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>

1 files changed, 11 insertions, 3 deletions

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