Added frequency stats and c-state residency to CrOS power monitor.

tools/telemetry/telemetry/core/platform/power_monitor/cros_sysfs_platform.py

Index: tools/telemetry/telemetry/core/platform/power_monitor/cros_sysfs_platform.py
diff --git a/tools/telemetry/telemetry/core/platform/power_monitor/cros_sysfs_platform.py b/tools/telemetry/telemetry/core/platform/power_monitor/cros_sysfs_platform.py
new file mode 100644
index 0000000000000000000000000000000000000000..52573447be84a47cd2241c99696caa3fc059d99e
--- /dev/null
+++ b/tools/telemetry/telemetry/core/platform/power_monitor/cros_sysfs_platform.py
@@ -0,0 +1,47 @@
+# Copyright 2014 The Chromium Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+from telemetry.core.platform.power_monitor import sysfs_platform
+
+
+class CrosSysfsPlatform(sysfs_platform.SysfsPlatform):
+  """A SysfsPlatform implementation to be used for ChromeOS devices."""
+  def __init__(self, cri):
+    """Constructor.
+
+    Args:
+        cri: Chrome interface.
+    """
+    super(CrosSysfsPlatform, self).__init__()
+    self._cri = cri
+
+  def RunShellCommand(self, command):
+    return self._cri.RunCmdOnDevice(command.split())[0]
+
+  @staticmethod
+  def ParseStateSample(sample, time):
+    sample_stats = {}
+    for cpu in sample:
+      cstates = {'C0': time * 10 ** 6}
+      values = sample[cpu].splitlines()
+      num_states = len(values) / 3
+      names = values[:num_states]
+      times = values[num_states:2 * num_states]
+      latencies = values[2 * num_states:]
+      for i, state in enumerate(names):
+        if names[i] == 'POLL' and not int(latencies[i]):
+          # C0 state. Kernel stats aren't right, so calculate by
+          # subtracting all other states from total time (using epoch
+          # timer since we calculate differences in the end anyway).
+          # NOTE: Only x86 lists C0 under cpuidle, ARM does not.
+          continue
+        cstates['C0'] -= int(times[i])
+        if names[i] == '<null>':
+          # Kernel race condition that can happen while a new C-state gets
+          # added (e.g. AC->battery). Don't know the 'name' of the state
+          # yet, but its 'time' would be 0 anyway.
+          continue
+        cstates[state] = int(times[i])
+      sample_stats[cpu] = cstates
+    return sample_stats