timer_tick(void *opaque)
 {
-    int64_t now;
-
-    now = qemu_get_clock(vm_clock);
-    arm_timer_update((arm_timer_state *)opaque, now);
+    arm_timer_state *s = (arm_timer_state *)opaque;
+    s->int_level = 1;
+    arm_timer_update(s);
 }
 
 static void *arm_timer_init(uint32_t freq, qemu_irq irq)
 {
     arm_timer_state *s;
+    QEMUBH *bh;
 
     s = (arm_timer_state *)qemu_mallocz(sizeof(arm_timer_state));
     s->irq = irq;
-    s->raw_freq = s->freq = 1000000;
+    s->freq = freq;
     s->control = TIMER_CTRL_IE;
-    s->count = 0xffffffff;
 
-    s->timer = qemu_new_timer(vm_clock, arm_timer_tick, s);
+    bh = qemu_bh_new(arm_timer_tick, s);
+    s->timer = ptimer_init(bh);
     /* ??? Save/restore.  */
     return s;
 }

hw/ptimer.c

+/* 
+ * 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;
+}
+

vl.c

@@ -6322,7 +6322,6 @@ void main_loop_wait(int timeout)
     }
 #endif
     qemu_aio_poll();
-    qemu_bh_poll();
 
     if (vm_running) {
         qemu_run_timers(&active_timers[QEMU_TIMER_VIRTUAL], 
@@ -6330,10 +6329,15 @@ void main_loop_wait(int timeout)
         /* run dma transfers, if any */
         DMA_run();
     }
-    
+
     /* real time timers */
     qemu_run_timers(&active_timers[QEMU_TIMER_REALTIME], 
                     qemu_get_clock(rt_clock));
+
+    /* Check bottom-halves last in case any of the earlier events triggered
+       them.  */
+    qemu_bh_poll();
+    
 }
 
 static CPUState *cur_cpu;