Add Hysteresis to pid controllers

Add hysteresis to pid controllers to lower pwm changes.
It is defaulted to 0 so it should be transparent
to any controller that choses not to implement it.
This is the same pattern used by the stepwise controller.

Tested-by: Unit tests passed

Change-Id: Ib47114285b0017258b7f77eaf067d310f95a0c60
Signed-off-by: James Feist <james.feist@linux.intel.com>

7 files changed, 142 insertions, 3 deletions

diff --git a/dbus/dbusconfiguration.cpp b/dbus/dbusconfiguration.cpp
index 3121623..7d01650 100644
--- a/dbus/dbusconfiguration.cpp
+++ b/dbus/dbusconfiguration.cpp
@@ -428,6 +428,24 @@ void init(sdbusplus::bus::bus& bus)
                     VariantToDoubleVisitor(), base.at("SlewNeg"));
                 info.pidInfo.slew_pos = variant_ns::visit(
                     VariantToDoubleVisitor(), base.at("SlewPos"));
+                double negativeHysteresis = 0;
+                double positiveHysteresis = 0;
+
+                auto findNeg = base.find("NegativeHysteresis");
+                auto findPos = base.find("PositiveHysteresis");
+                if (findNeg != base.end())
+                {
+                    negativeHysteresis = variant_ns::visit(
+                        VariantToDoubleVisitor(), findNeg->second);
+                }
+
+                if (findPos != base.end())
+                {
+                    positiveHysteresis = variant_ns::visit(
+                        VariantToDoubleVisitor(), findPos->second);
+                }
+                info.pidInfo.negativeHysteresis = negativeHysteresis;
+                info.pidInfo.positiveHysteresis = positiveHysteresis;
             }
         }
         auto findStepwise =
diff --git a/pid/ec/pid.hpp b/pid/ec/pid.hpp
index 779ced5..3ab64cd 100644
--- a/pid/ec/pid.hpp
+++ b/pid/ec/pid.hpp
@@ -31,6 +31,8 @@ typedef struct
     limits_t out_lim; // clamp of output
     double slew_neg;
     double slew_pos;
+    double positiveHysteresis;
+    double negativeHysteresis;
 } pid_info_t;
 
 double pid(pid_info_t* pidinfoptr, double input, double setpoint);
@@ -47,6 +49,8 @@ struct pidinfo
     ec::limits_t out_lim; // clamp of output
     double slew_neg;
     double slew_pos;
+    double positiveHysteresis;
+    double negativeHysteresis;
 };
 
 } // namespace ec
diff --git a/pid/pidcontroller.cpp b/pid/pidcontroller.cpp
index 7be6ceb..e3eaaff 100644
--- a/pid/pidcontroller.cpp
+++ b/pid/pidcontroller.cpp
@@ -20,6 +20,7 @@
 
 #include <algorithm>
 #include <chrono>
+#include <cmath>
 #include <iostream>
 #include <map>
 #include <memory>
@@ -38,8 +39,39 @@ void PIDController::process(void)
     // Get input value
     input = inputProc();
 
-    // Calculate new output
-    output = ec::pid(getPIDInfo(), input, setpt);
+    auto info = getPIDInfo();
+
+    // if no hysteresis, maintain previous behavior
+    if (info->positiveHysteresis == 0 && info->negativeHysteresis == 0)
+    {
+        // Calculate new output
+        output = ec::pid(info, input, setpt);
+
+        // this variable isn't actually used in this context, but we're setting
+        // it here incase somebody uses it later it's the correct value
+        lastInput = input;
+    }
+    else
+    {
+        // initialize if not set yet
+        if (std::isnan(lastInput))
+        {
+            lastInput = input;
+        }
+
+        // if reading is outside of hysteresis bounds, use it for reading,
+        // otherwise use last reading without updating it first
+        else if ((input - lastInput) > info->positiveHysteresis)
+        {
+            lastInput = input;
+        }
+        else if ((lastInput - input) > info->negativeHysteresis)
+        {
+            lastInput = input;
+        }
+
+        output = ec::pid(info, lastInput, setpt);
+    }
 
     // Output new value
     outputProc(output);
diff --git a/pid/pidcontroller.hpp b/pid/pidcontroller.hpp
index 9ed3be2..3d38c2a 100644
--- a/pid/pidcontroller.hpp
+++ b/pid/pidcontroller.hpp
@@ -49,6 +49,11 @@ class PIDController : public Controller
         return &_pid_info;
     }
 
+    double getLastInput(void)
+    {
+        return lastInput;
+    }
+
   protected:
     ZoneInterface* _owner;
 
