module: add a gpufreq module for interacting with GPUs.

Add a module for controlling and interacting with GPUs. The module
currently supports kgsl/adreno based GPUs. This allows for querying
and setting the governor on the GPU, as well as seeing the frequencies
at which the the GPU can can operate.

Change-Id: I02bb997b51426ddaa13e1f8da375aa4c4a0d341a

devlib/module/gpufreq.py

@@ -0,0 +1,75 @@
+#    Copyright 2017 Google, ARM Limited
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+import re
+import json
+from devlib.module import Module
+from devlib.exception import TargetError
+from devlib.utils.misc import memoized
+
+class GpufreqModule(Module):
+
+    name = 'gpufreq'
+    path = ''
+
+    def __init__(self, target):
+        super(GpufreqModule, self).__init__(target)
+        frequencies_str = self.target.read_value("/sys/kernel/gpu/gpu_freq_table")
+        self.frequencies = map(int, frequencies_str.split(" "))
+        self.frequencies.sort()
+        self.governors = self.target.read_value("/sys/kernel/gpu/gpu_available_governor").split(" ")
+
+    @staticmethod
+    def probe(target):
+        # kgsl/Adreno
+        probe_path = '/sys/kernel/gpu/'
+        if target.file_exists(probe_path):
+            model = target.read_value(probe_path + "gpu_model")
+            if re.search('adreno', model, re.IGNORECASE):
+                return True
+        return False
+
+    def set_governor(self, governor):
+        if governor not in self.governors:
+            raise TargetError('Governor {} not supported for gpu {}'.format(governor, cpu))
+        self.target.write_value("/sys/kernel/gpu/gpu_governor", governor)
+
+    def get_frequencies(self):
+        """
+        Returns the list of frequencies that the GPU can have
+        """
+        return self.frequencies
+
+    def get_current_frequency(self):
+        """
+        Returns the current frequency currently set for the GPU.
+
+        Warning, this method does not check if the gpu is online or not. It will
+        try to read the current frequency and the following exception will be
+        raised ::
+
+        :raises: TargetError if for some reason the frequency could not be read.
+
+        """
+        return int(self.target.read_value("/sys/kernel/gpu/gpu_clock"))
+
+    @memoized
+    def get_model_name(self):
+        """
+        Returns the model name reported by the GPU.
+        """
+        try:
+          return self.target.read_value("/sys/kernel/gpu/gpu_model")
+        except:
+          return "unknown"