pwr: Adds logic to enter power gating for the cpu model

If the CPU has been clock gated for a sufficient amount of time
(configurable via pwrGatingLatency), the CPU will go into the OFF
power state.  This does not model hardware, just behaviour.

Change-Id: Ib3681d1ffa6ad25eba60f47b4020325f63472d43
Reviewed-by: Andreas Sandberg <andreas.sandberg@arm.com>
Reviewed-on: https://gem5-review.googlesource.com/3969
Reviewed-by: Jason Lowe-Power <jason@lowepower.com>
Maintainer: Andreas Sandberg <andreas.sandberg@arm.com>

2 files changed, 14 insertions, 2 deletions

diff --git a/src/cpu/simple/atomic.cc b/src/cpu/simple/atomic.cc
index c47686abc..9039e6137 100644
--- a/src/cpu/simple/atomic.cc
+++ b/src/cpu/simple/atomic.cc
@@ -1,6 +1,6 @@
 /*
  * Copyright 2014 Google, Inc.
- * Copyright (c) 2012-2013,2015 ARM Limited
+ * Copyright (c) 2012-2013,2015,2017 ARM Limited
  * All rights reserved.
  *
  * The license below extends only to copyright in the software and shall
@@ -101,6 +101,9 @@ AtomicSimpleCPU::~AtomicSimpleCPU()
 DrainState
 AtomicSimpleCPU::drain()
 {
+    // Deschedule any power gating event (if any)
+    deschedulePowerGatingEvent();
+
     if (switchedOut())
         return DrainState::Drained;
 
@@ -163,6 +166,9 @@ AtomicSimpleCPU::drainResume()
             threadInfo[tid]->notIdleFraction = 0;
         }
     }
+
+    // Reschedule any power gating event (if any)
+    schedulePowerGatingEvent();
 }
 
 bool
diff --git a/src/cpu/simple/timing.cc b/src/cpu/simple/timing.cc
index d2cb6ee21..f57354d56 100644
--- a/src/cpu/simple/timing.cc
+++ b/src/cpu/simple/timing.cc
@@ -1,6 +1,6 @@
 /*
  * Copyright 2014 Google, Inc.
- * Copyright (c) 2010-2013,2015 ARM Limited
+ * Copyright (c) 2010-2013,2015,2017 ARM Limited
  * All rights reserved
  *
  * The license below extends only to copyright in the software and shall
@@ -94,6 +94,9 @@ TimingSimpleCPU::~TimingSimpleCPU()
 DrainState
 TimingSimpleCPU::drain()
 {
+    // Deschedule any power gating event (if any)
+    deschedulePowerGatingEvent();
+
     if (switchedOut())
         return DrainState::Drained;
 
@@ -146,6 +149,9 @@ TimingSimpleCPU::drainResume()
         }
     }
 
+    // Reschedule any power gating event (if any)
+    schedulePowerGatingEvent();
+
     system->totalNumInsts = 0;
 }