diff --git a/external/devlib/devlib/module/cgroups.py b/external/devlib/devlib/module/cgroups.py
index 6cbab19e08900bd4ab4af4a5a988ca986ce3533c..b3cdb1d5d5ef6c90e74b2570eba8a43cc04edb72 100644
--- a/external/devlib/devlib/module/cgroups.py
+++ b/external/devlib/devlib/module/cgroups.py
@@ -411,7 +411,7 @@ class CgroupsModule(Module):
         for line in self.target.execute('{} cat /proc/cgroups'\
                 .format(self.target.busybox), as_root=self.target.is_rooted).splitlines()[1:]:
             line = line.strip()
-            if not line or line.startswith('#'):
+            if not line or line.startswith('#') or line.endswith('0'):
                 continue
             name, hierarchy, num_cgroups, enabled = line.split()
             subsystems.append(CgroupSubsystemEntry(name,
diff --git a/external/devlib/devlib/module/cpuidle.py b/external/devlib/devlib/module/cpuidle.py
index 93774bee016adafbc5ddd491c22a816fc4352e98..7b1704c73ac198911d8573b90e477c396b7b48a4 100644
--- a/external/devlib/devlib/module/cpuidle.py
+++ b/external/devlib/devlib/module/cpuidle.py
@@ -19,7 +19,9 @@ from operator import attrgetter
 from pprint import pformat
 
 from devlib.module import Module
+from devlib.exception import TargetStableError
 from devlib.utils.types import integer, boolean
+from devlib.utils.misc import memoized
 
 
 class CpuidleState(object):
@@ -170,8 +172,32 @@ class Cpuidle(Module):
     def get_driver(self):
         return self.target.read_value(self.target.path.join(self.root_path, 'current_driver'))
 
+    @memoized
+    def list_governors(self):
+        """Returns a list of supported idle governors."""
+        sysfile = self.target.path.join(self.root_path, 'available_governors')
+        output = self.target.read_value(sysfile)
+        return output.strip().split()
+
     def get_governor(self):
+        """Returns the currently selected idle governor."""
         path = self.target.path.join(self.root_path, 'current_governor_ro')
         if not self.target.file_exists(path):
             path = self.target.path.join(self.root_path, 'current_governor')
         return self.target.read_value(path)
+
+    def set_governor(self, governor):
+        """
+        Set the idle governor for the system.
+
+        :param governor: The name of the governor to be used. This must be
+        supported by the specific device.
+
+        :raises TargetStableError if governor is not supported by the CPU, or
+        if, for some reason, the governor could not be set.
+        """
+        supported = self.list_governors()
+        if governor not in supported:
+            raise TargetStableError('Governor {} not supported'.format(governor))
+        sysfile = self.target.path.join(self.root_path, 'current_governor')
+        self.target.write_value(sysfile, governor)
diff --git a/external/devlib/devlib/utils/android.py b/external/devlib/devlib/utils/android.py
index 32afa96b0bd2e877b7333c667bbe120235e95316..b46a825d8d9f389b4e0d514236b905d309553b77 100755
--- a/external/devlib/devlib/utils/android.py
+++ b/external/devlib/devlib/utils/android.py
@@ -385,9 +385,18 @@ class AdbConnection(ConnectionBase):
 
     def adb_root(self, enable=True):
         cmd = 'root' if enable else 'unroot'
-        output = adb_command(self.device, cmd, timeout=30, adb_server=self.adb_server)
-        if 'cannot run as root in production builds' in output:
-            raise TargetStableError(output)
+        try:
+            output = adb_command(self.device, cmd, timeout=30, adb_server=self.adb_server)
+        except subprocess.CalledProcessError as e:
+            # Ignore if we're already root
+            if 'adbd is already running as root' in e.output:
+                pass
+            else:
+                raise
+        else:
+            # Check separately as this does not cause a error exit code.
+            if 'cannot run as root in production builds' in output:
+                raise TargetStableError(output)
         AdbConnection._connected_as_root[self.device] = enable
 
     def wait_for_device(self, timeout=30):