Support speed decrease events

A net decrease speed action determines the net decrease delta from each
group member's property value and requests a speed decrease of that
delta from the current target speed.

From all the requests for a speed decrease on a zone, only the lowest
net decrease is used from all the groups subscribed to decrease a zone's
speed. The new target speed is only decreased when no increase requests
exist and the resulting target is above the zone's floor speed,
otherwise the floor speed is set as the new target.

Resolves openbmc/openbmc#1626

Change-Id: Iaefa7b25c3f44691dd3ca4084bfddd3c1a504de9
Signed-off-by: Matthew Barth <msbarth@us.ibm.com>

1 files changed, 30 insertions, 5 deletions

diff --git a/control/zone.cpp b/control/zone.cpp
index 5ed0c3a..1ca0b81 100644
--- a/control/zone.cpp
+++ b/control/zone.cpp
@@ -97,6 +97,7 @@ Zone::Zone(Mode mode,
             std::get<actionPos>(event)(*this,
                                        std::get<groupPos>(event));
         }
+        //TODO openbmc/openbmc#1625 Start timer for fan speed decreases
     }
 }
 
@@ -105,11 +106,6 @@ void Zone::setSpeed(uint64_t speed)
 {
     for (auto& fan : _fans)
     {
-        //TODO openbmc/openbmc#1626 Move to control algorithm function
-        if (speed < _floorSpeed)
-        {
-            speed = _floorSpeed;
-        }
         fan->setSpeed(speed);
     }
 }
@@ -159,6 +155,35 @@ void Zone::requestSpeedIncrease(uint64_t targetDelta)
     _incSpeedDelta = 0;
 }
 
+void Zone::requestSpeedDecrease(uint64_t targetDelta)
+{
+    // Only decrease the lowest target delta requested
+    if (_decSpeedDelta == 0 || targetDelta < _decSpeedDelta)
+    {
+        _decSpeedDelta = targetDelta;
+    }
+
+    //TODO openbmc/openbmc#1625 Set decrease target speed when timer expires
+    // Only decrease speeds when no requested increases exist
+    if (_incSpeedDelta == 0)
+    {
+        // Target speed can not go below the defined floor speed
+        if ((_targetSpeed < _decSpeedDelta) ||
+            (_targetSpeed - _decSpeedDelta < _floorSpeed))
+        {
+            _targetSpeed = _floorSpeed;
+        }
+        else
+        {
+            _targetSpeed = _targetSpeed - _decSpeedDelta;
+        }
+        setSpeed(_targetSpeed);
+    }
+    // Clear decrease delta when timer expires
+    _decSpeedDelta = 0;
+    //TODO openbmc/openbmc#1625 Restart decrease timer
+}
+
 void Zone::getProperty(sdbusplus::bus::bus& bus,
                        const std::string& path,
                        const std::string& iface,