From 1c34ee20dfbbd557e394d61825232b10c0f3d37f Mon Sep 17 00:00:00 2001
From: Akash Bagdia <akash.bagdia@ARM.com>
Date: Tue, 9 Dec 2014 10:42:08 +0000
Subject: power: Low-power idle power state for idle CPUs

Add functionality to the BaseCPU that will put the entire CPU into a low-power
idle state whenever all threads in it are idle.
---
 src/cpu/base.cc | 27 +++++++++++++++++++++++++++
 1 file changed, 27 insertions(+)

(limited to 'src/cpu/base.cc')

diff --git a/src/cpu/base.cc b/src/cpu/base.cc
index 624843f42..0f9fe49ea 100644
--- a/src/cpu/base.cc
+++ b/src/cpu/base.cc
@@ -64,6 +64,7 @@
 #include "debug/SyscallVerbose.hh"
 #include "mem/page_table.hh"
 #include "params/BaseCPU.hh"
+#include "sim/clocked_object.hh"
 #include "sim/full_system.hh"
 #include "sim/process.hh"
 #include "sim/sim_events.hh"
@@ -355,6 +356,11 @@ BaseCPU::startup()
     if (params()->progress_interval) {
         new CPUProgressEvent(this, params()->progress_interval);
     }
+
+    // Assumption CPU start to operate instantaneously without any latency
+    if (ClockedObject::pwrState() == Enums::PwrState::UNDEFINED)
+        ClockedObject::pwrState(Enums::PwrState::ON);
+
 }
 
 ProbePoints::PMUUPtr
@@ -472,6 +478,27 @@ BaseCPU::findContext(ThreadContext *tc)
     return 0;
 }
 
+void
+BaseCPU::activateContext(ThreadID thread_num)
+{
+    // For any active thread running, update CPU power state to active (ON)
+    ClockedObject::pwrState(Enums::PwrState::ON);
+}
+
+void
+BaseCPU::suspendContext(ThreadID thread_num)
+{
+    // Check if all threads are suspended
+    for (auto t : threadContexts) {
+        if (t->status() != ThreadContext::Suspended) {
+            return;
+        }
+    }
+
+    // All CPU threads suspended, enter lower power state for the CPU
+    ClockedObject::pwrState(Enums::PwrState::CLK_GATED);
+}
+
 void
 BaseCPU::switchOut()
 {
-- 
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