@@ -57,4 +62,5 @@ class PIDController : public Controller
     ec::pid_info_t _pid_info;
     double _setpoint;
     std::string _id;
+    double lastInput = std::numeric_limits<double>::quiet_NaN();
 };
diff --git a/pid/util.cpp b/pid/util.cpp
index 9d666ef..a5936b0 100644
--- a/pid/util.cpp
+++ b/pid/util.cpp
@@ -34,6 +34,8 @@ void initializePIDStruct(ec::pid_info_t* info, const ec::pidinfo& initial)
     info->out_lim.max = initial.out_lim.max;
     info->slew_neg = initial.slew_neg;
     info->slew_pos = initial.slew_pos;
+    info->negativeHysteresis = initial.negativeHysteresis;
+    info->positiveHysteresis = initial.positiveHysteresis;
 }
 
 void dumpPIDStruct(ec::pid_info_t* info)
diff --git a/scripts/writepid.mako.cpp b/scripts/writepid.mako.cpp
index 1718bd1..852f4c0 100644
--- a/scripts/writepid.mako.cpp
+++ b/scripts/writepid.mako.cpp
@@ -27,6 +27,13 @@ std::map<int64_t, PIDConf> zoneConfig = {
                           setpoint = 0
                       else:
                           setpoint = details['set-point']
+
+                      neg_hysteresis = 0
+                      pos_hysteresis = 0
+                      if 'neg_hysteresis' in details['pid']:
+                          neg_hysteresis = details['pid']['neg_hysteresis']
+                      if 'pos_hysteresis' in details['pid']:
+                          pos_hysteresis = details['pid']['pos_hysteresis']
                   %>
                  ${setpoint},
                  {${details['pid']['sampleperiod']},
@@ -37,7 +44,9 @@ std::map<int64_t, PIDConf> zoneConfig = {
                   {${details['pid']['i_limit']['min']}, ${details['pid']['i_limit']['max']}},
                   {${details['pid']['out_limit']['min']}, ${details['pid']['out_limit']['max']}},
                   ${details['pid']['slew_neg']},
-                  ${details['pid']['slew_pos']}},
+                  ${details['pid']['slew_pos']},
+                  ${neg_hysteresis},
+                  ${pos_hysteresis}},
                 },
             },
             % endfor
diff --git a/test/pid_thermalcontroller_unittest.cpp b/test/pid_thermalcontroller_unittest.cpp
index 804d84a..ae5c769 100644
--- a/test/pid_thermalcontroller_unittest.cpp
+++ b/test/pid_thermalcontroller_unittest.cpp
@@ -8,6 +8,7 @@
 #include <gmock/gmock.h>
 #include <gtest/gtest.h>
 
+using ::testing::_;
 using ::testing::Return;
 using ::testing::StrEq;
 
@@ -143,4 +144,71 @@ TEST(ThermalControllerTest, InputProc_MultipleInputsMargin)
     EXPECT_CALL(z, getCachedValue(StrEq("fleeting1"))).WillOnce(Return(10.0));
 
     EXPECT_EQ(5.0, p->inputProc());
+}
+
+TEST(ThermalControllerTest, NegHysteresis_BehavesAsExpected)
+{
+
+    // This test verifies Negative hysteresis behaves as expected by
+    // crossing the setpoint and noticing readings don't change until past the
+    // hysteresis value
+
+    ZoneMock z;
+
+    std::vector<std::string> inputs = {"fleeting0"};
+    double setpoint = 10.0;
+    ec::pidinfo initial;
+    initial.negativeHysteresis = 4.0;
+
+    std::unique_ptr<PIDController> p = ThermalController::createThermalPid(
+        &z, "therm1", inputs, setpoint, initial, ThermalType::margin);
+    EXPECT_FALSE(p == nullptr);
+
+    EXPECT_CALL(z, getCachedValue(StrEq("fleeting0")))
+        .Times(3)
+        .WillOnce(Return(12.0))
+        .WillOnce(Return(9.0))
+        .WillOnce(Return(7.0));
+
+    EXPECT_CALL(z, addRPMSetPoint(_)).Times(3);
+
+    std::vector<double> lastReadings = {12.0, 12.0, 7.0};
+    for (auto& reading : lastReadings)
+    {
+        p->process();
+        EXPECT_EQ(p->getLastInput(), reading);
+    }
+}
+
+TEST(ThermalControllerTest, PosHysteresis_BehavesAsExpected)
+{
+    // This test verifies Positive hysteresis behaves as expected by
+    // crossing the setpoint and noticing readings don't change until past the
+    // hysteresis value
+
+    ZoneMock z;
+
+    std::vector<std::string> inputs = {"fleeting0"};
+    double setpoint = 10.0;
+    ec::pidinfo initial;
+    initial.positiveHysteresis = 5.0;
+
+    std::unique_ptr<PIDController> p = ThermalController::createThermalPid(
+        &z, "therm1", inputs, setpoint, initial, ThermalType::margin);
+    EXPECT_FALSE(p == nullptr);
+
+    EXPECT_CALL(z, getCachedValue(StrEq("fleeting0")))
+        .Times(3)
+        .WillOnce(Return(8.0))
+        .WillOnce(Return(13.0))
+        .WillOnce(Return(14.0));
+
+    EXPECT_CALL(z, addRPMSetPoint(_)).Times(3);
+
+    std::vector<double> lastReadings = {8.0, 8.0, 14.0};
+    for (auto& reading : lastReadings)
+    {
+        p->process();
+        EXPECT_EQ(p->getLastInput(), reading);
+    }
 }
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