rt_config: Don't try to configure an offline cpu

As per [1], any attempt to configure a core's frequency will fail
if the first core of the associated frequency domain is offline.
Remove the assumption that the first cpu should be used when committing
the change to the device to resolve this.

[1] ARM-software#1217

wa/framework/target/runtime_config.py

@@ -306,13 +306,17 @@ def set_governor_tunables(obj, value, core):
 
     @staticmethod
     def set_param(obj, value, core, parameter):
-        '''Method to store passed parameter if it is not already specified for that cpu'''
-        cpus = resolve_unique_domain_cpus(core, obj.target)
-        for cpu in cpus:
-            if parameter in obj.config[cpu]:
-                msg = 'Cannot set "{}" for core "{}"; Parameter for CPU{} has already been set'
-                raise ConfigError(msg.format(parameter, core, cpu))
-            obj.config[cpu][parameter] = value
+        '''Method to store passed parameter if it is not already specified for that cpu frequency domain'''
+        resolved_cpus = resolve_unique_domain_cpus(core, obj.target)
+        for resovled  in resolved_cpus:
+            # Check no other cpus in the same domain have already been set.
+            cpus = obj.target.cpufreq.get_related_cpus(resovled)
+            for cpu in cpus:
+                if cpu in obj.config and parameter in obj.config[cpu]:
+                    msg = 'Cannot set "{}" for core "{}"; Parameter for CPU{} has already been set'
+                    raise ConfigError(msg.format(parameter, core, cpu))
+            # Once validated, store the ID of the first cpu resolved.
+            obj.config[resolved_cpus[0]][parameter] = value
 
     def __init__(self, target):
         self.config = defaultdict(dict)

wa/utils/misc.py

@@ -623,25 +623,27 @@ def resolve_cpus(name, target):
 def resolve_unique_domain_cpus(name, target):
     """
     Same as `resolve_cpus` above but only returns only the first cpu
-    in each of the different frequency domains. Requires cpufreq.
+    in each of the different frequency domains that are currently online.
+    Requires cpufreq.
     """
-    cpus = resolve_cpus(name, target)
+    cpus = set(resolve_cpus(name, target))
     if not target.has('cpufreq'):
         msg = 'Device does not appear to support cpufreq; ' \
               'Cannot obtain cpu domain information'
         raise TargetError(msg)
 
+    online_cpus = set(target.list_online_cpus())
     unique_cpus = []
     domain_cpus = []
-    for cpu in cpus:
+    for cpu in cpus.intersection(online_cpus):
         if cpu not in domain_cpus:
             try:
                 domain_cpus = target.cpufreq.get_related_cpus(cpu)
             except TargetStableError:
                 # Skip core if not online
                 continue
         if domain_cpus[0] not in unique_cpus:
-            unique_cpus.append(domain_cpus[0])
+            unique_cpus.append(cpu)
     return unique_cpus