power: Add basic DVFS support for gem5

Adds DVFS capabilities to gem5, by allowing users to specify lists for
frequencies and voltages in SrcClockDomains and VoltageDomains respectively.
A separate component, DVFSHandler, provides a small interface to change
operating points of the associated domains.

Clock domains will be linked to voltage domains and thus allow separate clock,
but shared voltage lines.

Currently all the valid performance-level updates are performed with a fixed
transition latency as specified for the domain.

Config file example:
...
vd = VoltageDomain(voltage = ['1V','0.95V','0.90V','0.85V'])
tsys.cluster1.clk_domain.clock = ['1GHz','700MHz','400MHz','230MHz']
tsys.cluster2.clk_domain.clock = ['1GHz','700MHz','400MHz','230MHz']
tsys.cluster1.clk_domain.domain_id = 0
tsys.cluster2.clk_domain.domain_id = 1
tsys.cluster1.clk_domain.voltage_domain = vd
tsys.cluster2.clk_domain.voltage_domain = vd
tsys.dvfs_handler.domains = [tsys.cluster1.clk_domain,
                             tsys.cluster2.clk_domain]
tsys.dvfs_handler.enable = True

1 files changed, 68 insertions, 0 deletions

diff --git a/src/sim/DVFSHandler.py b/src/sim/DVFSHandler.py
new file mode 100644
index 000000000..e6d558852
--- /dev/null
+++ b/src/sim/DVFSHandler.py
@@ -0,0 +1,68 @@
+# Copyright (c) 2013-2014 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
+
+from m5.params import *
+from m5.SimObject import SimObject
+from m5.proxy import *
+
+# The handler in its current form is design to be centeralized, one per system
+# and manages all the source clock domains (SrcClockDomain) it is configured to
+# handle.  The specific voltage and frequency points are configured per clock
+# and voltage domain.
+class DVFSHandler(SimObject):
+    type = 'DVFSHandler'
+    cxx_header = "sim/dvfs_handler.hh"
+
+    # List of controllable clock domains which in turn reference the appropriate
+    # voltage domains
+    domains = VectorParam.SrcClockDomain([], "list of domains")
+
+    # System domain (its clock and voltage) is not controllable
+    sys_clk_domain = Param.SrcClockDomain(Parent.clk_domain,
+                         "Clk domain in which the handler is instantiated")
+
+    enable = Param.Bool(False, "Enable/Disable the handler")
+
+    # The transition latency depends on how much time the PLLs and voltage
+    # regualators takes to migrate from current levels to the new level, is
+    # usally variable and hardware implementation dependent. In order to
+    # accomodate this effect with ease, we provide a fixed transition latency
+    # associated with all migrations. Configure this to maximum latency that
+    # the hardware will take to migratate between any two perforamnce levels.
+    transition_latency = Param.Latency('100us',
+                             "fixed latency for perf level migration")