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+/*
+ * Copyright (c) 2011 Advanced Micro Devices
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met: redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer;
+ * redistributions in binary form must reproduce the above copyright
+ * notice, this list of conditions and the following disclaimer in the
+ * documentation and/or other materials provided with the distribution;
+ * neither the name of the copyright holders nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ * Authors: Gabe Black
+ */
+
+/**
+ * @file This file defines the Root simobject and the methods used to control
+ * the time syncing mechanism provided through it.
+ *
+ * Time syncing prevents simulated time from passing faster than real time. It
+ * works by scheduling a periodic event that checks to see if its simulated
+ * period is shorter than its real period. If it is, it stalls the simulation
+ * until they're equal.
+ */
+
+#ifndef __SIM_ROOT_HH__
+#define __SIM_ROOT_HH__
+
+#include "base/time.hh"
+#include "params/Root.hh"
+#include "sim/eventq.hh"
+#include "sim/sim_object.hh"
+
+class Root : public SimObject
+{
+  private:
+    static Root *_root;
+
+  protected:
+    bool _enabled;
+    Time _period;
+    Tick _periodTick;
+    Time _spinThreshold;
+
+    Time lastTime;
+
+    void timeSync();
+    EventWrapper<Root, &Root::timeSync> syncEvent;
+    friend class EventWrapper<Root, &Root::timeSync>;
+
+  public:
+    /**
+     * Use this function to get a pointer to the single Root object in the
+     * simulation. This function asserts that such an object has actual been
+     * constructed to avoid having to perform that check everywhere the root
+     * is used. This is to allow calling the functions below.
+     *
+     * @return Pointer to the single root object.
+     */
+    static Root *
+    root()
+    {
+        assert(_root);
+        return _root;
+    }
+
+  public:
+
+    /// Check whether time syncing is enabled.
+    bool timeSyncEnabled() const { return _enabled; }
+    /// Retrieve the period for the sync event.
+    const Time timeSyncPeriod() const { return _period; }
+    /// Retrieve the threshold for time remaining to spin wait.
+    const Time timeSyncSpinThreshold() const { return _spinThreshold; }
+
+    /// Enable or disable time syncing.
+    void timeSyncEnable(bool en);
+    /// Configure the period for time sync events.
+    void timeSyncPeriod(Time newPeriod);
+    /// Set the threshold for time remaining to spin wait.
+    void timeSyncSpinThreshold(Time newThreshold);
+
+    Root(RootParams *p);
+};
+
+#endif // __SIM_ROOT_HH__