sim: Add the notion of clock domains to all ClockedObjects

This patch adds the notion of source- and derived-clock domains to the
ClockedObjects. As such, all clock information is moved to the clock
domain, and the ClockedObjects are grouped into domains.

The clock domains are either source domains, with a specific clock
period, or derived domains that have a parent domain and a divider
(potentially chained). For piece of logic that runs at a derived clock
(a ratio of the clock its parent is running at) the necessary derived
clock domain is created from its corresponding parent clock
domain. For now, the derived clock domain only supports a divider,
thus ensuring a lower speed compared to its parent. Multiplier
functionality implies a PLL logic that has not been modelled yet
(create a separate clock instead).

The clock domains should be used as a mechanism to provide a
controllable clock source that affects clock for every clocked object
lying beneath it. The clock of the domain can (in a future patch) be
controlled by a handler responsible for dynamic frequency scaling of
the respective clock domains.

All the config scripts have been retro-fitted with clock domains. For
the System a default SrcClockDomain is created. For CPUs that run at a
different speed than the system, there is a seperate clock domain
created. This domain incorporates the CPU and the associated
caches. As before, Ruby runs under its own clock domain.

The clock period of all domains are pre-computed, such that no virtual
functions or multiplications are needed when calling
clockPeriod. Instead, the clock period is pre-computed when any
changes occur. For this to be possible, each clock domain tracks its
children.

1 files changed, 160 insertions, 0 deletions

diff --git a/src/sim/clock_domain.hh b/src/sim/clock_domain.hh
new file mode 100644
index 000000000..c3f53e675
--- /dev/null
+++ b/src/sim/clock_domain.hh
@@ -0,0 +1,160 @@
+/*
+ * Copyright (c) 2013 ARM Limited
+ * All rights reserved
+ *
+ * The license below extends only to copyright in the software and shall
+ * not be construed as granting a license to any other intellectual
+ * property including but not limited to intellectual property relating
+ * to a hardware implementation of the functionality of the software
+ * licensed hereunder.  You may use the software subject to the license
+ * terms below provided that you ensure that this notice is replicated
+ * unmodified and in its entirety in all distributions of the software,
+ * modified or unmodified, in source code or in binary form.
+ *
+ * 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: Vasileios Spiliopoulos
+ *          Akash Bagdia
+ */
+
+/**
+ * @file
+ * ClockDomain declarations.
+ */
+
+#ifndef __SIM_CLOCK_DOMAIN_HH__
+#define __SIM_CLOCK_DOMAIN_HH__
+
+#include "base/statistics.hh"
+#include "params/ClockDomain.hh"
+#include "params/DerivedClockDomain.hh"
+#include "params/SrcClockDomain.hh"
+#include "sim/sim_object.hh"
+
+/**
+ * Forward declaration
+ */
+class DerivedClockDomain;
+
+/**
+ * The ClockDomain provides clock to group of clocked objects bundled
+ * under the same clock domain. The clock domains provide support for
+ * a hierarchial structure with source and derived domains.
+ */
+class ClockDomain : public SimObject
+{
+
+  protected:
+
+    /**
+     * Pre-computed clock period in ticks. This is populated by the
+     * inheriting classes based on how their period is determined.
+     */
+    Tick _clockPeriod;
+
+    /**
+     * Pointers to potential derived clock domains so we can propagate
+     * changes.
+     */
+    std::vector<DerivedClockDomain*> children;
+
+  public:
+
+    typedef ClockDomainParams Params;
+    ClockDomain(const Params *p) : SimObject(p), _clockPeriod(0) {}
+
+    /**
+     * Get the clock period.
+     *
+     * @return Clock period in ticks
+     */
+    inline Tick clockPeriod() const { return _clockPeriod; }
+
+    /**
+     * Add a derived domain.
+     *
+     * @param Derived domain to add as a child
+     */
+    void addDerivedDomain(DerivedClockDomain *clock_domain)
+    { children.push_back(clock_domain); }
+
+};
+
+/**
+ * The source clock domains provides the notion of a clock domain that is
+ * connected to a tunable clock source. It maintains the clock period and
+ * provides methods for setting/getting the clock.
+ */
+class SrcClockDomain : public ClockDomain
+{
+
+  public:
+
+    typedef SrcClockDomainParams Params;
+    SrcClockDomain(const Params *p);
+
+    /**
+     * Set new clock value
+     * @param clock The new clock period in ticks
+     */
+    void clockPeriod(Tick clock_period);
+
+};
+
+/**
+ * The derived clock domains provides the notion of a clock domain
+ * that is connected to a parent clock domain that can either be a
+ * source clock domain or a derived clock domain. It maintains the
+ * clock divider and provides methods for getting the clock.
+ */
+class DerivedClockDomain: public ClockDomain
+{
+
+  public:
+
+    typedef DerivedClockDomainParams Params;
+    DerivedClockDomain(const Params *p);
+
+    /**
+     * Called by the parent clock domain to propagate changes. This
+     * also involves propagating the change further to any children of
+     * the derived domain itself.
+     */
+    void updateClockPeriod();
+
+  private:
+
+    /**
+     * Reference to the parent clock domain this clock domain derives
+     * its clock period from
+     */
+    ClockDomain &parent;
+
+    /**
+     * Local clock divider of the domain
+     */
+    const uint64_t clockDivider;
+};
+
+#endif