power: Add voltage domains to the clock domains

This patch adds the notion of voltage domains, and groups clock
domains that operate under the same voltage (i.e. power supply) into
domains. Each clock domain is required to be associated with a voltage
domain, and the latter requires the voltage to be explicitly set.

A voltage domain is an independently controllable voltage supply being
provided to section of the design. Thus, if you wish to perform
dynamic voltage scaling on a CPU, its clock domain should be
associated with a separate voltage domain.

The current implementation of the voltage domain does not take into
consideration cases where there are derived voltage domains running at
ratio of native voltage domains, as with the case where there can be
on-chip buck/boost (charge pumps) voltage regulation logic.

The regression and configuration scripts are updated with a generic
voltage domain for the system, and one for the CPUs.

src/python/m5/params.py

@@ -1250,6 +1250,23 @@ class Clock(ParamValue):
     def ini_str(self):
         return self.period.ini_str()
 
+class Voltage(float,ParamValue):
+    cxx_type = 'double'
+    def __new__(cls, value):
+        # convert to voltage
+        val = convert.toVoltage(value)
+        return super(cls, Voltage).__new__(cls, val)
+
+    def __str__(self):
+        return str(self.val)
+
+    def getValue(self):
+        value = float(self)
+        return value
+
+    def ini_str(self):
+        return '%f' % self.getValue()
+
 class NetworkBandwidth(float,ParamValue):
     cxx_type = 'float'
     def __new__(cls, value):
@@ -1637,7 +1654,7 @@ __all__ = ['Param', 'VectorParam',
            'TcpPort', 'UdpPort', 'EthernetAddr',
            'IpAddress', 'IpNetmask', 'IpWithPort',
            'MemorySize', 'MemorySize32',
-           'Latency', 'Frequency', 'Clock',
+           'Latency', 'Frequency', 'Clock', 'Voltage',
            'NetworkBandwidth', 'MemoryBandwidth',
            'AddrRange',
            'MaxAddr', 'MaxTick', 'AllMemory',

src/python/m5/util/convert.py

@@ -299,3 +299,15 @@ def toIpWithPort(value):
     if not 0 <= int(port) <= 0xffff:
         raise ValueError, 'invalid port %s' % port
     return (ip, int(port))
+
+def toVoltage(value):
+    if not isinstance(value, str):
+        raise TypeError, "wrong type '%s' should be str" % type(value)
+
+    if value.endswith('mV'):
+        return float(value[:-2]) * milli
+    elif value.endswith('V'):
+        return float(value[:-1])
+
+    raise ValueError, "cannot convert '%s' to voltage" % value
+