PID Objects & Algo
These are the PID controller implementations for fans,
and thermals. This also includes the PID algorithm used.
Change-Id: I30471fbf7a8a7ed65f78bf105970d62815fedc56
Signed-off-by: Patrick Venture <venture@google.com>
diff --git a/pid/pidthread.cpp b/pid/pidthread.cpp
new file mode 100644
index 0000000..38b2516
--- /dev/null
+++ b/pid/pidthread.cpp
@@ -0,0 +1,107 @@
+/**
+ * Copyright 2017 Google Inc.
+ *
+ * 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.
+ */
+
+#include <chrono>
+#include <map>
+#include <memory>
+#include <thread>
+#include <vector>
+
+#include "pidthread.hpp"
+
+#include "pid/controller.hpp"
+#include "sensors/sensor.hpp"
+
+
+static void ProcessThermals(std::shared_ptr<PIDZone> zone)
+{
+ // Get the latest margins.
+ zone->updateSensors();
+ // Zero out the RPM set point goals.
+ zone->clearRPMSetPoints();
+ // Run the margin PIDs.
+ zone->process_thermals();
+ // Get the maximum RPM set-point.
+ zone->determineMaxRPMRequest();
+}
+
+
+void PIDControlThread(std::shared_ptr<PIDZone> zone)
+{
+ int ms100cnt = 0;
+ /*
+ * This should sleep on the conditional wait for the listen thread to tell
+ * us it's in sync. But then we also need a timeout option in case
+ * phosphor-hwmon is down, we can go into some weird failure more.
+ *
+ * Another approach would be to start all sensors in worst-case values,
+ * and fail-safe mode and then clear out of fail-safe mode once we start
+ * getting values. Which I think it is a solid approach.
+ *
+ * For now this runs before it necessarily has any sensor values. For the
+ * host sensors they start out in fail-safe mode. For the fans, they start
+ * out as 0 as input and then are adjusted once they have values.
+ *
+ * If a fan has failed, it's value will be whatever we're told or however
+ * we retrieve it. This program disregards fan values of 0, so any code
+ * providing a fan speed can set to 0 on failure and that fan value will be
+ * effectively ignored. The PID algorithm will be unhappy but nothing bad
+ * will happen.
+ *
+ * TODO(venture): If the fan value is 0 should that loop just be skipped?
+ * Right now, a 0 value is ignored in FanController::input_proc()
+ */
+#ifdef __TUNING_LOGGING__
+ zone->initializeLog();
+#endif
+ zone->initializeCache();
+ ProcessThermals(zone);
+
+ while (true)
+ {
+ using namespace std::literals::chrono_literals;
+ std::this_thread::sleep_for(0.1s);
+
+ // Check if we should just go back to sleep.
+ if (zone->getManualMode())
+ {
+ continue;
+ }
+
+ // Get the latest fan speeds.
+ zone->updateFanTelemetry();
+
+ if (10 <= ms100cnt)
+ {
+ ms100cnt = 0;
+
+ ProcessThermals(zone);
+ }
+
+ // Run the fan PIDs every iteration.
+ zone->process_fans();
+
+#ifdef __TUNING_LOGGING__
+ zone->getLogHandle() << std::endl;
+#endif
+
+ ms100cnt += 1;
+ }
+
+ return;
+}
+
+