Decreases allowed based on all groups

For speed decreases to occur, all sensor groups involved with setting a
net decrease delta must be below their given t-control low values for
the associated zone. This handles the case where one or more sensor
groups' temperatures stabilize above their t-control low value, but one
or more other sensor groups' temperatures are below their t-control low
value which would result in speed decrease requests that could
eventually lead to fan speed oscillations.

Resolves openbmc/openbmc#2710

Change-Id: I382de5d3f9c3e631a332d49dfcb06e705ff6fc17
Signed-off-by: Matthew Barth <msbarth@us.ibm.com>

3 files changed, 58 insertions, 30 deletions

diff --git a/control/actions.hpp b/control/actions.hpp
index 55c8af8..c7356ab 100644
--- a/control/actions.hpp
+++ b/control/actions.hpp
@@ -230,41 +230,45 @@ auto set_net_decrease_speed(T&& state, T&& factor, uint64_t speedDelta)
             state = std::forward<T>(state)](auto& zone, auto& group)
     {
         auto netDelta = zone.getDecSpeedDelta();
-        std::for_each(
-            group.begin(),
-            group.end(),
-            [&zone, &state, &factor, &speedDelta, &netDelta](auto const& entry)
+        for (auto& entry : group)
+        {
+            try
             {
-                try
+                T value = zone.template getPropertyValue<T>(
+                        entry.first,
+                        std::get<intfPos>(entry.second),
+                        std::get<propPos>(entry.second));
+                // TODO openbmc/phosphor-fan-presence#7 - Support possible
+                // state types for comparison
+                if (value < state)
                 {
-                    T value = zone.template getPropertyValue<T>(
-                            entry.first,
-                            std::get<intfPos>(entry.second),
-                            std::get<propPos>(entry.second));
-                    // TODO openbmc/phosphor-fan-presence#7 - Support possible
-                    // state types for comparison
-                    if (value < state)
+                    if (netDelta == 0)
                     {
-                        if (netDelta == 0)
-                        {
-                            netDelta = ((state - value)/factor) * speedDelta;
-                        }
-                        else
-                        {
-                            // Decrease is the factor applied to the
-                            // difference times the given speed delta
-                            netDelta = std::min(
-                                netDelta,
-                                ((state - value)/factor) * speedDelta);
-                        }
+                        netDelta = ((state - value)/factor) * speedDelta;
+                    }
+                    else
+                    {
+                        // Decrease is the factor applied to the
+                        // difference times the given speed delta
+                        netDelta = std::min(
+                            netDelta,
+                            ((state - value)/factor) * speedDelta);
                     }
                 }
-                catch (const std::out_of_range& oore)
+                else
                 {
-                    // Property value not found, netDelta unchanged
+                    // No decrease allowed for this group
+                    netDelta = 0;
+                    break;
                 }
             }
-        );
+            catch (const std::out_of_range& oore)
+            {
+                // Property value not found, netDelta unchanged
+            }
+        }
+        // Update group's decrease allowed state
+        zone.setDecreaseAllow(&group, !(netDelta == 0));
         // Request speed decrease to occur on decrease interval
         zone.requestSpeedDecrease(netDelta);
     };
diff --git a/control/zone.cpp b/control/zone.cpp
index ffde46a..209d773 100644
--- a/control/zone.cpp
+++ b/control/zone.cpp
@@ -270,9 +270,17 @@ void Zone::requestSpeedDecrease(uint64_t targetDelta)
 
 void Zone::decTimerExpired()
 {
-    // Only decrease speeds when no requested increases exist and
-    // the increase timer is not running (i.e. not in the middle of increasing)
-    if (_incSpeedDelta == 0 && !_incTimer.running())
+    // Check all entries are set to allow a decrease
+    auto pred = [](auto const& entry) {return entry.second;};
+    auto decAllowed = std::all_of(_decAllowed.begin(),
+                                  _decAllowed.end(),
+                                  pred);
+
+    // Only decrease speeds when allowed,
+    // where no requested increases exist and
+    // the increase timer is not running
+    // (i.e. not in the middle of increasing)
+    if (decAllowed && _incSpeedDelta == 0 && !_incTimer.running())
     {
         auto requestTarget = getRequestSpeedBase();
         // Request target speed should not start above ceiling
diff --git a/control/zone.hpp b/control/zone.hpp
index bc08f48..406af13 100644
--- a/control/zone.hpp
+++ b/control/zone.hpp
@@ -89,6 +89,17 @@ class Zone
         }
 
         /**
+         * @brief Sets the decrease allowed state of a group
+         *
+         * @param[in] group - A group that affects speed decreases
+         * @param[in] isAllow - Allow state according to group
+         */
+        inline void setDecreaseAllow(const Group* group, bool isAllow)
+        {
+            _decAllowed[*(group)] = isAllow;
+        }
+
+        /**
          * @brief Sets a given object's property value
          *
          * @param[in] object - Name of the object containing the property
@@ -487,6 +498,11 @@ class Zone
         std::map<const Group, bool> _floorChange;
 
         /**
+         * @brief Map of groups controlling decreases allowed
+         */
+        std::map<const Group, bool> _decAllowed;
+
+        /**
          * @brief Map of group service names
          */
         std::map<const Group, std::vector<Service>> _services;